JP2661286B2 - Photoelectric conversion device - Google Patents

Description

The present invention relates to a photoelectric conversion device that converts light energy such as sunlight into electric energy by using a pn or pin junction of a semiconductor. About.

[Conventional technology]

A conventional photoelectric conversion device such as a solar cell has a structure in which a p-layer and an n-layer or a p-layer, an i-layer, and an n-layer amorphous semiconductor layer are stacked on a substrate, or a single-crystal silicon plate or a polycrystalline silicon plate. It is known to use a pn junction or a pin junction formed by forming a p-layer and an n-layer by doping the elements of group III and group V of the periodic table from different surfaces.

[Problems to be solved by the invention]

In a conventional photoelectric conversion device, light incident from one of stacked amorphous semiconductor layers or from one surface of a single crystal or polycrystalline silicon plate is doped with impurities to a junction having a photoelectric conversion function. The light must pass through the p-layer or the n-layer, and the light absorbed by these doping layers cannot be used effectively, and the photoelectric conversion efficiency is not improved. On the other hand, there is a method in which a fine array of a p region and an n region is formed on a crystalline silicon plate, these are wired, and light is incident on these. However, for this purpose, it is necessary to repeat the photo process and the doping process in a multiplex manner, resulting in a problem that the cost is extremely high.

An object of the present invention is to solve the above-described problems and to provide a low-cost photoelectric conversion device which has high photoelectric conversion efficiency by reaching a junction without light passing through a doped layer.

[Means for solving the problem]

In order to achieve the above object, in the photoelectric conversion device of the present invention, at least a part of the surface is dispersed and buried in the intrinsic semiconductor layer with the first conductive type semiconductor layer. In addition, a second electrode is attached to one surface of the intrinsic semiconductor layer via a semiconductor layer of a second conductivity type.

[Action]

A pin junction is formed by the first conductivity type layer, the intrinsic semiconductor layer, and the second conductivity type layer. When light enters from the side of the intrinsic semiconductor layer where the second electrode is not provided, the light reaches the i-layer which is the photoelectric conversion layer without passing through the doping layer, and is not absorbed in the doping layer. Therefore, the photoelectric conversion efficiency is improved. The electromotive force generated by the incidence of light can be extracted from the first electrode and the second electrode.

〔Example〕

FIG. 1 shows a solar cell according to one embodiment of the present invention. A fiber electrode 1 made of metal or other conductive material and having a cross-sectional diameter of 1 μm or 100 μm and formed in a mesh shape or an interdigital shape is formed by plasma CVD, photo CVD or thermal CVD, for example, with a thickness of 120 mm. Is covered with the p-type amorphous silicon layer 2. Amorphous silicon carbide may be used instead of amorphous silicon. An undoped intrinsic or substantially intrinsic amorphous silicon layer 3 is formed thereon. As the film thickness of the intrinsic amorphous silicon layer 3 around each fiber electrode 1 increases, the adjacent layers adhere to each other to form an integrated film. On one surface of the filmed intrinsic amorphous silicon layer 3, an n-type amorphous silicon layer 4 having a thickness of, for example, 150 ° and a metal layer electrode 5 thereon are deposited, and on the other surface, silicon nitride is formed. A passivation film 6 made of Thereby, a solar cell using the fiber electrode 1 as a positive electrode and the layered electrode as a negative electrode is completed. The interval between the fiber electrodes 1 of this solar cell is variable as necessary,
The thickness is not more than twice the thickness of the intrinsic amorphous silicon layer 3 necessary for forming an i-n junction. The thickness of such an intrinsic amorphous layer increases as the lifetime increases.

FIG. 2 shows characteristics of such a solar cell with the thickness of the fiber electrode 1 as a parameter and characteristics of a conventional amorphous silicon solar cell in which p, i, n amorphous silicon layers are laminated on a glass substrate. And The fiber electrode 1 was made of molybdenum, and the interval between the electrodes was about twice the thickness of the fiber. The intrinsic layer 3 was made of amorphous silicon having a long lifetime and an optical band gap E _g = 1.65 eV, which was formed by thermal CVD, and its film thickness was about twice the thickness of the fiber. As can be seen from the figure, a significant improvement in the short-circuit current was observed, and as a result, the thickness of the fiber electrode was 4
In the case of μm, a conversion efficiency of 15% is obtained.

FIG. 3 shows a solar cell according to another embodiment of the present invention.
The difference from the solar cell shown in the figure is that the fiber electrode 1 is not used, the metal porous flat electrode 11 is used, and one surface of this electrode is passivated with a silicon nitride film 61 to reduce the interface area between the p layer 2 and the i layer 3. It is a point that has been reduced. Since the p / i interface area is reduced, the dark current is reduced and the open-circuit voltage is improved.

Although the amorphous silicon layer is used as the intrinsic layer in the above embodiment, the same effect can be obtained by using a polycrystalline silicon layer formed by thermal CVD. Further, the p layer and the n layer can be exchanged. However, since the diffusion length of holes is generally about one digit lower than the diffusion length of electrons, it is preferable to have a p-layer at the center of the intrinsic layer in the thickness direction.

〔The invention's effect〕

According to the present invention, the second conductivity type doping layer is not provided on the light incidence side of the intrinsic semiconductor layer surrounding the first electrode with the first conductivity type layer interposed therebetween, and the second conductivity type provided on the anti-light incidence side is not provided. By directly injecting light into the i-layer of the pin junction formed by the above-mentioned layers, the short-circuit current can be greatly improved, high conversion efficiency can be obtained, and a complicated photo process can be achieved. Is not required, so that an inexpensive photoelectric conversion device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a solar cell according to one embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the characteristics of the solar cell of FIG. FIG. 3 is a partial sectional view of a solar cell according to another embodiment of the present invention. 1: fiber electrode, 2: p-type amorphous silicon layer, 3: intrinsic amorphous silicon layer, 4: n-type amorphous silicon layer, 5: layered electrode, 11: porous flat electrode.

Claims (1)

(57) [Claims] A first electrode having at least a part of a surface covered with a semiconductor layer of a first conductivity type is dispersed and buried in an intrinsic semiconductor layer, and a second electrode is formed on one surface of the intrinsic semiconductor layer. A photoelectric conversion device, wherein a second electrode is attached via a conductive semiconductor layer.