The application relates to a solar photovoltaic device, and more particularly to a solar photovoltaic device having a solar cell body with improved photovoltaic-converting efficiency.
This application claims the right of priority based on TW application Ser. No. 098111844, filed “Apr. 9, 2009”, entitled “SOLAR PHOTOVOLTAIC DEVICE” and the contents of which are incorporated herein by reference in its entirety.
Because of the shortage of the petroleum energy resource and the promotion of the environment protection, people continuously and actively study the art related to the replaceable energy resource and the regenerative energy resource in order to reduce the dependence of petroleum energy resource and the influence on the environment. The solar cell is an attractive candidate among those replaceable energy resources and the regenerative energy resource because the solar cell can directly convert solar energy into electricity. In addition, there are no injurious substances like carbon oxide or nitride generated during the process of generating electricity so there is no pollution to the environment.
Referring to
Accordingly, the tandem solar cell 100 can absorb wide spectrum range of the incident light which is from 300 nm to 1800 nm, wherein the wavelength of the incident light absorbed by the bottom cell 120 is the longest.
The present application provides a solar photovoltaic device which can improve photovoltaic-converting efficiency of the tandem solar cell.
The present application provides a solar photovoltaic device including a solar cell body, a window layer located on the solar cell body, and a current collection layer located on the window layer. The current collection layer includes a patterned structure, wherein the patterned structure exposes a portion of the window layer.
In accordance with an embodiment of the present application, the band gap (Eg) of the above current collection layer is larger than or equal to that of the window layer.
In accordance with an embodiment of the present application, the material of the above current collection layer includes GaP, AlN, AlInP, ITO, ZnP, IZO, AZO, GZO, or ZnO.
In accordance with an embodiment of the present application, the above current collection layer can be a transparent conductive layer and the material thereof includes ITO, ZnP, IZO, AZO, GZO, or ZnO.
In accordance with an embodiment of the present application, the reflectivity of the above current collection layer is less than 40%.
In accordance with an embodiment of the present application, the doping of the above current collection layer is n-type and the dopant thereof includes Si, Te, Sb, Ge, or other suitable dopants.
In accordance with an embodiment of the present application, the doping of the above current collection layer is p-type and the dopant thereof includes C, Mg, Zn, or other suitable dopants.
In accordance with an embodiment of the present application, the pattern of the above patterned structure is selected from a group consisting of grid, stripe, and finger.
In accordance with an embodiment of the present application, the solar photovoltaic device further includes a patterned front contact and a cap layer. The patterned front contact is located on at least a part of the current collection layer and the window layer. The cap layer is located between the current collection layer and the patterned front contact and between the window layer and the patterned front contact wherein the current collection layer is etched to form a pattern which is different from that of the patterned front contact.
In accordance with an embodiment of the present application, the solar photovoltaic device further includes an anti-reflective layer located on the surface of the current collection layer.
In accordance with an embodiment of the present application, the ratio of the openings area of the above current collection layer is between 0.3 and 0.7, better between 0.5 and 0.7.
In accordance with an embodiment of the present application, the thickness of the above current collection layer is between 200 Å and 8000 Å.
In accordance with an embodiment of the present application, the solar photovoltaic device further includes a transparent conductive layer on the current collection layer and an anti-reflective layer on the transparent conductive layer.
In accordance with an embodiment of the present application, when a transparent conductive layer is located on the current collection layer, the above a transparent conductive layer and the current collection layer include the same or different patterned structures. In addition, the above solar photovoltaic device further includes a patterned front contact located on at least a part of the current collection layer and the transparent conductive layer, and a cap layer located between the current collection layer and the patterned front contact and between the transparent conductive layer and the patterned front contact
In accordance with another embodiment of the present application, the solar photovoltaic device includes a solar cell body, a window layer located on the solar cell body, and a current collection layer located on the window layer, wherein the resistance of the current collection layer is lower than that of the window layer and the current collection layer includes a patterned structure to expose a portion of the window layer.
In accordance with another embodiment of the present application, the pattern of the above patterned structure is selected from a group consisting of grid, stripe, and finger.
In accordance with another embodiment of the present application, the ratio of the openings area of the above current collection layer is between 0.542 and 0.7.
In accordance with another embodiment of the present application, the solar photovoltaic device further includes a transparent conductive layer on the current collection layer, wherein the transparent conductive layer and the current collection layer include the same or different patterned structures.
Based on the above description, the top cell of the solar photovoltaic device is partially covered by a current collection layer so the current-collecting efficiency of the solar photovoltaic device can be improved. Because the transparent conductive layer can absorb a part of incident light having long wavelength, however, the current density generated by the bottom cell can not match with that generated by the top cell so the series current of the solar photovoltaic device is reduced. Forming openings at the current collection layer can have the current of the top cell matched with that of the bottom cell and increase current-collecting efficiency.
The foregoing aspects and many of the attendant purpose, technology, characteristic, and function, of this application will become more readily appreciated as the same becomes better understood by reference to the following embodiments detailed description, when taken in conjunction with the accompanying drawings
The embodiments of present application will be described in detail and sketched in figures.
Referring to
The transmittance of the conventional current collection layer is poor in long wavelength range like larger than 1100 nm. If the top surface of the solar cell body 210 is thoroughly covered by the conventional current collection layer for increasing current-collecting efficiency, it results in that most incident light having long wavelength is absorbed by the conventional current collection layer and can not reach the bottom cell. It should be noted that the ratio of the openings area of the current collection layer 230 in this embodiment is between 0.3 and 0.7, better between 0.5 and 0.7, preferably between 0.542 and 0.7. The above ratio of the openings area is the ratio of the area of the light-facing surface 222 of the window layer 220 not covered by the current collection layer 230 and the patterned front contact 250 (it can be grid or other pattern as the drawing shows) to the total area of the light-facing surface 222. The term of “between” mentioned above includes the meaning of “equal”. When the solar photovoltaic device 200 is a tandem solar cell, the current collection layer 230 of which the ratio of the openings area is between 0.3 and 0.7 can allow the incident light having long wavelength to enter into the bottom cell (not shown) of the solar photovoltaic device 200 so the bottom cell can generate the current density matching with that of the top cell.
The band gap of the current collection layer 230 is larger than or equal to that of the window layer 220 in this embodiment. The material of the window layer 220 can be the semiconductor material like GaP, AlN, or AlInP, or the transparent conductive material like ITO, ZnP, IZO, AZO, GZO, or ZnO. In addition, the current collection layer 230 having high transmittance, of which reflectivity is less than 40% for example, can enable the incident light to penetrate the current collection layer 230 easily and to be absorbed by the solar cell body 210. The material of the current collection layer 230 can include GaP, AlN, AlInP, ITO, ZnP, IZO, AZO, GZO, or ZnO. The current collection layer 230 can be deposited on the window layer 220 by Metal Organic Chemical Vapor Deposition (MOCVD) and be etched to form the openings. In general, the thicker the thickness of the current collection layer 230 is, the better the conductivity thereof is. The transmittance of the current collection layer 230, however, can be reduced. Considering the conductivity and transmittance, the thickness of the current collection layer 230 can be between 200 Å and 8000 Å. On the other hand, if the doping of the current collection layer 230 is n-type, the dopant thereof can be Si, Te, Sb, or Ge. If the doping of the current collection layer 230 is p-type, the dopant thereof can be C, Mg, or Zn.
Referring to
Furthermore, the pattern of the patterned structure of the current collection layer 230 can be different from that of the patterned front contact 250 and the pattern thereof is selected from a group consisting of grid, stripe, and finger. As
The solar photovoltaic device is not limited in the above drawings. For instance, the embodiments shown in
In summary, because the doping concentration of the current collection layer 230 is higher than that of the window layer 220 and the ratio of the openings area of the current collection layer 230 is between 0.3 and 0.7, the current collection layer 230 partially covering the light-facing surface 222 of the window layer 220 can increase the current-collecting efficiency of the solar photovoltaic device 200 and reduce the use of the patterned front contact 250. Thus, the shaded area of the patterned front contact 250 can be reduced. Moreover, the incident light having long wavelength can penetrate the openings of the current collection layer 230 and reach the bottom cell to increase the current density of the bottom cell so the photovoltaic-converting efficiency can be increased.
Although the present application has been explained above, it is not the limitation of the range, the sequence in practice, the material in practice, or the method in practice. Any modification or decoration for present application is not detached from the spirit and the range of such.
Number | Date | Country | Kind |
---|---|---|---|
098111844 | Apr 2009 | TW | national |
200910132804.6 | Apr 2009 | CN | national |