Technical Field The present invention relates to a photoelectric conversion element, manufacturing method of the same and electronic equipment, and relates, for example, to a photoelectric conversion element suitable for use as a dye sensitized solar cell, a manufacturing method of the same and electronic equipment using the same. Background Art A solar cell, i.e., a photoelectric conversion element adapted to convert sunlight into electric energy, uses sunlight as a source of energy, thus making its impact on the global environment extremely small and holding promise for even more widespread use. Crystalline silicon-based solar cells using monocrystalline and polycrystalline silicons and amorphous silicon-based solar cells have been primarily used as solar cells. On the other hand, a dye sensitized solar cell proposed by Gratzel et al. in 1991 offers high photoelectric conversion efficiency and moreover can be manufactured at low cost because this solar cell does not require any large-scale manufacturing system as do the conventional silicon-based solar cells, thus drawing 2 attention (refer, for example, to Non-Patent Document 1). In general, this dye sensitized solar cell has a porous photoelectrode and a counter electrode opposed to each other. The porous photoelectrode is made of titanium oxide to which a photosensitizing dye is bound. The counter electrode is made, for example, of platinum. An electrolyte layer made of an electrolytic solution is filled between the porous photoelectrode and counter electrode. An electrolyte containing redox species such as iodine or iodide ion dissolved in a solvent is often used as an electrolytic solution. An additive is commonly added to this electrolytic solution to prevent reverse electron transfer from the porous photoelectrode to the electrolyte layer. Four-tert-butylpyridine (TBP) is the best known additive. Prior Art Documents Non-Patent Documents Non-Patent Document 1: Nature, 353, p.737 - 740, 1991 Non-Patent Document 2-. Inorg. Chem. 1996, 35, 1168 - 1178 Non-Patent Document 3: J. Chem. Phys. 124, 184902(2006) Summary of Invention 3 However, the types of additives added to the electrolytic solution of the dye sensitized solar cell are limited, making the range of choices extremely small and resulting in low degree of freedom in designing the electrolytic solution. In light of the foregoing, a problem to be solved by the present invention is to provide a photoelectric conversion element for use, for example, as a dye sensitized solar cell that has a wide range of choices of additives and moreover offers better characteristics than when 4-tert-butylpyridine is used as an additive. Another problem to be solved by the present invention is to provide a manufacturing method of a photoelectric conversion element that can manufacture the excellent photoelectric conversion element as described above. Still another problem to be solved by the present invention is to provide high performance electronic equipment using the excellent photoelectric conversion element as described above. The present inventor et al. diligently made experimental and theoretical studies to solve the above problems. As a result, it was discovered that there are many additives that offer better characteristics than 4- 4 tert-butylpyridine, an additive commonly added to the electrolyte layer. More specifically, we devised the present invention after having reached a conclusion that an additive having a pKa of 6.04 or more and 7.03 or less, i.e., a pKa falling within the range of 6.04 ≤ pKa < 7,3, offers better characteristics than 4-tert-butylpyridine. That is, in order to solve the above problems, the present invention is a photoelectric conversion element that has a structure in which an electrolyte layer is filled between a porous photoelectrode and counter electrode. An additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 is added to the electrolyte layer, and/or the additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 is adsorbed to the surface of at least either the porous photoelectrode or counter electrode facing the electrolyte layer. Further, the present invention is a manufacturing method of a photoelectric conversion element that includes a step of adding an additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 to an electrolyte layer filled between a porous photoelectrode and counter electrode, and/or a step of causing the additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 to be adsorbed to the surface of at least 'either the porous 5 photoelectrode or counter electrode facing the electrolyte layer. Still further, the present invention is electronic equipment that includes a photoelectric conversion element having a structure in which an electrolyte layer is filled between a porous photoelectrode and counter electrode. An additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 is added to the electrolyte layer, and/or the additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 is adsorbed to the surface of at least either the porous photoelectrode or counter electrode facing the electrolyte layer. In the present invention, basically any additive may be added to the electrolyte layer or adsorbed to the surface of at least either the porous photoelectrode or counter electrode so long as the additive has a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3. Here, Ka is the dissociation equilibrium constant of a conjugate acid in water. This additive is typically a pyridine-based additive or an additive having a heterocycle. Among specific examples of pyridine-based additives are 2- aminopyridine(2-NH2-Py), 4-methoxypyridine(4-MeO-Py) and 4-ethylpyridine(4-Et-Py). However, the pyridine-based additives are not limited thereto. On the other hand, 6 among specific examples of additives having a heterocycle are N-methylimidazole (MIm) , 2, 4-lutidine(24-Lu), 2,5- lutidine(25-Lu), 2,6-lutidine(26-Lu), 3,4-lutidine(34-Lu) and 3,5-lutidine(35-Lu). However, the additives having a heterocycle are not limited thereto. The additive includes at least one selected from among a group made up, for example, of 2-aminopyridine, 4-methoxypyridine, 4- ethylpyridine, N-methylimidazole, 2,4-lutidine, 2,5- lutidine, 2,6-lutidine, 3,4-lutidine and 3,5-lutidine. It should be noted that compounds having, in their molecule, a pyridine or heterocyclic compound structure, both having a pKa falling within the range of 6.04 A dye sensitized photoelectric conversion element' was manufactured in the following manner. A TiO2 dispersion solution in a paste form, i.e., 45 the raw material used to form the porous photoelectrode 3, was prepared by referring to "The State of the Art of Dye Sensitized Solar Cells" editorially supervised by Hironori Arakawa, 2001, and published by CMC Publishing. That is, 125 ml of titanium isopropoxide was gradually dripped into a 750 ml aqueous solution of 0.1 M of nitric acid while being agitated at room temperature. After the dripping, the mixture was transferred to a thermostatic bath at 80°C, and the agitation was continued for eight hours, as a result of which a whitish and opaque sol solution was obtained. This sol solution was allowed to cool down to room temperature and then filtered with a glass filter, after which a solvent was added to increase the volume to 7 00 ml. The obtained sol solution was transferred to an auto clave and allowed to undergo a hydrothermal reaction for 12 hours at 220°C, after which the solution was subjected to an ultrasonic process followed by a dispersion process. Next, this solution was concentrated at 40°C using an evaporator and prepared so that the TiO2 content was 20wt%. Polyethylene glycol equivalent to 20% of the mass of TiO2 (500000 in molecular weight) and TiO2 in an anatase form with a particle diameter of 200 nm and equivalent to 30% of the mass of TiO2 was added to this concentrated sol solution, and the 46 mixture was mixed evenly with a defoaming agitator to produce a TiO2 dispersion liquid in a paste form with higher viscosity. The above TiO2 dispersion liquid in a paste form was applied onto the FTO layer, i.e., the transparent electrode 2, by blade coating, thus forming a 5 mm-by-5 mm and 200 µm-thick fine particle layer. Then, the temperature was maintained at 500°C for 30 minutes, thus sintering the TiO2 fine particles on the FTO layer. An aqueous solution of 0.1 M titanium (IV) chloride TiCl4 was dripped onto the sintered TiO2 film, and then the film was maintained at room temperature for 15 hours, after which the film was cleaned and then fired again for 30 minutes at 500°C. Then, the TiO2 sintered body was irradiated with UV light for 30 minutes with a UV irradiation system, thus oxidatively decomposing impurities such as organic substances contained in the TiO2 sintered body by photocatalysis and removing these impurities. Then, a process adapted to improve the activity of the TiO2 sintered body was performed, as a result of which the porous photoelectrode 3 was obtained. A photosensitizing dye solution was prepared by dissolving, as a photosensitizing dye, 23.8 mg of fully purified Z907 in a 50 ml mixture solvent of acetonitrile 47 and butanol mixed at a 1:1 volume ratio. It should be noted that if the Z907 and dye A are used as photosensitizing dyes, a photosensitizing dye solution is prepared by dissolving, as photosensitizing dyes, 23.8 mg of fully purified Z907 and 2.5 mg of the dye A in a 50 ml mixture solvent of acetonitrile and butanol mixed at a 1:1 volume ratio. Next, the porous photoelectrode 3 was immersed in this photosensitizing dye solution for 24 hours at room temperature, thus allowing the photosensitizing dye to be held on the TiO2 fine particle surfaces. Next, the porous photoelectrode 3 was cleaned successively using an acetonitrile solution of 4-tert-butylpyridine and acetonitrile, after which the solvent was evaporated and the porous photoelectrode 3 dried at a dark location. The counter electrode 6 was formed by stacking, by sputtering, a 50 nm-thick chromium layer and a 100 nm-thick platinum layer on the FTO layer in which a 0.5 mm filling port had been formed in advance, and then coating the platinum layer with an aqueous isopropyl alcohol (2-propanol) solution of hydrogen chloroplatinate by spraying, followed by heating at 385°C for 15 minutes. Next, the transparent substrate 1 and opposed substrate 4 were arranged in such a manner that the 48 porous photoelectrode 3 and counter electrode 6 were opposed to each other. The outer peripheries thereof were sealed with a 30 µm-thick ionomer resin film and acryl-based UV-hardening resin. On the other hand, an electrolytic solution was prepared by dissolving 1.0 g of l-propyl-3-methylimidazolium iodide, 0.10 g of iodine I2 and 0.054 g of 2-NH2-Py as an additive in 2.0 g of 3-methoxypropionitrile (MPN). It should be noted that if the Z907 and dye A are used as photosensitizing dyes, an electrolytic solution is prepared, for example, by dissolving 0.030 g of sodium iodide Nal, 1.0 g of l-propyl-2,3-dimethylimidazolium iodide, 0.10 g of iodine I2 and 0.054 g of 2-NH2-Py as an additive' in 2.0 g of 3-methoxypropionitrile (MPN). This electrolytic solution was filled from the filling port of the dye sensitized photoelectric conversion element prepared in advance using a feed pump, and then the photoelectric conversion element was placed into a vacuum, thus removing air bubbles trapped therein. The electrolyte layer 7 is formed as described above. Next, the filling port was sealed with an ionomer resin film, acrylic resin and glass substrate, thus completing the dye sensitized photoelectric conversion element. 49 An electrolytic solution was prepared by using 4-MeO-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 4-Et-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using MIm as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 24-Lu as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 25- Lu as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as 50 in working example 1 in all other respects. An electrolytic solution was prepared by using 26-Lu as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 34-Lu as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 35-Lu as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared without any additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using TBP as an additive. A dye sensitized photoelectric conversion 51 element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 3> An electrolytic solution was prepared by using 4-pic as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 4> An electrolytic solution was prepared by using 4-COOMe-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 5> An electrolytic solution was prepared by using 4-CN-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 6> An electrolytic solution was prepared by using 4- NH2-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 7> An .electrolytic solution was prepared by using 4-52 MeNH-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 3-MeO-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 2-MeO-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 3-COOMe-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. . . 53 An electrolytic solution was prepared by using 3-Br-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using NMB as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 14> An electrolytic solution was prepared by using pyrazine as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using thiazole as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using Me- pyrazole as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. 54 Comparative Example 17> An electrolytic solution was prepared by using quinoline as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1. in all other respects. Comparative Example 18> An electrolytic solution was prepared by using isoquinoline as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 19> An electrolytic solution was prepared by using bpy as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 2 0> An electrolytic solution was prepared by using pyridazine as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 21> An electrolytic solution was prepared by using pyrimidine as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as 55 in working example 1 in all other respects. Comparative Example 22> An electrolytic solution was prepared by using acridine as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Comparative Example 23> An electrolytic solution was prepared by using 56-benzoquinoline as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Table 1 illustrates the pKa (water), photoelectric conversion efficiencies (Eff.) and internal resistances (Rs) in working examples 1 to 3, each using a pyridine- based additive, and comparative examples 1 to 12. Table 2 illustrates the pKa (water), photoelectric conversion efficiencies (Eff.) and internal resistances (Rs) in working examples 4 to 9, each using an additive having a heterocycle, and comparative examples 13 to 23. It is clear from Tables 1 and 2 that each of working examples 1 to 9, all using an additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3, offers an equivalent or higher photoelectric conversion efficiency (Eff.) and a lower internal resistance (Rs) than comparative example 2 56 using 4-tert-butylpyridine. Fig. 7 plots the photoelectric conversion efficiencies (Eff.) relative to pKa in working examples 1 to 9 and comparative examples 1 to 23. On the other hand, Fig. 8 plots the internal resistances (Rs) relative to pKa in working examples 1 to 9 and comparative examples 1 to 23. 57 (Table 1) 58 (Table 2) 59 A description will be given next of the dependence of the effects of the additives added to the electrolytic solution on the solvent species of the electrolytic solution. The effects of the additives were verified for each solvent having a different molecular weight. Here, 4- tert-butylpyridine (TBP) and 4-Et-Py (4-ethylpyridine) having relatively close pKa values were compared. The evaluation is as follows. The photoelectric conversion efficiency (Eff (4-Et-Py)) of the photoelectric conversion element using 4-Et-Py as an additive of the electrolytic solution and the photoelectric conversion efficiency (Eff (TBP)) of the photoelectric conversion element using TBP as an additive are measured for each solvent. Then, the difference between the two photoelectric conversion efficiencies AEff = Eff (4-Et-Py) - Eff (TBP) is used as an indicator. Four different solvents, namely, acetonitrile (AN), a mixture of acetonitrile (AN) and valeronitrile (VN) , methoxyacetonitrile (MAN) and 3-methoxypropionitrile (MPN), were used. Table 3 illustrates the molecular weight, Eff (4-Et-Py) , Eff (TBP) and AEff of each of the solvents. It should be noted, however, that the values reported in Solar Energy Materials & Solar Cells, 2003, 60 80, 167 were referred to as the Ef f (4-Et-Py) , Eff(TBP) and AEff values of acetonitrile (AN) . Fig. 9 plots the difference between the photoelectric conversion efficiencies AEff relative to the molecular weight of each of the solvents. (Table 3) It is clear from Table 3 and Fig. 9 that the range of molecular weight in which AEff>0, in other words, Eff(4-Et-Py) is greater than Eff(TBP), is 47.36 or more. It should be noted, however, that the molecular weight of 47.36 is an apparent molecular weight calculated using the volume fraction of a mixture of acetonitrile (AN) and valeronitrile (VN). From the above, it is clearly safe to say that it is effective to use an additive having a pKa falling within the range of 6.04 ≤ pKa ≤7 3 as an additive of the electrolytic solution for a solvent having a molecular weight of 47.36 or greater. As described above, an additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 is used as an 61 additive of the electrolytic solution forming the electrolyte layer 7 in the first embodiment. This contributes to equivalent or greater photoelectric conversion efficiency and equivalent or smaller internal resistance than those available with conventional dye sensitized photoelectric conversion elements using 4-tert-butylpyridine as an additive of the electrolytic solution, thus providing a photoelectric conversion element offering excellent photoelectric conversion characteristic. Further, a variety of additives have a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3, thus offering an extremely wide range of choices of additives. <2. Second Embodiment> [Dye Sensitized Photoelectric Conversion Element] This dye sensitized photoelectric conversion element differs from the counterpart according to the first embodiment in that at least an ionic liquid having electron pair accepting functional groups and an organic solvent having electron pair donating functional groups are used as solvents of the electrolytic solution forming the electrolyte layer 7. A cation forming the ionic liquid typically has an electron accepting functional group. The cation of the ionic liquid suitably includes an organic cation that 62 includes an aromatic amine cation having quaternary nitrogen atoms, and that has hydrogen atoms in the aromatic ring. Among examples of such an organic cation are imidazolium cation, pyridium cation, thiazolium cation and pyrazolium cation. However, the organic cation is not limited thereto. As the anion of the ionic liquid, an anion having a van der Waals volume of 7 6 A3 or more is suitably used, and that having a van der Waals volume of 100 A3 or more is more suitably used. Among specific examples of the ionic liquid having electron accepting functional groups are as follows. - EMImTCB: l-ethyl-3-methylimidazolium tetracyanoborate EMImTFSI: l-ethyl-3-methylimidazolium bis(trifluoromethanesulfone)imide EMImFAP: l-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate - EMImBF4: l-ethyl-3-methylimidazolium tetrafluoroborate Among specific examples of organic solvents having electron pair donating functional groups are as follows. MPN: 3-methoxypropionitrile (MPN) GBL: γ-butyrolactone DMF: N,N-dimethylformamide diglyme: diethylene glycol dimethyl ether triglyme: triethylene glycol dimethylether 63 tetraglyme: tetraethylene glycol dimethyl ether PhOAN: phenoxy acetonitrile PC: propylene carbonate aniline: aniline DMniline: N,N-dimethylaniline NBB: N-butylbenzimidazole TBP: tert-butylpyridine Specific examples of organic solvents having a tertiary nitrogen atom can be classified into five types as shown below. (1) Methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, ethylmethylamine, n-propylamine, iso-propyl, dipropylamine, n-butylamine, sec-butylamine and tert-butylamine (2) Ethylenediamine (3) Aniline and N,N-dimethylaniline (4) Formamide, N-methylformamide, N,N-dimethylformamide, acetoamide, N-methylacetoamide and N,N-dimethylacetoamide (5) N-methylpyrrolidone The organic solvents classified into types (1) to (4) are organic molecules with a molecular weight of 1000 or less having the following molecular framework represented by a general formula. (Chemical Formula 1) 64 It should be noted, however, that Rx, R2 and R3 in the formula are each one of substitution groups selected from among H, CnHm(n = 1 to 20, m= 3 to 41), phenyl group, aldehyde group and acetyl group. [Manufacturing Method of the Dye Sensitized Photoelectric Conversion Element] The manufacturing method of this dye sensitized photoelectric conversion element is identical to the counterpart according to the first embodiment except that at least an ionic liquid having electron pair accepting functional groups and an organic solvent having electron pair donating functional groups are used as solvents of the electrolytic solution forming the electrolyte layer 7. A dye sensitized photoelectric conversion element was manufactured in the following manner. The porous photoelectrode 3 holding a photosensitizing dye was formed on the transparent electrode 1, and the counter electrode 6 was formed on 65 the opposed electrode 4 in the same manner as in working example 1. Next, the transparent substrate 1 and opposed substrate 4 were arranged in such a manner that the porous photoelectrode 3 and counter electrode 6 were opposed to each other. The outer peripheries thereof were sealed with a 30 um-thick ionomer resin film and acryl-based UV-hardening resin. On the other hand, an electrolytic solution was prepared by dissolving 1.0 g of l-propyl-3-methylimidazolium iodide, 0.10 g of iodine I2 and 0.054 g of 2-NH2-Py as an additive in 2.0 g of a mixture solvent of EMImTCB and diglyme mixed at a 1:1 weight ratio. It should be noted that if the Z907 and dye A are used as photosensitizing dyes, an electrolytic solution is prepared, for example, by dissolving 0.030 g of sodium iodide Nal, 1.0 g of 1- propyl-2,3-dimethylimidazolium iodide, 0.10 g of iodine I2 and 0.054 g of 2-NH2-Py as an additive in 2.0 g of a mixture solvent of EMImTCB and diglyme mixed at a 1:1 weight ratio. This electrolytic solution was filled from the filling port of the dye sensitized photoelectric conversion element prepared in advance using a feed pump, and then the photoelectric conversion element was placed 66 into a vacuum, thus removing air bubbles trapped therein. The electrolyte layer 7 is formed as described above. Next, the filling port was sealed with an ionomer resin film, acrylic resin and glass substrate, thus completing the dye sensitized photoelectric conversion element. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and triglyme mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and tetraglyme mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and MPN mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. 67 An electrolytic solution was prepared by using a mixture solvent of EMImTCB and PhOAN mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and GBL mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and PC mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and aniline mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. 68 An electrolytic solution was prepared by using a mixture solvent of EMImTCB and DMF mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and DManiline mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and NBB mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and TBP mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. 69 An electrolytic solution was prepared by using a mixture solvent of EMImTFSI and triglyme mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImFAP and triglyme mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using diglyme as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using EMImTCB as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using MPN as a solvent. A dye sensitized photoelectric conversion 70 element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImTCB and PhAN (phenylacetonitrile) mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. Comparative Example 28> An electrolytic solution was prepared by using a mixture solvent of EMImBF4 (l-ethyl-3-methylimidazolium tetrafluoroborate) and triglyme mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. Comparative Example 2 9> An electrolytic solution was prepared by using a mixture solvent of EMImOTf (l-ethyl-3-methylimidazolium trifluorometanesulfonate) and triglyme mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. Comparative Example 30> 71 An electrolytic solution was prepared by using a mixture solvent of P222MOMTFSI (triethyl(methoxymethyl)phosphonium bis(trifluoromethylsufonyl)imide)) and triglyme mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. An electrolytic solution was prepared by using a mixture solvent of EMImBF4 and triglyme mixed at a 1:1 weight ratio as a solvent. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 10 in all other respects. Table 4 illustrates the results of finding the decrease in evaporation rate Zvapor of each of the mixture solvents of an ionic liquid and organic solvent in working examples 10 to 23 and comparative examples 27 to 30. It should be noted, however, that the weight percent of the organic solvent in each of the mixture solvents is 50wt%. Zvapor is defined as Zvap0r — [1~ (weight percent of organic solvent in mixture solvent) x (kmixture/kneat) x 100. kneat is the evaporation rate of the organic solvent alone. kmixture is the evaporation rate of the mixture solvent of 72 the ionic liquid and organic solvent. Both of them are found by TG (Thermo Gravimetry) - DTA (Differential Thermal Analysis) measurement. The larger Zvapor, the lower the volatility of the organic solvent component in the mixture solvent than that the organic solvent used alone. (Table 4) From Table 4, Zvapor is large and positive in working examples 10 to 31, showing that the volatility of the organic solvent component has declined as a result of the mixture of the ionic liquid and organic solvent. In 73 contrast, Zvapor is zero or negative in comparative examples 27 to 30, showing that the volatility of the organic solvent component has not declined as a result of the mixture of the ionic liquid and organic solvent. Fig. 10 illustrates TG-DTA curves of various solvents. As is clear from Fig. 10, the decrease in weight is significantly smaller when a mixture solvent of EMImTCB and MPN (weight percent of EMImTCB is 50wt%) is used (working example 13, curve (4) ) than when MPN is used alone (curve (5) ) . On the other hand, the decrease in weight is smaller when a mixture solvent of EMImTCB and GBL (weight percent of EMImTCB is 50wt%) is used (working example 15, curve (2)) than when GBL is used alone (curve (3)). Fig. 11 illustrates TG-DTA curves obtained when a mixture solvent of EMImTCB and diglyme (weight percent of EMImTCB is 50wt%) is used, when EMImTCB is used alone and when diglyme is used alone. It is clear from Fig. 11 that, when a mixture solvent of EMImTCB and diglyme is used, the decrease in weight is significantly smaller than when diglyme is used alone and is kept close to that when EMImTCB is used alone. Fig. 12 illustrates TG-DTA curves obtained when a mixture solvent of EMImTCB and triglyme (weight percent 74 of EMImTCB is 50wt%) is used (working example 11) , when EMImTCB is used alone and when triglyme is used alone. It is clear from Fig. 12 that, when a mixture solvent of EMImTCB and triglyme is used, the decrease in weight is significantly smaller than when triglyme is used alone and is kept close to that when EMImTCB is used alone. Fig. 13 illustrates TG-DTA curves obtained when a mixture solvent of EMImTCB and tetraglyme (weight percent of EMImTCB is 50wt%) is used (working example 12), when EMImTCB is used alone and when tetraglyme is used alone. It is clear from Fig. 13 that, when a mixture solvent of EMImTCB and tetraglyme is used, the decrease in weight is significantly smaller than when tetraglyme is used alone, and that the weight remains almost unchanged from when EMImTCB is used alone. Fig. 14 is a schematic diagram illustrating results of investigation on the relationship between the content of EMImTCB in a mixture solvent of EMImTCB and diglyme and the percentage of decrease in evaporation rate. Fig. 14 shows that when the content of EMImTCB is 15 weight percent or more, the evaporation rate decreases. A description will be given next of suitable cation and anion structures of the ionic liquid. First, as for the cation, an organic cation is suitable which includes 75 an aromatic amine cation having quaternary nitrogen atoms and which has hydrogen atoms in the aromatic ring. Among examples of such an organic cation are imidazolium cation, pyridium cation, thiazolium cation and pyrazolium cation. On the other hand, the anion can be defined by the van der Waals volume (electron cloud size) of the anion calculated based on computational science. Fig. 15 is a diagram plotting the percentages of decrease in evaporation rate of several anions (TCB-, TFSI-, OTf- and BF4~) relative to their van der Waals volumes. The Journal of The Electrochemical Society 002, 149(10), A1385-A1388 (2002) was referenced for the van der Waals volume of each of the anions. As the van der Waals volume of the TCB anion, that of the (C2H5)4B~ anion having a structure similar to that of the TCB anion was used. These pieces of data were fitted by a linear function. Letting the van der Waals volume be denoted by 'x' and the percentage of decrease in evaporation rate denoted by 'y,' the fitting formula is y = 0.5898x - 44.675. It is likely from Fig. 15 that the anions with a van der Waals volume of 100 A3 or more will suitably undergo a decrease in evaporation rate. A description will be given next of results of examination of the principle behind the decrease in 76 evaporation rate of a mixture solvent made up of an ionic liquid having electron pair accepting functional groups and an organic solvent having electron pair donating functional groups. In this mixture solvent, hydrogen bonds are formed between the electron pair accepting functional groups of the ionic liquid and the electron pair donating functional groups (ether group or amino group) of the organic solvent, thus making the solvent thermally stable. Fig. 16 illustrates an example thereof. As illustrated in Fig. 16, a hydrogen bond (shown by a dashed line) is formed between the electron pair accepting functional group (acidic proton) of the imidazolium cation in the ionic liquid and the ether group (-0-) of the diglyme molecule. As described above, it is possible to think that the evaporation rate of this mixture solvent decreases because the solvent becomes thermally stable as a result of the formation of hydrogen bonds between the ionic liquid and organic solvent. In particular, the more there are electron pair donating functional groups in each molecule of the organic solvent, the larger the percentage of decrease in evaporation rate. For example, Fig. 17 illustrates an example in which the organic solvent is triglyme. In this 77 example, a hydrogen bond is formed between each of the two electron pair accepting functional groups (acidic protons) of the imidazolium cation of the ionic liquid and each of the two ether groups of triglyme, thus making the mixture solvent thermally stable. Further, in this case, when a hydrogen bond is formed between one of the electron pair accepting functional groups of the imidazolium cation of the ionic liquid and one of the ether groups of triglyme, the other ether group of triglyme comes close to the other electron pair accepting functional group of the imidazolium cation of the ionic liquid. In other words, triglyme involves the imidazolium cation. This makes it easier for the other electron pair accepting functional group of the imidazolium cation of the ionic liquid to react with the other ether group of triglyme, thus forming a hydrogen bond therebetween. The second embodiment provides the following advantage in addition to the same advantage as offered by the first embodiment. That is, in the second embodiment, a mixture solvent made up of an ionic liquid having electron pair accepting functional groups and an organic solvent having electron pair donating functional groups is used as a solvent of the electrolytic solution forming the electrolyte layer 7, thus effectively suppressing the 78 evaporation of the electrolytic solution. Moreover, this mixture solvent is low in viscosity coefficient, thus making it possible to reduce the viscosity coefficient of the electrolytic solution and therefore providing a dye sensitized photoelectric conversion element offering excellent photoelectric conversion characteristic. <3. Third Embodiment> [Dye Sensitized Photoelectric Conversion Element] Fig. 18 is a sectional view illustrating a dye sensitized photoelectric conversion element according to a third embodiment. As illustrated in Fig. 18, a transparent electrode 12 is provided on one of the main surfaces of a transparent substrate 11 in this dye sensitized photoelectric conversion element. A porous photoelectrode 13 is provided on the transparent electrode 12 to which one or a plurality of types of photosensitizing dyes are bound (or adsorbed) . On the other hand, a counter electrode 14 is provided in such a manner as to be opposed to the transparent substrate 11. Then, the outer peripheries of the transparent substrate 11 and counter electrode 14 are sealed with a sealing agent 15. An electrolyte layer 16 made of an electrolytic solution is filled between the porous photoelectrode 13 provided 79 above the transparent substrate 11 and the counter electrode 14. The porous photoelectrode 13 includes metal/metal oxide fine particles 17 and is typically made of a material obtained by sintering the metal/metal oxide fine particles 17. The structure of the metal/metal oxide fine particle 17 is shown in detail in Fig. 19. As illustrated in Fig. 19, the metal/metal oxide fine particle 17 has a core-shell structure that includes a spherical metallic core 17a and a metal oxide shell 17b that wraps around the core 17a. One or a plurality of types of photosensitizing dyes are bound (or adsorbed) to the surface of the metal oxide shell 17b of the metal/metal oxide fine particle 17. A metal oxide such as titanium oxide (TiO2) , tin oxide (SnO2), niobium oxide (Nb2O5) or zinc oxide (ZnO) is, for example, used to form the shell 17b of the metal/metal oxide fine particle 17. Of these metal oxides, TiO2, and above all, TiO2 in an anatase form, should preferably be used. It should be noted, however, that the types of semiconductors that can be used are not limited thereto, and that two or more different semiconductors can be mixed or conjugated for use as necessary. Further, the metal/metal oxide fine particles 17 may be in any 80 form including a particle, tubular or bar form. Although the size of the metal/metal oxide fine particles 17 is not specifically limited, the average size of primary particles is generally 1 to 500 nm. Further, it is, above all, preferred that the average size should be 1 to 200 nm, and particularly preferred that the average size should be 5 to 100 nm. On the other hand, the size of the core 17a of the metal/metal oxide fine particles 17 is generally 1 to 200 nm. The same materials as used for the transparent substrate 1, transparent electrode 2, counter electrode 6 and electrolyte layer 7 of the dye sensitized photoelectric conversion element according to the first embodiment can be used for the transparent substrate 11, transparent electrode 12, counter electrode 14 and electrolyte layer 16. [Manufacturing Method of the Dye Sensitized Photoelectric Conversion Element] A description will be given next of the manufacturing method of this dye sensitized photoelectric conversion element. First, the transparent electrode 12 is formed on one of the main surfaces of the transparent substrate 11, for example, by sputtering. 81 Next, the porous photoelectrode 13 including the metal/metal oxide fine particles 17 is formed on the transparent electrode 12. After coating or printing the transparent electrode 12 with the metal/metal oxide fine particles 17, the porous photoelectrode 13 should preferably be fired to achieve electrical connection between the metal/metal oxide fine particles 17 and provide improved mechanical strength of the porous photoelectrode 13 and improved adhesion thereof to the transparent electrode 12. Next, a photosensitizing dye 18 is adsorbed to the porous photoelectrode 13 by immersing the transparent substrate 11 having the porous photoelectrode 13 formed thereon in a solution in which the photosensitizing dye 18 is dissolved in a given solvent. On the other hand, the counter electrode 14 is formed on the opposed substrate, for example, by sputtering. Next, the transparent substrate 11 having the porous photoelectrode 13 formed thereabove and the counter electrode 14 are arranged in such a manner that the porous photoelectrode 13 and counter electrode 14 are opposed to each other with a given spacing of 1 to 100 µm, and preferably 1 to 50 urn, therebetween. Then, the 82 sealing agent 15 is formed on the outer peripheries of the transparent substrate 11 and counter electrode 14 to produce a space in which the electrolyte layer is to be sealed. The electrolyte layer 16 is, for example, filled into this space via the filling port (not shown) formed in advance in the transparent electrode 11, after which the filling port is closed. The manufacturing method is identical to that according to the first embodiment in all other respects. The intended dye sensitized photoelectric conversion element is manufactured as described above. The metal/metal oxide fine particles 17 forming the porous photoelectrode 13 can be manufactured by a conventional well-known method (refer, for example, to Jpn. J. Appl. Phys. Vol. 46, No. 4B, 2007, pp. 2567 - 2570) . As an example, the outline of the manufacturing method of the metal/metal oxide fine particles 17 whose core 17a is made of Au and whose shell 17b is made of TiO2 is as follows. That is, dehydrated trisodium citrate is mixed into a heated 500 mL solution of 5 × 10_4MHAuCl4 and agitated. Next, a 2.5wt% of mercaptoundecanoic acid is added to an aqueous ammonium solution and agitated, and then the solution is added to an Au nanoparticle dispersion solution, after which the temperature of the 83 mixture is maintained constant for two hours. Next, 1 M of HC1 is added to adjust the pH of the solution to 3. Next, titanium isopropoxide and triethanol amine are added to the Au colloid solution under a nitrogen atmosphere. The metal/metal oxide fine particles 17 each of whose cores 17a is made of Au and each of whose shells 17b is made of TiO2 is manufactured as described above. [Operation of the Dye Sensitized Photoelectric Conversion Element] A description will be given next of the operation of the dye sensitized photoelectric conversion element. This dye sensitized photoelectric conversion element operates as a battery having the counter electrode 14 as a cathode and the transparent electrode 12 as an anode when struck with light. The operating principle is as described below. It should be noted that we assume here that FTO is used as the material of the transparent electrode 12, Au as the material of the core 17a and TiO2 as the material of the shell 17b of the metal/metal oxide fine particles 17 forming the porous photoelectrode 13, and that redox species I-/I3- is used as a redox couple. However, the materials of the transparent electrode 12 and porous photoelectrode 13 and the redox couple are not limited thereto. 84 When the photosensitizing dye 18, bound to the porous photoelectrode 13, absorbs the photons' that strike the porous photoelectrode 13 after having passed through the transparent substrate 11 and transparent electrode 12, the electrons in the photosensitizing dye 18 are excited from a ground state (HOMO) to an excited state (LUMO). The electrons thus excited are drawn out into the conduction band of TiO2 forming the shell 17b of the metal/metal oxide fine particles 17 forming the porous photoelectrode 13 via the electrical coupling between the photosensitizing dye 18 and porous photoelectrode 13, thus passing through the porous photoelectrode 13 and reaching the transparent electrode 12. In addition, when light strikes the surface of the Au-made core 17a of each of the metal/metal oxide fine particles 17, localized surface plasmons are excited, thus providing field enhancement effect. Then, a large number of electrons are excited by this enhanced electric field into the conduction band of TiO2 forming the shell 17b, thus passing through the porous photoelectrode 13 and reaching the transparent electrode 12. As described above, when the porous photoelectrode 13 is struck with light, the electrons generated by the excitation of the photosensitizing dye 18 reach the transparent electrode 85 12. In addition, the electrons excited into the conduction band of the TiO2 forming the shell 17b as a result of the excitation of localized surface plasmons on the surface of the core 17a of each of the metal/metal oxide fine particles 17 also reach the transparent electrode 12. This contributes to high photoelectric conversion efficiency. On the other hand, the photosensitizing dye 18 that has lost its electrons receives electrons from the reductant such as I- in the electrolyte layer 16, for example, as a result of the reaction shown below, thus producing an oxidant such as I3- (conjugate between I2 and I-) in the electrolyte layer 16. 21- → I2 + 2e- I2 + I- → I3- The oxidant thus produced reaches the counter electrode 14 as a result of dispersion and receives electrons from the counter electrode 14 by the reverse reaction of the above reaction, thus being reduced back to the original reductant. I3- → I2 + I- I2 + 2e- → 21- The electrons sent out from the transparent electrode 12 to external circuitry perform electrical 86 work in the external circuitry and then return to the counter electrode 14. As described above, optical energy is converted into electrical energy without making any change to the photosensitizing dye 18 or electrolyte layer 16. The third embodiment provides the following advantage in addition to the same advantage as offered by the first embodiment. That is, the porous photoelectrode 13 includes the metal/metal oxide fine particles 17 having a core-shell structure made up of the spherical metallic core 17a and the metal oxide shell 17b that wraps around the core 17a. This keeps the electrolyte of the electrolyte layer out of contact with the core 17a made of the metal of the metal/metal oxide fine particles 17 when the electrolyte of the electrolyte layer 16 is filled between this porous photoelectrode 13 and counter electrode 14, thus preventing the dissolution of the porous photoelectrode 13 by the electrolyte. This makes it possible to use, for example, gold, silver and copper having large surface plasmon resonance effect as a metal forming the core 17a of each of the metal/metal oxide fine particles 17, thus achieving sufficient surface plasmon resonance effect. Further, an iodine-based electrolyte can be used as the electrolyte of the 87 electrolyte layer 16. This provides a photoelectric conversion element offering high photoelectric conversion characteristic. High performance electronic equipment can be achieved by using this excellent photoelectric conversion element. <4. Fourth Embodiment> [Photoelectric Conversion Element] As shown in FIG. 20, the photoelectric conversion element according to a fourth embodiment has the same configuration as the dye sensitized photoelectric conversion element according to the third embodiment except that the photosensitizing dye 18 is not bound to the metal/metal oxide fine particles 17 forming the porous photoelectrode 13. [Manufacturing Method of the Photoelectric Conversion Element] The manufacturing method of this photoelectric conversion element is identical to that of the dye sensitized photoelectric conversion element according to the third embodiment except that the photosensitizing dye 18 is not adsorbed to the porous photoelectrode 13. [Operation of the Photoelectric Conversion Element] A description will be given next of the operation of this photoelectric conversion element. 88 This photoelectric conversion element operates as a battery having the counter electrode 14 as a cathode and the transparent electrode 12 as an anode when struck with light. The operating principle is as described below. It should be noted that we assume here that FTO is used as the material of the transparent electrode 12, Au as the material of the core 17a and TiO2 as the material of the shell 17b of each of the metal/metal oxide fine particles 17 forming the porous photoelectrode 13, and that redox species I-/I3- is used as a redox couple. However, the materials of the transparent electrode 12 and porous photoelectrode 13 and the redox couple are not limited thereto. When light strikes the surface of the Au-made core 17a of each of the metal/metal oxide fine particles 17 forming the porous photoelectrode 13 after having passed through the transparent substrate 11 and transparent electrode 12, localized surface plasmons are excited, thus providing field enhancement effect. Then, a large number of electrons are excited by this enhanced electric field into the conduction band of TiO2 forming the shell 17b, thus passing through the porous photoelectrode 13 and reaching the transparent electrode 12. On the other hand, the porous photoelectrode 13 89 that has lost its electrons receives electrons from the reductant such as I- in the electrolyte layer 16, for example, as a result of the reaction shown below, thus producing an oxidant such as I3- (conjugate between I2 and I-) in the electrolyte layer 16. 21- → I2 + 2e- I2 + I' → I3- The oxidant thus produced reaches the counter electrode 14 as a result of dispersion and receives electrons from the counter electrode 14 by the reverse reaction of the above reaction, thus being reduced back to the original reductant. I3- → I2 + I- I2 + 2e- → 21- The electrons sent out from the transparent electrode 12 to external circuitry perform electrical work in the external circuitry and then return to the counter electrode 14. As described above, optical energy is converted into electrical energy without making any change to the photosensitizing dye 18 or electrolyte layer 16. The fourth embodiment provides the same advantages as offered by the second embodiment. <5. Fifth Embodiment> 90 [Photoelectric Conversion Element] In this dye sensitized photoelectric conversion element, Z991 is used as the photosensitizing dye 18 adsorbed to the porous photoelectrode 3. This dye sensitized photoelectric conversion element is identical to the counterpart according to the first embodiment in all other respects. Fig. 21 illustrates the structural formula of the Z991. [Manufacturing Method of the Photoelectric Conversion Element] The manufacturing method of this dye sensitized photoelectric conversion element is identical to that of the dye sensitized photoelectric conversion element according to the first embodiment except that the Z991 is used as the photosensitizing dye 18 adsorbed to the porous photoelectrode 3. An electrolytic solution was prepared by using 4- MeO-Py as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 25- Lu as an additive. A dye sensitized photoelectric • 91 conversion element was manufactured in the same manner as in working example 1 in all other respects. An electrolytic solution was prepared by using 26-Lu as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. -Comparative Example 32> An electrolytic solution was prepared by using TBP as an additive. A dye sensitized photoelectric conversion element was manufactured in the same manner as in working example 1 in all other respects. Table 5 illustrates the pKa (water), photoelectric conversion efficiencies (Eff.) and internal resistances (Rs) in working examples 24 to 26 and comparative example 32. It is clear from Table 5 that each of working examples 24 to 26, all using an additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3, offers a higher photoelectric conversion efficiency (Eff.) and a lower internal resistance (Rs) than comparative example 32 using 4-tert-butylpyridine. 92 (Table 5) The fifth embodiment provides the same advantages as offered by the first embodiment. Although the embodiments and working examples of the present invention have been described above, the present invention is not limited to the above embodiments and working examples. Instead, the present invention may be modified in various ways based on technical ideas. For example, the numerical values, structures, configurations, shapes, materials and so on cited in the above embodiments and working examples are merely examples, and numerical values, structures, configurations, shapes, materials and so on different therefrom may be used as necessary. Description of Reference Numerals 1.. .Transparent substrate, 2 ... Transparent electrode, 3...Porous photoelectrode, 4...Opposed substrate, 5...Transparent conductive layer, 6...Counter electrode, 93 7.. .Electrolyte layer, 11... Transparent substrate, 12...Transparent electrode, 13...Porous photoelectrode, 14...Counter electrode, 15...Sealing agent, 16...Electrolyte layer, 17...Metal/metal oxide fine particles, 17a...Core, 17b...Shell, 18 ... Photosensitizing dye 94 Claims 1. A photoelectric conversion element having a structure in which an electrolyte layer is filled between a porous photoelectrode and counter electrode, wherein an additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 is added to the electrolyte layer, and/or wherein the additive having a pKa falling within the range of 6.04 ≤ pKa≤ 7.3 is adsorbed to the surface of at least either the porous photoelectrode or counter electrode facing the electrolyte layer. 2. The photoelectric conversion element of claim 1, wherein the additive is a pyridine-based additive or an additive having a heterocycle. 3. The photoelectric conversion element of claim 2, wherein the additive comprises at least one selected from among a group made up of 2-aminopyridine, 4-methoxypyridine, 4-ethylpyridine, N-methylimidazole, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, 3,4-lutidine and 3,5-lutidine. 4. The photoelectric conversion element of claim 1, wherein 95 the electrolyte layer comprises an electrolytic solution, and wherein the molecular weight of the solvent of the electrolytic solution is 47.36 or more. 5. The photoelectric conversion element of claim 4, wherein the solvent is 3-methoxypropionitrile, methoxyacetonitrile or a mixture of acetonitrile and valeronitrile. 6. The photoelectric conversion element of claim 1 being: a dye sensitized photoelectric conversion element in which a photosensitizing dye is bound to the porous photoelectrode. 7 . (Amended) The photoelectric conversion element of claim 6, wherein the dye is a polypyridine complex having a saturated hydrocarbon group whose carbon number is 6 or more . 8. (Amended) The photoelectric conversion element of claim 1, wherein the porous photoelectrode comprises fine particles made of a semiconductor. 9. (Amended) The photoelectric conversion element 96 of claim 1, wherein the electrolyte layer comprises an electrolytic solution, and wherein the solvent of the electrolytic solution includes an ionic liquid having electron pair accepting functional groups and an organic solvent having electron pair donating functional groups. 10. (Amended) The photoelectric conversion element of claim 1, wherein the porous photoelectrode comprises fine particles, each having a metallic core and a metal oxide shell wrapped around the core. 11. (Amended) A manufacturing method of a photoelectric conversion element comprising a step of: adding an additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 to an electrolyte layer filled between a porous photoelectrode and counter electrode; and/or a step of: causing the additive having a pKa falling within the range of 6.04 ≤ pKa≤ 7.3 to be adsorbed to the surface of at least either the porous photoelectrode or counter electrode facing the electrolyte layer. 12. (Amended) The manufacturing method of a photoelectric conversion element of claim 11, wherein 97 the additive is a pyridine-based additive or an additive having a heterocycle. 13. (Amended) The manufacturing method of a photoelectric conversion element of claim 12, wherein the additive comprises at least one selected from among a group made up of 2-aminopyridine, 4-methoxypyridine, 4-ethylpyridine, N-methylimidazole, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, 3,4-lutidine and 3,5-lutidine. 14. (Amended) The manufacturing method of a photoelectric conversion element of claim 11, wherein when a structure is formed in which the electrolyte layer made of an electrolytic solution is filled between the porous photoelectrode and counter electrode, a solvent having a molecular weight of 47.36 or more is contained in the electrolytic solution. 15. (Amended) The manufacturing method of a photoelectric conversion element of claim 14, wherein the solvent is 3-methoxypropionitrile, methoxyacetonitrile or a mixture of acetonitrile and valeronitrile. 16. (Amended) The manufacturing method of a photoelectric conversion element of claim 11 further comprising 98 a step of binding a photosensitizing dye to the porous photoelectrode. 17. (Amended) The manufacturing method of a photoelectric conversion element of claim 11, wherein the porous photoelectrode comprises fine particles made of a semiconductor. 18. (Amended) The manufacturing method of a photoelectric conversion element of claim 11, wherein when a structure is formed in which the electrolyte layer made of an electrolytic solution is filled between the porous photoelectrode and counter electrode, an ionic liquid having electron pair accepting functional groups and an organic solvent having electron pair donating functional groups are contained in the electrolytic solution. 19. (Amended) The manufacturing method of a photoelectric conversion element of claim 11, wherein the porous photoelectrode comprises fine particles, each having a metallic core and a metal oxide shell wrapped around the core. 20. (New) Electronic equipment comprising at least: a photoelectric conversion element, the photoelectric conversion element having a structure in 99 which an electrolyte layer is filled between a porous photoelectrode and counter electrode, wherein an additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 is added to the electrolyte layer, and/or wherein the additive having a pKa falling within the range of 6.04 ≤ pKa ≤ 7.3 is adsorbed to the surface of at least either the porous photoelectrode or counter electrode facing the electrolyte layer.