PHOTOACTIVE CELLS WITH OPTICAL CONCENTRATORS
BACKGROUND

The present invention relates, in general, to photoactive cells. More particularly, the present invention relates to photoactive cells with optical concentrators.

A typical photoactive cell includes one or more photoactive elements that generate charge carriers when activated by electromagnetic radiation. Optical concentrators are often used in photoactive cells to concentrate incident electromagnetic radiation over photoactive elements. An optical concentrator may, for example, be in the form of a mirror that includes a reflective layer made of a highly-reflecting metal, such as silver or aluminum.
In addition, optical concentrators are required to have high reflectivity in the wavelength range required by a specific type of photoactive cell. For example, silicon-based photoactive cells provide good efficiency in the wavelength range of 300-1100 nm, whereas photoactive cells based on triple junction lll-V compounds respond in the wavelength range of 300-1800 nm. Since the reflectivity of silver dips around 400 nm and that of aluminum dips around 850 nm, neither of silver or aluminum is capable of providing high reflectivity in a continuous wavelength range. This has a negative impact on the electrical output of the photoactive cells. Furthermore, while silver has a higher reflectivity as compared to aluminum, it is expensive and gets tarnished easily.
In light of the foregoing discussion, there is a need for an optical concentrator that is capable of providing high reflectivity in a desired range of wavelength, and has a low cost, compared to conventional optical concentrators.

SUMMARY

An object of the present invention is to provide a photoactive cell (and manufacturing methods and systems thereof ).

Another object of the present invention is to provide an optical concentrator that is capable of providing high reflectivity in a desired range of wavelength.

Yet another object of the present invention is to provide an optical concentrator that has a low cost, compared to conventional optical concentrators.

Embodiments of the present invention provide a photoactive cell. The photoactive cell includes a base substrate, one or more photoactive elements arranged over the base substrate, at least two electrodes electrically connected with the photoactive elements, and one or more optical concentrators arranged above the photoactive elements. The photoactive elements generate charge carriers when activated by electromagnetic radiation, while the at least two electrodes collect the charge carriers generated by the photoactive elements. In addition, the optical concentrators concentrate electromagnetic radiation over the photoactive elements. The optical concentrators include a composite reflective layer of aluminum and silver that is capable of providing reflectivity in an extended range of wavelength, in accordance with an embodiment of the present invention.

In an embodiment of the present invention, the composite reflective layer includes an aluminum layer of thickness ranging from 70-110 nm and a silver layer of thickness ranging from 1-30 nm.
In another embodiment of the present invention, the composite reflective layer includes an aluminum layer of thickness ranging from 30-80 nm and a silver layer of thickness ranging from 30-80 nm.

In accordance with an embodiment of the present invention, the proportion of aluminum and silver in the composite reflective layer may be chosen, depending on the type of semiconductor material. This enhances the efficiency of the photoactive cell.

In an embodiment of the present invention, the optical concentrators include an inclined plane over which the composite reflective layer is formed. In another embodiment of the present invention, the optical concentrators include a sandwich structure formed by sandwiching the composite reflective layer between two transparent sheets. In yet another embodiment of the present invention, the optical concentrators include a smooth, polished sheet of aluminum over which a layer of silver is formed.

In accordance with an embodiment of the present invention, the photoactive cell also includes a transparent member positioned over the optical concentrators.

In accordance with an embodiment of the present invention, the base substrate, the photoactive elements, the at least two electrodes, and the optical concentrators are encapsulated with an encapsulant.

As mentioned above, the composite reflective layer has a high reflectivity in an extended range of wavelength, compared to silver or aluminum.

Moreover, the composite reflective layer has a low cost, due to reduction in usage of silver. This reduces the cost of the optical concentrators.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the scope of the claims, wherein like designations denote like elements, and in which:
FIG. 1 is a schematic diagram depicting a photoactive cell, in accordance with an embodiment of the present invention;
FIG. 2 depicts a system for manufacturing a photoactive cell, in accordance with an embodiment of the present invention; and
FIG. 3 depicts a method of manufacturing a photoactive cell, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

Various embodiments of the present invention provide a photoactive cell, and a method and system for manufacturing the photoactive cell. The photoactive cell includes a base substrate, one or more photoactive elements arranged over the base substrate, at least two electrodes electrically connected with the photoactive elements, and one or more optical concentrators arranged above the photoactive elements. The photoactive elements generate charge carriers when activated by electromagnetic radiation, while the at least two electrodes collect the charge carriers generated by the photoactive elements. In addition, the optical concentrators concentrate electromagnetic radiation over the photoactive elements. The optical concentrators include a composite reflective layer of aluminum and silver that is capable of providing reflectivity in an extended range of wavelength, in accordance with an embodiment of the present invention.

Referring now to figures, FIG. 1 is a schematic diagram depicting a photoactive cell 100, in accordance with an embodiment of the present invention.

Photoactive cell 100 includes a base substrate 102, one or more photoactive elements, shown as a photoactive element 104, at least two electrodes (not shown), and one or more optical concentrators, shown as an optical concentrator 106a and an optical concentrator 106b. Optical concentrator 106a and optical concentrator 106b are hereinafter referred as optical concentrators 106.

Base substrate 102 provides support to various components of photoactive cell 100, as shown. Base substrate 102 may be made of any material that is tolerant to moisture, Ultra Violet (UV) radiation, abrasion, and natural temperature variations. Examples of such materials include, but are not limited to, aluminum, steel, plastics and suitable polycarbonates.
In addition, base substrate 102 may have an electrically-insulated top surface. For example, base substrate 102 may be coated with a layer of electrically insulating material, such as anodized aluminum.

Photoactive element 104 is arranged over base substrate 102, as shown. Photoactive element 104 is capable of generating charge carriers when activated by electromagnetic radiation.

Photoactive element 104 may be made of a semiconductor material. Examples of semiconductors include, but are not limited to, monocrystalline silicon (c-Si), polycrystalline or multicrystalline silicon (poly-Si or mc-Si), ribbon silicon, cadmium telluride (CdTe), copper-indium diselenide (CulnSe2), combinations of III-V and II-VI elements in the periodic table that have photoelectric effect, copper indium/gallium diselenide (CIGS), gallium arsenide (GaAs), germanium (Ge), gallium indium phosphide (GalnP2), organic semiconductors such as polymers and small-molecule compounds like polyphenylene vinylene, copper phthalocyanine and carbon fullerenes, amorphous silicon (a-Si or a-Si:H), protocrystalline silicon, and nanocrystalline silicon (nc-Si or nc-Si:H).

The at least two electrodes are electrically connected with photoactive element 104, and are capable of collecting the charge carriers generated by photoactive element 104.

Optical concentrators 106 are arranged above photoactive element 104, as shown. Optical concentrators 106 are capable of concentrating electromagnetic radiation over photoactive element 104. The level of concentration may be varied depending on the shape and size of optical concentrators 106.

With reference to FIG. 1, a ray 108a, incident on optical concentrator 106a, undergoes reflection and falls over photoactive element 104. Similarly, a ray 108b, incident on optical concentrator 106b, undergoes reflection and falls over photoactive element 104.

Optical concentrators 106 include a composite reflective layer of aluminum and silver.
In an embodiment of the present invention, the composite reflective layer includes an aluminum layer of thickness ranging from 70-110 nm and a silver layer of thickness ranging from 1-30 nm.
In another embodiment of the present invention, the composite reflective layer includes an aluminum layer of thickness ranging from 30-80 nm and a silver layer of thickness ranging from 30-80 nm.

In accordance with an embodiment of the present invention, the composite reflective layer is capable of providing reflectivity in an extended range of wavelength. For example, a composite reflective layer including an aluminum layer of thickness ranging from 80-100 nm and a silver layer of thickness ranging from 5-20 nm silver provides high reflectivity in an extended range of wavelength, compared to a pure silver layer. This composite reflective layer also reduces the dip in reflectivity around 850 nm. In addition, the average reflectivity of the pure silver layer in the wavelength range of 200-1800 nm is 92.3%, while the average reflectivity of the composite reflective layer in the same wavelength range is 92.8%.

In accordance with an embodiment of the present invention, the composite reflective layer has an average reflectivity greater than 80 %.

In accordance with an embodiment of the present invention, the proportion of aluminum and silver in the composite reflective layer may be chosen, depending on the type of semiconductor material used in photoactive element 104.

In an embodiment of the present invention, optical concentrators 106 include an inclined plane over which the composite reflective layer is formed. The composite reflective layer may, for example, be formed by a vacuum coating process, such as thermal evaporation, sputtering, or ion-beam coating. Alternatively, the composite reflective layer may be formed by a process based on wet chemistry.

In another embodiment of the present invention, optical concentrators 106 include a sandwich structure formed by sandwiching the composite reflective layer between two transparent sheets.

In yet another embodiment of the present invention, optical concentrators 106 include a smooth, polished sheet of aluminum over which a layer of silver is formed.

In accordance with an embodiment of the present invention, photoactive cell 100 also includes a heat spreader (not shown) operatively coupled to photoactive element 104. The heat spreader spreads excessive heat generated during the operation of photoactive cell 100.

In accordance with an embodiment of the present invention, photoactive cell 100 also includes a transparent member (not shown) positioned over optica) concentrators 106. The transparent member protects photoactive element 104, the at least two electrodes and optical concentrators 106 from environmental damage, while allowing electromagnetic radiation incident on the transparent member to pass through. In addition, top and bottom surfaces of the transparent member may be coated with an anti-reflective coating, to reduce loss of electromagnetic radiation incident on photoactive cell 100.

In accordance with an embodiment of the present invention, base substrate 102, photoactive element 104, the at least two electrodes, and optical concentrators 106 are encapsulated with an encapsulant (not shown). The encapsulant may be made of any material that is tolerant to moisture, UV radiation, abrasion, and natural temperature variations. For example, the encapsulant may be made of silicones or suitable synthetic resins.

It is to be understood that the specific designation for photoactive cell 100 is for the convenience of reading and is not to be construed as limiting photoactive cell 100 to specific numbers, shapes, sizes, types, or arrangements of various components of photoactive cell 100. For example, a photoactive cell could include a plurality of photoactive elements. In such a case, the photoactive elements could be electrically connected in a predefined manner, as required. The predefined manner may, for example, be a series and/or parallel arrangement.

FIG. 2 illustrates a system 200 for manufacturing a photoactive cell, in accordance with an embodiment of the present invention. System 200 includes a photoactive-element arranging unit 202, a connecting unit 204, and an optical-concentrator arranging unit 206.
Photoactive-element arranging unit 202 arranges one or more photoactive elements over a base substrate, while connecting unit 204 electrically connects the photoactive elements in a predefined manner. The predefined manner may, for example, be a series and/or parallel arrangement, so as to obtain a desired electrical output.

In addition, connecting unit 204 electrically connects at least two electrodes with the photoactive elements.

As described earlier, the photoactive elements generate charge carriers when activated by electromagnetic radiation, while the at least two electrodes collect the generated charge carriers.

Optical-concentrator arranging unit 206 arranges one or more optical concentrators above the photoactive elements. The optical concentrators concentrate incident electromagnetic radiation over the photoactive elements.

In accordance with an embodiment of the present invention, the optical concentrators include a composite reflective layer of aluminum and silver that is capable of providing reflectivity in an extended range of wavelength.

In an embodiment of the present invention, the composite reflective layer includes an aluminum layer of thickness ranging from 70-110 nm and a silver layer of thickness ranging from 1-30 nm.
In another embodiment of the present invention, the composite reflective layer includes an aluminum layer of thickness ranging from 30-80 nm and a silver layer of thickness ranging from 30-80 nm.

In accordance with an embodiment of the present invention, system 200 includes an optical-concentrator forming unit (not shown) for forming optical concentrators, as desired.
In accordance with an embodiment of the present invention, the proportion of aluminum and silver in the composite reflective layer may be chosen, depending on the type of semiconductor material used in the photoactive elements.

In an embodiment of the present invention, the optical-concentrator forming unit forms the composite reflective layer over an inclined plane. The optical-concentrator forming unit may, for example, form the composite reflective layer by a vacuum coating process, such as thermal evaporation, sputtering, or ion-beam coating. Alternatively, the optical-concentrator forming unit may form the composite reflective layer by a process based on wet chemistry.

In another embodiment of the present invention, the optical-concentrator forming unit forms a sandwich structure by sandwiching the composite reflective layer between two transparent sheets.
In yet another embodiment of the present invention, the optical-concentrator forming unit obtains a smooth, polished sheet of aluminum and forms a layer of silver over the sheet of aluminum.

In accordance with an embodiment of the present invention, system 200 also includes a positioning unit (not shown) for positioning a transparent member over the optical concentrators. The positioning unit may, for example, be a pick-and-place unit that picks the transparent member, and aligns and places the transparent member over the optical concentrators.

In accordance with an embodiment of the present invention, system 200 further includes an encapsulating unit (not shown) for encapsulating various components of the photoactive cell with an encapsulant.

FIG. 2 is merely an example, which should not unduly limit the scope of the claims herein.

FIG. 3 illustrates a method of manufacturing a photoactive cell, in accordance with an embodiment of the present invention.
At step 302, one or more photoactive elements are arranged over a base substrate.

Thereafter, at step 304, the photoactive elements are electrically connected in a predefined manner. The predefined manner may, for example, be a series and/or parallel arrangement, so as to obtain a desired electrical output.

Subsequently, at step 306, at least two electrodes are electrically connected with the photoactive elements.

At step 308, one or more optical concentrators are arranged above the photoactive elements.
In accordance with an embodiment of the present invention, the optical concentrators include a composite reflective layer of aluminum and silver that is capable of providing reflectivity in an extended range of wavelength.

In an embodiment of the present invention, the composite reflective layer includes an aluminum layer of thickness ranging from 70-110 nm and a silver layer of thickness ranging from 1-30 nm.
In another embodiment of the present invention, the composite reflective layer includes an aluminum layer of thickness ranging from 30-80 nm and a silver layer of thickness ranging from 30-80 nm.

In accordance with an embodiment of the present invention, the proportion of aluminum and silver in the composite reflective layer may be chosen, depending on the type of semiconductor material used in the photoactive elements.

In accordance with an embodiment of the present invention, a step of forming an optical concentrator is performed. In an embodiment of the present invention, the composite reflective layer is formed over an inclined plane, to form an optical concentrator. In another embodiment of the present invention, an optical concentrator is formed by sandwiching the composite reflective layer between two transparent sheets. In yet another embodiment of the present invention, an optical concentrator is formed by obtaining a smooth, polished sheet of aluminum, and forming a layer of silver over the sheet of aluminum.

It should be noted here that steps 302-308 are only illustrative and other alternatives can also be provided where steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein. For example, one or more of the following steps may be added: a step of positioning a transparent member over the optical concentrators, and a step of encapsulating various components of the photoactive cell with an encapsulant.

Embodiments of the present invention provide a photoactive cell, and a method and system for manufacturing the photoactive cell. The photoactive cell includes an optical concentrator including a composite reflective layer of aluminum and silver.

The composite reflective layer has a high reflectivity in an extended range of wavelength.
In addition, the proportion of aluminum and silver in the composite reflective layer may be chosen, depending on the type of semiconductor material. This enhances the efficiency of the photoactive cell.

Moreover, the composite reflective layer has a low cost, due to reduction in usage of silver. This reduces the cost of the optical concentrators, and hence the cost of the photoactive cells so manufactured.

Furthermore, a plurality of photoactive cells could be electrically connected together to form a photoactive module. In one example, photoactive modules may be used to generate electricity on a small scale for home/office use. in another example, photoactive modules may be used to generate electricity for stand-alone electrical devices, such as automobiles and spacecraft. In yet another example, an array of photoactive modules could be used to generate electricity on a large scale for grid power supply.

In the description herein for the embodiments of the present invention, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of the embodiments of the present invention. One skilled in the relevant art will recognize, however, that an embodiment of the present invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of the embodiments of the present invention.

Reference throughout this specification to "one embodiment", "an embodiment", or "a specific embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of an embodiment of the present invention and not necessarily in all embodiments. Thus, respective appearances of the phrases "in one embodiment", "in an embodiment", or "in a specific embodiment" in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any specific embodiment of the present invention may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments of the present invention described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the present invention.

It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application.
As used in the description herein and throughout the claims that follow, "a", "an", and "the" includes plural references unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the present invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the present invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention.
Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of the embodiments of the present invention will be employed without a corresponding use of other features without departing from the scope and spirit of the present invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the present invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this present invention, but that the present invention will include any and all embodiments and equivalents falling within the scope of the appended claims.

CLAIMS WHAT IS CLAIMED IS:

1. A photoactive cell comprising:
a base substrate for providing support;
one or more photoactive elements arranged over the base substrate, the photoactive elements being capable of generating charge carriers when activated by electromagnetic radiation, the photoactive elements being electrically connected in a predefined manner;

at least two electrodes electrically connected with the photoactive elements, the at least two electrodes being capable of collecting the charge carriers generated by the photoactive elements;

one or more optical concentrators arranged above the photoactive elements, the optical concentrators being capable of concentrating electromagnetic radiation over the photoactive elements, the optical concentrators comprising a composite reflective layer of aluminum and silver, the composite reflective layer being capable of providing reflectivity in an extended range of wavelength.

2. The photoactive cell of claim 1, wherein the composite reflective layer comprises an aluminum layer of thickness ranging from 70-110 nm and a silver layer of thickness ranging from 1-30 nm.

3. The photoactive cell of claim 1, wherein the composite reflective layer comprises an aluminum layer of thickness ranging from 30-80 nm and a silver layer of thickness ranging from 30-80 nm.

4. The photoactive cell of claim 1, wherein the proportion of aluminum and silver in the composite reflective layer depends on the type of semiconductor material used in the photoactive elements.

5. The photoactive cell of claim 1, wherein the optical concentrators comprise an inclined plane over which the composite reflective layer is formed.

6. The photoactive cell of claim 1, wherein the optical concentrators comprise a sandwich structure formed by sandwiching the composite reflective layer between two transparent sheets.

7. The photoactive cell of claim 1, wherein the optical concentrators comprise a smooth, polished sheet of aluminum over which a layer of silver is formed.

8. The photoactive cell of claim 1 further comprising a transparent member positioned over the optical concentrators.

9. The photoactive cell of claim 1, wherein the base substrate, the photoactive elements, the at least two electrodes, and the optical concentrators are encapsulated with an encapsulant.

10. A photoactive cell substantially as herein above described in the specification with reference to the accompanying drawings.