Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
2000-03-14
2001-06-26
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
C136S256000, C136S258000, C136S259000, C257S432000, C257S434000, C257S437000, C257S436000, C257S053000
Reexamination Certificate
active
06252157
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an amorphous silicon-based thin film photovoltaic device.
It is well known to the art that a thin film photovoltaic device having an amorphous silicon-based photovoltaic unit, e.g., a solar battery, lacks stability. To be more specific, when the carrier excited by irradiated light is recombined within amorphous semiconductor layer, the bonding state of silicon atom is changed by the energy released in the step of the recombination, with the result that new recombination centers are formed in the forbidden band. As a result, the film property such as photo-conductivity of the photovoltaic silicon layer is lowered, eventually conversion efficiency will be lowered. This phenomenon appears most prominently when energy is consumed within the device as is in an open circuit state. Incidentally, it is known to the art that, if the deteriorated photovoltaic device is subjected to a heat treatment at approximately 150° C., the change noted above is moderated so as to restore again the conductivity. This phenomenon is called Staebler-Wronski effect.
It is known to the art to form, for example, a buffer layer between the p-layer and the i-layer of a pin-type photovoltaic unit in order to suppress deterioration of the amorphous silicon-based thin film photovoltaic device. However, it is difficult to form accurately the buffer layer having an appropriate impurity concentration.
On the other hand, the glass substrate material used in the conventional amorphous silicon-based thin film photovoltaic device is selected in view of improving only initial characteristics or cost. In other words, deterioration of characteristics is not taken into account in selecting the glass substrate material. Such being the situation, the deterioration of characteristics remains to be a practical problem in the conventional photovoltaic device, though it may be possible to obtain satisfactory characteristics in the laboratory level.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a stable amorphous silicon-based thin film photovoltaic device using a suitable glass substrate material and, thus, exhibiting good initial characteristics while suppressing deterioration of characteristics.
According to the present invention, there is provided an amorphous silicon-based thin film photovoltaic device, comprising a glass substrate, and a laminate structure formed on the glass substrate and consisting of a transparent electrode, a semiconductor layer containing an amorphous silicon-based semiconductor and a back electrode, wherein the glass substrate has a transmittance of 88 to 90% for light having a wavelength of 700 nm and 84 to 87% for light having a wavelength of 800 nm.
In the amorphous silicon-based thin film photovoltaic device of the present invention, it is desirable for the transparent electrode to be formed of a transparent conductive oxide having an irregular structure and for the back electrode to be formed of a light reflective metal or a stack of a transparent conductive oxide and a light reflective metal. The particular construction is called an optical confinement structure. The light reflective metal used in the present invention includes, for example, Ag, Au, Al, Cu, Pt and alloys thereof. The transparent conductive oxide used in the present invention includes, for example, ITO, SnO
2
and ZnO.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 4066815 (1978-01-01), Olink et al.
patent: 5077133 (1991-12-01), Cheng
patent: 5449413 (1995-09-01), Beauchamp et al.
patent: 5656098 (1997-08-01), Ishikawa et al.
patent: 849808 (1998-06-01), None
patent: 0849808 A2 (1998-06-01), None
patent: WO 98/11031 (1998-03-01), None
Patent Abstracts of Japan, Abstract for JP 9-162435, Jun. 1997.
Patent Abstracts of Japan, Abstract for JP 57-149845, Sep. 1982.
Diamond Alan
Hogan & Hartson L.L.P.
Kaneka Corporation
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