Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
2001-06-22
2003-09-02
Nguyen, Nam (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
C136S256000, C136S259000, C136S261000, C438S064000, C438S088000, C438S092000, C438S096000, C438S097000, C438S098000, C205S640000
Reexamination Certificate
active
06613973
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photovoltaic element, a producing method therefor, and a solar cell module. More particularly, the present invention relates to a photovoltaic element comprising a substrate having a through-hole formed therein through which electrodes arranged in the front and the back surfaces of the substrate are electrically connected, whereby a grid electrode is made unnecessary and the loss of incident light can be suppressed, a producing method therefore, and a solar cell module using the photovoltaic element. Further, the present invention relates to a photovoltaic element wherein a rectification layer having a rectification characteristic in the reverse direction to the voltage of the photo-electromotive force generated in a photoelectric conversion layer is formed to unit a bypass diode, to improve the processibility and lower the cost, a producing method therefore and a solar cell module using the photovoltaic element.
2. Related Background Art
Recently, in order to solve the problems of depletion of fossil fuel and the environmental problems induced by utilizing fossil fuel, solar energy has drawn attention as clean energy for the next generation.
Many photovoltaic elements used today comprise electrodes formed on a light-receiving face side and a non-light-receiving face side of a photoelectric conversion layer, a transparent electrode transmitting light formed on the light-receiving face side of the photoelectric conversion layer, and a metal electrode formed on the non-light-receiving face side of the photoelectric conversion layer.
The transparent electrode transmitting the light has a high electric resistance as compared with the metal electrode and causes an electric power loss at the time when an electric current flows in the transparent electrode. Hence, a grid electrode is used together for the purpose of lowering the electric power loss due to the transparent electrode. However, the grid electrode shuts out a part of sunlight incident upon the photoelectric conversion layer. Therefore, there occurs another problem that the electric power loss is caused by the grid electrode.
Therefore, many research and investigation institutes have been performing investigation and development of photovoltaic elements capable of suppressing an electric power loss caused by the transparent electrode to the minimum level and making it possible to omit the grid electrode.
Japanese Patent Application Laid-Open No. 6-151914 discloses a photovoltaic element having a structure in which a hole is formed in a photoelectric conversion layer with excimer laser and a light-receiving face electrode film formed on the light-receiving face side of the photoelectric conversion layer and a back electrode film formed in the non-light-receiving face side are electrically connected through the hole. The electric charge generated in the light-receiving face of the photoelectric conversion layer flows from the light-receiving face electrode film to the back electrode film through the hole, so that a grid electrode can be omitted, and the photovoltaic element has an advantage that the electric power loss attributed to the shadow of the grid electrode can be removed.
Further, in order to further simplify the production of the photovoltaic element in which a grid electrode is omitted, there are many ideas proposed relevant to the producing method in which the hole is formed in the initial stage of the production process and after that thin films are successively stacked, and the like.
Japanese Patent Application Laid-Open No. 8-64850 discloses a method of producing a photovoltaic element by successively forming an insulating layer on one side of a metal substrate having through-holes at constant intervals, a photoelectric conversion layer and further a transparent electrode layer on the other side, and a back electrode layer on the one side. Also, Japanese Patent Application Laid-Open No. 11-261086 proposes a method of producing a photovoltaic element by forming an insulating layer and a back electrode layer on a conductive substrate and then forming through-holes or recessed portions, and further successively stacking a photoelectric conversion layer and a transparent electrode layer.
The respective semiconductor layers of a photovoltaic element are generally formed by chemical vapor deposition, a sputtering method and the like in vapor phase or vacuum. In the case of forming the layers by these methods, in order to prevent a thin film composition adhered to the inner walls of a film formation apparatus from dropping on the processing face of a substrate or the like, it is preferable to carry out film formation in the state of facing downward the face of the substrate on which a layer is to be deposited.
However, in the method of producing a photovoltaic element disclosed in Japanese Patent Application Laid-Open No. 8-64850, layers are formed in the order on a non-light-receiving face side, a light-receiving face side, and a non-light-receiving face side of a substrate. For that, when film formation is carried out in the state of facing downward the face of the substrate on which a layer is to be deposited, the production process is divided into a first step of forming an insulating layer on the non-light-receiving face side of the substrate, a second step of forming a photoelectric conversion layer and a transparent electrode layer on the light-receiving face side of the substrate, and a third step of forming a back electrode layer on the non-light-receiving face side of the substrate. As a result, apparatuses are required to be made ready for respective steps. Like this, division of the process of forming the layers on the non-light-receiving face side of the substrate into two steps requires a long time necessary for production of the photovoltaic element, an increased number of apparatuses, and increased labor of workers. Also the cost of the photovoltaic element is elevated.
On the other hand, the method of producing the photovoltaic element proposed in Japanese Patent Application Laid-Open No. 11-261086 comprises forming through-holes after an insulating layer and a back electrode layer are stacked on a conductive substrate. For that, when the perforation process is carried out by a laser processing method or a mechanical processing method, it is required to prevent melting of a metal by heat and electric communication of the conductive substrate and the back electrode owing to the burr generated by the mechanical force.
Further, since the output voltage is generally insufficient in case of only one photovoltaic element, a plurality of photovoltaic elements connected in series are used. However, in case of connecting a plurality of photovoltaic elements in series, the following problems occur.
In the case some of elements become impossible to generate electric power owing to that the sun rays are shut by shadows of buildings, snow fall or the like, the whole generated voltage from normally working other elements is applied as inverse voltage to the elements which do not generate electric power. If the inverse voltage exceeds the withstand voltage of the elements, the probability of breakdown of the elements is elevated. In order to avoid that, bypass diodes are connected in parallel in the inverse direction for the respective photovoltaic elements connected in series. Japanese Patent Application Laid-Open No. 7-302923 proposes photovoltaic elements connected with bypass diodes having lead wires made of a metal foil material.
However, the photovoltaic elements disclosed in Japanese Patent Application Laid-Open No. 7-302923 require a work of connecting bypass diodes to an electrode of each one of the photovoltaic elements and thus the work is complicated and mass production in-a-line is made difficult.
Further, if bypass diodes are attached after formation of the respective layers constituting the photovoltaic elements, the flatness of the parts where the bypass diodes are formed is deteriorated. As a result, at the ti
Fukae Kimitoshi
Mukai Takaaki
Takabayashi Akiharu
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Mutschler Brian L
Nguyen Nam
LandOfFree
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