Claims:CLAIMS:
We Claim:
1. A method for synthesis of electrospun pure nanocomposite quasi-solid electrolytes for dye-sensitized solar cells, comprising:
dissolving poly(vinylidene fluoride-co-hexafluoropropylene) in an optimized solution of acetone and N,N-dimethylacetamide under constant stirring for 3 hours to form a transparent viscous polymer solution;
dispensing nanofibrous TiO2 of different weight percentages into said transparent viscous polymer solution under constant stirring for 5 hours to obtain a white viscous polymer solution;
electro-spinning said white viscous polymer solution using a syringe to obtain of electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes on a rotating drum collector;
extracting said electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes from said rotating drum collector; and
drying said electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes in an oven at 60°C for 24 h to remove remnant solvents, to obtain electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes with an average thickness of 70 to 120 mm,
Whereby said electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes exhibit high conductivity and high PCE for dye-sensitized solar cells.
2. The method for synthesis of electrospun pure nanocomposite quasi-solid electrolytes for dye-sensitized solar cells as claimed in claim 1, wherein 16 weight percentages of said poly(vinylidene fluoride-co-hexafluoropropylene) is dissolved in said optimized solution of acetone and N,N-dimethylacetamide and wherein said optimized solution comprises acetone and N,N-dimethylacetamide in volume ration of 7:3.
3. The method for synthesis of electrospun pure nanocomposite quasi-solid electrolytes for dye-sensitized solar cells as claimed in claim 1, wherein said different percentages of said nanofibrous TiO2 include weight percentages of 2%,4%,6%,8%.
4. The method for synthesis of electrospun pure nanocomposite quasi-solid electrolytes for dye-sensitized solar cells as claimed in claim 1, wherein said syringe utilized in said electro spinning apparatus consists of stainless steel 24 gauges needle.
5. The method for synthesis of electrospun pure nanocomposite quasi-solid electrolytes for dye-sensitized solar cells as claimed in claim 1, where in 6 weight percentages of said polymeric electrolyte membrane exhibits high conductivity which is suitable to fabricate DSSCs.
6. The method for synthesis of electrospun pure nanocomposite quasi-solid electrolytes for dye-sensitized solar cells as claimed in claim 1, wherein a gap of 12 cm is maintained between said needle tip and rotating drum collector and a rotation speed of said drum is kept at 500 rpm for the preparation. , Description:DESCRIPTION:
Field of the invention:
The present disclosure generally relates to field of photovoltaic devices, and in specific relates to electrospun nanocomposite quasi-solid electrolytes that exhibit high conductivity and high PCE for dye-sensitized solar cells.
Background of the invention:
Rapid increase in energy demand and rapid depletion of the fossil fuels leads to a great need for developing renewable energy resources. Among all forms of the renewable energy resources, solar energy is a clean and abundant source, which is directly converted into electricity through photovoltaic devices. Although the silicon solar cells have higher conversion efficiencies, the dye-sensitized solar cells (DSSCs) are considered as possible alternatives to conventional solar cells, due to their simple fabrication process, low-cost materials, and higher conversion efficiencies.

Even though higher efficiencies were recorded for the liquid electrolytes based DSSCs, the potential problems such as electrolyte leakage due to poor sealing, volatilization of the organic solvents, short-circuiting, and corrosion of electrodes, thereof limit the long time performance and the practical applications of the DSSCs. Therefore, much attention was given to improve the performance of DSSCs replacing the liquid electrolyte by using quasi-solid state or solid-state polymer electrolytes. Electrolytes are regarded as the heart of the dye-sensitized solar cell (DSSC) as they play a crucial role in conduction of ions between anode and cathode. In this regard, quasi-solid electrolytes are mostly preferred for DSSC applications. Owing to cost-effectiveness and easy processing methods, polymers are widely used for dielectric applications. Developing polymer composites with high dielectric constant is the recent on-going research globally, as they are suitable for electrolyte applications for many devices like Dye-sensitized solar cells, Lithium-ion batteries, super capacitors, etc. Several methods have been adopted to develop polymer composites with high dielectric constant. Among these methods, one method uses ceramic nano-materials composites such as Al2O3, ZnO, TiO2, SiO2, etc., to form polymer composites.

Poly(vinylidene fluoride) and its derivative copolymers are generally used in the preparation of polymer composites. Among them, poly-(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP is a semi-crystalline polymer with remarkable thermal and chemical stability. Owing to the highly electronegative property of fluorine, PVDF-HFP exhibits higher dielectric properties. Moreover, the dielectric behaviour of the polymer nanocomposite is influenced by the percentage of ceramic fillers dispersion and its microstructures. Incorporation of inorganic fillers results in high mass density, high rigidity and lowered mechanical strength.

Therefore, there is a need for suitable ceramic fillers with a high dielectric constant that facilitate better dissociation with polymer and hinder agglomeration in the polymer matrix. There is a need for fillers with high aspect ratio. There is a need for a composite with nanofibers that exhibits high conductivity suitable for DSSC applications.
Objectives of the invention:
The primary objective of the invention is to provide electrospun nanocomposite quasi-solid electrolytes that exhibit high conductivity and high PCE for dye-sensitized solar cells.

The other objective a method of preparation of electrospun nanocomposite quasi-solid electrolytes for dye-sensitized solar cells application.

Another objective of the invention is to synthesize a nanocomposite electrospun PVDF-HFP/ x wt.% (x = 2, 4, 6, 8)of nanofibrous TiO2 electrolyte membranes.

The other objective of the invention is to evaluate ion-conducting behaviour, relaxation dynamics and the photovoltaic performance of electrospun nanocomposite quasi-solid electrolytes.

Further objective of the invention is to utilize TiO2 as the ceramic filler which is synthesized by electro-spinning technique with high aspect ratio, and a high dielectric constant that can facilitate better dissociation with polymer and hinder agglomeration in the polymer matrix.
Summary of the invention:
The present disclosure proposes electrospun nanocomposite quasi-solid electrolytes for dye-sensitized solar cells and their preparation method thereof. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide electrospun nanocomposite quasi-solid electrolytes that exhibit high conductivity and high PCE for dye-sensitized solar cells.

According to an aspect, the invention provides a method for synthesis of electrospun pure nanocomposite quasi-solid electrolytes for dye-sensitized solar cells. The electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes exhibit high conductivity and high PCE for dye-sensitized solar cells. First, 16 weight percentages of poly(vinylidene fluoride-co-hexafluoropropylene) is dissolved in an optimized solution under constant stirring for 3 hours to form a transparent viscous polymer solution. In specific, the optimized solution comprises of acetone and N,N-dimethylacetamide in volume ratio of 7:3to form a transparent viscous polymer solution. Next, nanofibrous TiO2 of different weight percentages are dispensed into the transparent viscous polymer solution under constant stirring for 5 hours to obtain a white viscous polymer solution. The different percentages of the nanofibrous TiO2 include weight percentages of 2%, 4%, 6%, 8%.

Next, the white viscous polymer solution under goes electro spinning using a syringe of stainless steel with 24 gauge needle to obtain electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes on a rotating drum collector. Next, the electro spun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes are extracted from the rotating drum collector. Next, the electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes are dried in an oven at 60°C for 24 hours to remove remnant solvents, thereby obtains electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes with an average thickness of 70 to 120 mm. The polymeric electrolyte membrane of 6 weight percentages exhibits high conductivity which is suitable to fabricate DSSCs. A gap of 12 cm is maintained between the needle tip and the rotating drum collector and a rotation speed of said drum is kept at 500 rpm for the preparation.

Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.

FIG. 1 refers to a method of synthesis of electrospun pure nanocomposite quasi-solid electrolytes for dye-sensitized solar cells in accordance to an exemplary embodiment of the invention.

FIG. 2A depicts a nyquist plot of the nanocomposite electrospun polymeric membranes of PVDF-HFP/ x wt.% of nanofibrous TiO2 with redox cationic constituent Li+ in accordance to an exemplary embodiment of the invention.

FIG. 2B depicts a nyquist plot of the nanocomposite electrospun polymeric membranes of PVDF-HFP/ x wt.% of nanofibrous TiO2 with redox cationic constituent K+ in accordance to an exemplary embodiment of the invention.

FIG. 2C depicts a nyquist plot of the nanocomposite electrospun polymeric membranes of PVDF-HFP/ x wt.% of nanofibrous TiO2 with redox cationic constituent Na+ in accordance to an exemplary embodiment of the invention.

FIG. 2D depicts a nyquist plot of the nanocomposite electrospun polymeric membranes of PVDF-HFP/ x wt.% of nanofibrous TiO2 with redox cationic constituent TBA+ in accordance to an exemplary embodiment of the invention.

FIG. 3A depicts frequency dependence of complex conductivity spectra of electrospun polymeric membranes of PVDF- HFP/xwt.% of nanofibrous TiO2with cationic redox constituents Li+ in accordance to an exemplary embodiment of the invention.

FIG. 3B depicts frequency dependence of complex conductivity spectra of electrospun polymeric membranes of PVDF- HFP/xwt.% of nanofibrous TiO2 with cationic redox constituent K+ in accordance to an exemplary embodiment of the invention.

FIG. 3C depicts frequency dependence of complex conductivity spectra of electrospun polymeric membranes of PVDF- HFP/xwt.% of nanofibrous TiO2 with cationic redox constituent Na+ in accordance to an exemplary embodiment of the invention.

FIG. 3D depicts frequency dependence of complex conductivity spectra of electrospun polymeric membranes of PVDF- HFP/xwt.% of nanofibrous TiO2 with cationic redox constituent TBA+ in accordance to an exemplary embodiment of the invention.

FIG. 4A depicts dielectric constant s^tand dielectric loss s^ttof electrospun polymeric membranes of PVDF-HFP/xwt.% of nanofibrous TiO2 with redox cations Li+ in accordance to an exemplary embodiment of the invention.

FIG. 4B depicts dielectric constant s^tand dielectric loss s^ttof electrospun polymeric membranes of PVDF-HFP/xwt.% of nanofibrous TiO2with redox cations K+ in accordance to an exemplary embodiment of the invention.

FIG. 4C depicts dielectric constant s^tand dielectric loss s^ttof electrospun polymeric membranes of PVDF-HFP/xwt.% of nanofibrous TiO2with redox cations Na+ in accordance to an exemplary embodiment of the invention.

FIG. 4D depicts dielectric constant s^tand dielectric loss s^ttof electrospun polymeric membranes of PVDF-HFP/xwt.% of nanofibrous TiO2with redox cations TBA+ in accordance to an exemplary embodiment of the invention.

FIG. 5A depicts a J-V curve of fabricated DSSCs with electrospun pure PVDF-HFP membranes in accordance to an exemplary embodiment of the invention.

FIG. 5B depicts a J-V curve of fabricated DSSCs with nanocomposite PVDF-HFP/6wt.% of nanofibrous TiO2 polymeric electrolyte membranes in accordance to an exemplary embodiment of the invention.

FIG. 6 illustrates to an equivalent circuit of a single-diode model (SDM) of the solar cell in accordance to an exemplary embodiment of the invention.
Detailed invention disclosure:
Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.

The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide electrospun nanocomposite quasi-solid electrolytes that exhibit high conductivity and high PCE for dye-sensitized solar cells.

According to an exemplary embodiment of the invention, FIG. 1 refers to a method of synthesis of electrospun pure nanocomposite quasi-solid electrolytes for dye-sensitized solar cells. The electrospun pure and nanocomposite polymer fibrous membranes exhibit high conductivity and high PCE for dye-sensitized solar cells. At step 101, 16 weight percentages of poly(vinylidene fluoride-co-hexafluoropropylene) is dissolved in an optimized solution under constant stirring for 3 hours to form a transparent viscous polymer solution. In specific, the optimized solution comprises of acetone and N,N-dimethylacetamide in volume ratio of 7:3 to form a transparent viscous polymer solution. At step 102, nanofibrous TiO2 of different weight percentages are dispensed into the transparent viscous polymer solution under constant stirring for 5 hours to obtain a white viscous polymer solution. The different percentages of the nanofibrous TiO2 include weight percentages of 2%, 4%, 6%, 8%.

At step 103, the white viscous polymer solution is electrospun using a syringe of stainless steel with 24 gauge needle to obtain electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes on a rotating drum collector. At step 104, the electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes are extracted from the rotating drum collector. At step 105, the electro spun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes are dried in an oven at 60°C for 24 hours to remove remnant solvents, to thereby obtain the electrospun pure PVDF-HFP membranes and nanocomposite polymer fibrous membranes with an average thickness of 70 to 120 mm. The polymeric electrolyte membrane of 6 weight percentages (6 wt.%) exhibits high conductivity which is suitable to fabricate DSSCs. A gap of 12 cm is maintained between the needle tip and the rotating drum collector and a rotation speed of said drum is kept at 500 rpm for the preparation.

According to another exemplary embodiment of the invention, FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 2D depict nyquist plots of the nanocomposite electrospun polymeric membranes of PVDF-HFP/ x wt.% of nanofibrous TiO2 with distinct redox cationic constituents(Li+, K+, Na+, TBA+). Every electrospun pure PVDF-HFP and nanocomposite electrospun PVDF-HFP/ x wt.% of nanofibrous TiO2 polymeric membranes are dipped in a redox electrolyte. Due to which the dipped electrospun pure PVDF-HFP and nanocomposite electrospun polymeric membranes of PVDF-HFP/ x wt.% of nanofibrous TiO2 become quasi-solid electrolytes for DSSC applications, and are placed in between two electrodes in order to take impedance spectra reading. The redox electrolyte is formed by mixing 0.1M concentration of the respective iodide salts (i.e., LiI, NaI, KI, and TBAI) with 0.6M of BMII, 0.05M of I2 and 0.5M of TBP in a mixture of solvents of acetonitrile, EC, and PC, taken in the volume ratio 3:1:1.

The nyquist plots of all the electrolyte samples show a curved arc and a slanting spike. The arc observed in the high-frequency denotes the bulk resistance, and the spike present at the low-frequency elucidates the interfacial electrode-electrolyte double layer capacitance effect as the constant phase element. The x-intercept of the arc indicates the resistance. From the nyquist plots, it is observed that the bulk resistance decreases for the nanocomposite polymeric electrolyte membranes with the increase in the nanofibrous TiO2 concentration till 6 wt.%. The conductivity of the prepared electrolyte samples are evaluated by s = t/RA S/cm and presented in table 1.

Table 1:

From the table 1 it is observed that up to 6 wt.% of nanofibrous TiO2 value of conductivity increases, and for 8 wt.% of nanofibrous TiO2 the conductivity is reduced. The reduction in conductivity ascribes with the increase in crystallinity by the aggregation of fillers that affects the porosity of the polymeric membrane and thereby hinders the mobility of charge carriers. From table 1, it is observed that the redox constituents, the conductivity values of the prepared polymeric electrolyte samples vary with respect to cationic redox constituents as in order Li+, Na+, K+, and TBA+ respectively.

According to another exemplary embodiment of the invention, FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D depict the frequency dependence of complex conductivity spectra of electrospun polymeric membranes of PVDF- HFP/xwt.% of nanofibrous TiO2 (x = 0, 2, 4, 6, 8) with its respective cationic redox constituents (Li+, K+, Na+, TBA+ ). The observation is made from all log st verse log? plots of the polymeric electrolyte samples that conductivity raises with the increase in frequency. High dominance of electrode polarization is prevalent in the samples. The conductivity of the prepared nanocomposite polymeric electrolyte samples shows an enhanced conductivity with the addition of nanofibrous TiO2 till 6wt.% of the nanofibrous TiO2. The prepared nanocomposite polymeric electrolyte samples exhibit electrode polarization effect. The polarization effect at the interface of the electrode and the sample is found to exist at the low-frequency as well as at the mid-frequency region and so the onset of the DC-conductivity region is subtle for all the prepared samples.

Table 2:

In order to study the ion-conducting behaviour of the prepared samples that are dominant in electrode polarization, Random Barrier Model formulation is required to analyze. All the obtained parameters (s_dc,?_e,t_eand n) are shown in table 2 for PVDF-HFP/ x wt.% nanofibrous TiO2 (x = 0, 2, 4, 6, 8) with (Li+, K+, Na+, TBA+). From table 2 the observations are made that,s_dc,?_e and n valuesincrease with the addition of nanofibrous TiO2 concentration till 6 wt.% and decrease for 8 wt.%. The specific relaxation time (t_e) of the ionic-charge carriers required to overcome the randomly distributed free-energy barrier, reduces with increase in nanofibrous TiO2 concentration. The 6 wt.% of nanofibrous TiO2exhibits lowest relaxation time of 1.01 sec and has the highest ion-conducting value.

The prepared nanocomposite polymeric electrolytes sample reveal a characteristic frequency-exponent value (n) of 0.509, which is marginally higher than 0.5, that implies as light drift from stochastic hopping transport to an orderly 1-dimensional movement of ionic-charges inside the polymeric matrix. All the samples show a similar behaviour of conduction. The s_dc values of conductivity for the prepared nanocomposite PVDF-HFP/xwt.% of nanofibrous TiO2 varies with respect to the cationic redox constituents as in order Li+, Na+, K+, and TBA+ respectively. The order of the redox agents is due to bulky nature of cations in the electrolyte.

According to another exemplary embodiment of the invention, FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4D depict dielectric constant s^tand dielectric loss s^ttof electrospun polymeric membranes of PVDF-HFP/xwt.% of nanofibrous TiO2 (x = 0, 2, 4, 6, 8) with distinct redox cations (Li+, K+, Na+, TBA+ ) as a function of frequency. A high value of dielectric constant s^tis noticed at low-frequency regime that attributes to space charge polarization close to the interface between electrode and electrolyte. The value of dielectric constant becomes almost constant at higher frequencies represented as s_8 which might be due to the instantaneous polarization of ionic-charges for applied electric field varying with respect to time. Similarly, the same kind of variation is inferred in dielectric loss spectra s^tt.

A noticeable rise in s^t is detected with the addition of nanofibrous TiO2 in concentration till 6 wt.% and then the s^t is decreased for 8 wt.% of nanofibrous TiO2. Based on the nyquist plot and conductivity calculation, 6wt.% sample shows high-conductivity. For instance, table 3 shows dielectric relaxation parameters (?s, aHN and ßHN) obtained by Havriliak-Negami formalism for PVDF-HFP/x wt. % nanofibrous TiO2 (x = 0, 2, 4, 6, 8) with Li, Na, K and TBA as redox cations.

Table 3:

To analyze the non-Debye ion-conducting relaxation mechanism of the prepared nanocomposite polymeric electrolytes, Havriliak-Negami (HN) formulation is used. The obtained dielectric parameters (?s, aHN and ßHN) are shown in table 3. The prepared nanocomposite polymeric electrolytes show an enhanced high dielectric strength with the dispersion of nanofibrous TiO2 till 6 wt.% concentration and then decreased dielectric strength for 8 wt.%. Due to two types of shape parameters (aHN and ßHN), non-Debye relaxation behaviour of conductivity is shown. The average value of ?s obtained from RBM and HN formulations were shown in table 3. In all the sets of polymeric electrolyte samples, 6wt.% sample shows a non-Debye relaxation and a high value of ?s that attributes to high polarizability. The dielectric strength of the prepared electrospun PVDF-HFP/ x wt.% of nanofibrous TiO2 varies with respect to the cationic redox constituents arranged in an order as Li+ > Na+ > K+ > TBA+. Accordingly, Li-based PVDF-HFP with 6 wt.% of nanofibrous TiO2 polymeric electrolyte shows highest dielectric strength. The observed results are in good agreement with the ascertained complex conductivity results.

According to another exemplary embodiment of the invention, FIG. 5A and FIG. 5B depict the J-V curves 500 of fabricated DSSCs with electrospun pure PVDF-HFP, and fabricated DSSCs with nanocomposite PVDF-HFP/6wt.% of nanofibrous TiO2 polymeric electrolyte membranes respectively. The electrospun pure PVDF-HFP is dipped in various kinds of redox electrolyte solutions, and the nanocomposite PVDF-HFP/6wt.% of nanofibrous TiO2 polymeric electrolyte membranes are also dipped in various kinds of redox electrolyte solutions.

The redox electrolyte solutions such as electrolyte and pre-treated TiCl4 and TiO2 nanoparticles (P25) as photo-anodes, according to the fabrication procedure reported in literature. The photovoltaic performance data such as open-circuit voltage (Voc) and short-circuit current density (Jsc) were obtained from the J-V curves, whereas fill factor (FF) and power conversion efficiency (PCE) (?%) are calculated. Table 4 shows photovoltaic parameters of the fabricated DSSCs using electrospun pure PVDF-HFP and nanocomposite PVDF- HFP/6wt.% nanofibrous TiO2 polymeric electrolyte membranes with various cationic redox constituents (Li, Na, K, TBA).

Table 4:

The highest PCE of 7.02% is noticed for the fabricated DSSC with the prepared nanocomposite electrospun PVDF-HFP/6wt.% of polymeric membrane dipped in Li-based redox cationic solution. Moreover, the observed highest value of short-circuit current density (Jsc) (13.13 mA/cm2) for the Li-based attributes to the higher ionic conductivity of the electrolyte that proceeds with fast regeneration in the redox ingredients and successively followed by uninterrupted regeneration of the dye. The continuous regeneration of the dye and redox components restricts the negative effect of recombination during operation of DSSC. Furthermore, the pre-treated FTO acts as a blocking layer for the photo-anode and controls recombination that enhances short-circuit current density (Jsc) value. When Voc value is constant, some variations are noticed, which is due to the influence of the cations existing in the redox mediator. The cations present in the electrolytes need to altered the Fermi-energy level of the photo-anode. The performance of the DSSCs is in accordance with the size of the cations present in the electrolyte.

According to another exemplary embodiment of the invention, FIG. 6 refers to an equivalent circuit 600 of a single-diode model (SDM) of the solar cell. The J-V characteristic curves of the fabricated DSSCs are analyzed by an equivalent circuit of the single-diode model (SDM) of solar cell shown in FIG. 6. The photovoltaic parameters are obtained by employing symbiotic organisms search (SOS) algorithm. According to the equivalent circuit of SDM, the photo-current density (J) is expressed as,
J=J_SC-J_0 ?exp?(?^(q(V+R_s J)/nkT))- 1- (V+JR_s)/R_sh

Where Jo is the dark photo-current density, V is external applied voltage, Rs is series resistance, Rsh is shunt resistance, n is diode ideality factor, k is Maxwell Boltzmann constant and T is operating temperature. The J-V curves of the fabricated DSSCs are simulated by SDM equation. The root mean square error (RMSE) calculated between the experimental and calculated J-V data is minimized too obtain the photovoltaic parameters. The photovoltaic parameters obtained with a minimum value of RMSE during the minimization process are shown in table 4.

A lower value of Rs is observed for the DSSCs assembled with Li-based quasi-solid polymeric electrolyte membranes have increased the value of FF and the PCE. The obtained value of Rsh is found to be higher for Li-based compared to other fabricated DSSCs with Na, K and TBA. The lower value of Rs and higher Rsh value facilitates improvement in the photovoltaic performance. By the addition of nanofibrous TiO2 into the pure polymer PVDF-HFP, the value of Rs reduces and the value of Rsh increases. The observed values of Rs and Rsh might be due to the amorphousness of the polymeric electrolyte by the incorporation of nanofibrous TiO2 that ascertains rapid transfer of ionic-charge carriers in the fabricated DSSC. The lower value of Rs supports faster transport of ionic-charge carriers from the photo-anode material (TiO2) to the external circuit. The higher value of Rsh favours quicker regeneration of dye and electrolyte constituents.

Based on conductivity, the electrospun PVDF-HFP/6wt.% TiO2 is confirmed to be the highest ion-conducting electrolytes. The value of Rs is required to be low and the value of Rsh is required to be high to obtain a high value of FF and PCE. The fabricated DSSCs with Li-based pure electrospun PVDF-HFP and nanocomposite electrospun PVDF-HFP/6wt.% nanofibrous TiO2 observed to exhibit a less value of Rs and large value of Rsh compared to the fabricated DSSCs using other redox constituents in the prepared quasi-solid polymeric electrolytes.

Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, a method for preparation of electrospun nanocomposite quasi-solid electrolytes that exhibit high conductivity and high PCE for dye-sensitized solar cells is disclosed. The proposed electrospun nanocomposite quasi-solid electrolytes are synthesized nanocomposite electrospun PVDF-HFP/ x wt.% (x = 2, 4, 6, 8) of nanofibrous TiO2 electrolyte membranes. The nanofibrous TiO2 used as fillers exhibits high aspect ratio and a high dielectric constant that facilitates better dissociation with polymer and hinders agglomeration in the polymer matrix. The ion-conducting behaviour and relaxation dynamics of the prepared polymeric electrolyte membranes are found to exhibit non-Debye relaxation. The 6 wt.% of nanofibrous TiO2 exhibits lowest relaxation time and have the highest ion-conducting value.

It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.