Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
2001-12-05
2004-01-27
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
C136S256000, C136S252000, C429S111000, C257S431000, C257S043000, C257S040000
Reexamination Certificate
active
06683244
ABSTRACT:
BACKGROND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoelectric conversion element.
2. Description of the Prior Art
From the approximately past ten years ago, great attention has been paid to solar cells (photoelectric conversion element) employing silicon as a power source which is harmless to the environment. As for these solar cells employing silicon, a monocrystalline silicon type solar cell is known, which is used in artificial satellites or the like. In addition, as solar cells for practical applications, there are known a solar cell employing polycrystalline silicon (single crystal silicon) and a solar cell employing amorphous silicon. These solar cells have already been practically used in industrial and household applications.
However, since these solar cells employing silicon require high manufacturing cost and a great deal of energy in manufacturing thereof, thus these solar cells are not yet established as an energy-saving power source.
Further, since a dye-sensitized wet solar cell such as those disclosed in Japanese laid-open patent applications No. H01-220380, No. H05-504023 and No. H06-511113 employs an electrolyte of which vapor pressure is extremely high, there is a problem in that the electrolyte volatilizes.
For solving the problem, a perfect solid type dye-sensitized solar cell has been proposed (K. Tennakone, G. R. R. A. Kumara, I. R. M. Kottegoda, K. G. U. Wijiayantha, and V. P. S. Perera: J. Phys. D: Appl. Phys. 31(1998)1492). This solar cell is composed of an electrode on which a TiO
2
layer is laminated and a p-type semiconductor layer provided on the TiO
2
layer. However, this solar cell has a problem in that the p-type semiconductor layer is liable to penetrate the TiO
2
layer to short-circuit the electrode.
Further, in the above proposal, CuI is used as a constituent material of the p-type semiconductor. The solar cell employing the CuI has a problem in that a generated current is lowered due to its deterioration caused by the increase in the crystal grain size of CuI and the like.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a solid type dye-sensitized photoelectric conversion element which is excellent in photoelectric conversion efficiency and which can be manufactured at a low cost.
In order to achieve the above object, the present invention is directed to a photoelectric conversion element, which comprises a first electrode; a second electrode arranged opposite to the first electrode; an electron transport layer arranged between the first electrode and the second electrode, at least a part of the electron transport layer being formed into porous; a dye layer which is in contact with the electron transport layer; a hole transport layer arranged between the electron transport layer and the second electrode; and short-circuit preventing means for preventing or suppressing short-circuit between the first electrode and the hole transport layer.
This makes it possible to provide a solid type dye-sensitized photoelectric conversion element having an excellent photoelectric conversion efficiency.
In the present invention, it is preferred that the short-circuit preventing means includes a barrier layer having a porosity smaller than the porosity of the electron transport layer. This makes it possible to more reliably prevent or suppress short-circuiting caused by electrical contact or the like between the first electrode and the hole transport layer, thereby enabling to effectively prevent the photoelectric conversion efficiency of the photoelectrical conversion element from being lowered.
In this case, it is preferred that when the porosity of the barrier layer is defined by A% and the porosity of the electron transport layer is defined by B%, the value of B/A is equal to or greater than 1.1. This makes it possible for the barrier layer and the electron transport layer to exhibit respective functions more appropriately.
More preferably, the porosity of the barrier layer is set to be equal to or less than 20%. This makes it possible to prevent or suppress the short-circuiting between the first electrode and the hole transport layer more reliably.
Further, it is preferred that the ratio of the thickness of the barrier layer with respect to the thickness of the electron transport layer is in the range of 1:99 to 60:40. This also makes it possible to prevent or suppress the short-circuiting between the first electrode and the hole transport layer more reliably. Further, it is also possible to effectively prevent the amount of light to be reached to the dye layer from being reduced.
Furthermore, it is also preferred that the average thickness of the barrier layer is in the range of 0.01 to 10 &mgr;m. This also makes it possible to effectively prevent the amount of light to be reached to the dye layer from being reduced.
Moreover, it is also preferred that the barrier layer has electric conductivity which is substantially the same as that of the electron transport layer. This makes it possible to effectively move electrons from the electron transport layer to the barrier layer.
Moreover, it is also preferred that the barrier layer is mainly constituted from titanium oxide. This also makes it possible to effectively move electrons from the electron transport layer to the barrier layer.
Moreover, it is also preferred that the barrier layer is formed by means of a MOD method including a metal organic deposition and a metal organic decomposition. This makes it possible to easily and reliably obtain a barrier layer having a dense structure, that is having a desired porosity.
In this case, preferably the barrier layer is formed using a barrier layer material when the barrier layer is formed by means of the MOD method, in which the barrier layer material contains a metal alkoxide and an additive having a function for stabilizing the metal alkoxide.
Further, preferably, the additive is a hydrolysis suppressing agent that suppresses hydrolysis of the metal alkoxide by being replaced with alkoxyl group of the metal alkoxide and coordinated with the metallic atoms of the metal alkoxide.
Further, it is also preferred that the resistance value in the thickness direction of the total of the barrier layer and the electron transport layer is equal to or greater than 100 k&OHgr;/cm
2
. This makes it possible to prevent or suppress the short-circuiting between the first electrode and the hole transport layer more reliably.
Furthermore, it is also preferred that the barrier layer is disposed between the barrier layer and the electron transport layer. This also makes it possible to prevent or suppress the short-circuiting between the first electrode and the hole transport layer even more reliably.
In this case, it is preferred that the boundary between the barrier layer and the electron transport layer is unclear. This makes it possible to reliably move electrons between the electron transport layer and the barrier layer.
It is also preferred that the barrier layer and the electron transport layer are integrally formed with each other. This also makes it possible to reliably move electrons between the electron transport layer and the barrier layer.
Further, it is also preferred that a part of the electron transport layer functions as the barrier layer. This also makes it possible to reliably move electrons between the electron transport layer and the barrier layer.
In the present invention, it is preferred that the short-circuit preventing means is a spacer which defines a space between the fist electrode and the hole transport layer. This makes it possible to more reliably prevent or suppress short-circuiting caused by electrical contact or the like between the first electrode and the hole transport layer, thereby enabling to effectively prevent the photoelectric conversion efficiency of the photoelectrical conversion element from being lowered.
In this case, it is preferred that when the average thickness of the spacer is defined by H &mgr;m, the maximum thickness of the hole transport layer is defined
Fujimori Yuji
Miyamoto Tsutomu
Diamond Alan
Seiko Epson Corporation
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