JP3229705B2 - Photovoltaic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device,
In particular, the present invention relates to a so-called inverted type photovoltaic device in which a transparent electrode on the light incident side is formed on a semiconductor layer.

[0002]

2. Description of the Related Art In a reverse type structure of this type, as a means for improving output current, a transparent conductive film is inserted into an interface between a back electrode using a highly reflective metal and a semiconductor layer, and a semiconductor-metal interface is used. Is a structure that prevents the reflectance of
No. 41878.

[0003]

However, when a semiconductor layer is formed, a strongly reducing atmosphere such as a plasma containing a large amount of hydrogen is often used. When an oxide film is formed, the formation method is limited to an evaporation method, a sputtering method, or the like in order to avoid a reaction with a base metal, and a conductive metal oxide film having excellent resistance to a reducing atmosphere is formed. Was difficult.

[0004] Further, since a conductive metal oxide film having excellent resistance to a reducing atmosphere has poor conductivity, when it is used, the series resistance (Rs) of the photovoltaic device increases and the conversion efficiency (η) increases. ) Is caused. Further, the cost is increased due to the increase in the number of processes. Therefore, a main object of the present invention is to provide a low-cost and high-efficiency photovoltaic device that suppresses a decrease in light transmittance of a conductive metal oxide film even when exposed to a reducing atmosphere. That is.

[0005]

According to a first aspect of the present invention, there is provided a photovoltaic device having a semiconductor layer formed on a substrate covered with a conductive metal oxide film and a light incident side transparent electrode formed on the semiconductor layer. In the device, in which the conductive metal oxide film is used as one electrode or a part thereof, a region adjacent to the semiconductor layer in a thickness direction of the conductive metal oxide layer existing between the substrate and the semiconductor layer The first oxygen concentration of the other region is higher than the second oxygen concentration of the other region, and the first region is adjacent to the semiconductor layer.
The thickness of the conductive metal oxide layer in the region
A photovoltaic device characterized by having a range of 00 ° .

[0006]

[0007]

By making the oxygen concentration near the surface of the conductive metal oxide film that may be exposed to a reducing atmosphere, etc., higher than the main part of the other conductive metal oxide films, The resistance is increased, and a decrease in light transmittance in the conductive metal oxide film is suppressed. Further, since the oxygen concentration only near the surface is increased, the series resistance of the photovoltaic device hardly increases.

[0008] The effect of this, it is possible to improve the output current of the photovoltaic device. Further, since the conductive oxide film can be manufactured in one process, the cost can be reduced as compared with the case where the conductive oxide film is coated with another material.

[0009]

According to the present invention, a low-cost and high-efficiency photovoltaic device can be obtained. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A photovoltaic device 10 according to an embodiment shown in FIG. 1 includes an insulating plastic substrate 12, and is formed on the insulating plastic substrate 12 by a known RF sputtering method under the conditions shown in Table 1. , Ag and ITO respectively
, A highly reflective metal electrode layer 14 and a conductive metal oxide layer 16 were formed. The conductive metal oxide layer 16 comprises the first 9
50 ° (hereinafter, referred to as first conductive metal oxide layer 16a)
Was formed in an atmosphere containing only Ar, and then 50 ° (hereinafter, referred to as a second conductive metal oxide layer 16b) was formed by adding O ₂ to Ar.

On this, an amorphous semiconductor layer 18 is formed under the conditions shown in Table 2 in the order of an n-layer, an i-layer, and a p-layer by a known plasma C method.
It was formed by the VD method. Thereafter, ITO was formed as the light incident side translucent electrode layer 20 by RF sputtering under the conditions shown in Table 1. Further, the current collecting metal layer 22
A comb-shaped Ag electrode was formed by a known resistance heating evaporation method.

[0012]

[Table 1]

[0013]

[Table 2]

For comparison, the conductive metal oxide layer 16 is formed under the same conditions as those of the first conductive metal oxide layer 16a.
0 ° was formed, and the other conditions were all the same.

[0015]

[Table 3]

The first conductive metal oxide layer 16a has an oxygen concentration of 61% and the second conductive metal oxide layer 16b
Was 65% (107% of the oxygen concentration of the first conductive metal oxide layer 16a). At this time, the refractive index of the first conductive metal oxide layer 16a is 2.1, and the refractive index of the second conductive metal oxide layer 16b is 2.0 (the refractive index of the first conductive metal oxide layer 16a). 95% of the rate).

Next, FIG. 2 shows how the conversion efficiency of the photovoltaic device 10 changes when the thickness of the second conductive metal oxide layer 16b is changed in this embodiment. Referring to FIG. 2, the second conductive metal oxide layer 16b has a thickness of 10
The efficiency is improved in the range of Å to 100Å. this is,
In the region below 10 °, the efficiency is not improved because the resistance to the reducing atmosphere when forming the amorphous semiconductor layer 18 is not sufficient, and in the region above 100 °, the second conductive metal oxide layer 16b is formed. This is because the resistance component becomes large, causing a decrease in the fill factor, and as a result, the efficiency is reduced.

Further, the thickness of the second conductive metal oxide layer 16b is fixed at 50 ° and the first conductive metal oxide layer 16b is
FIG. 3 shows how the conversion efficiency of the photovoltaic device 10 changes when the ratio of the oxygen concentration of the second conductive metal oxide 16b to the oxygen concentration of a is changed. Note that the oxygen concentration of the second conductive metal oxide layer 16b was controlled by the oxygen partial pressure during formation.

The conversion efficiency is improved when the ratio of the oxygen concentration of the second conductive metal oxide layer 16b to the oxygen concentration of the first conductive metal oxide layer 16a is in the range of 105% to 110%. This is because the resistance to a reducing atmosphere when the amorphous semiconductor layer 18 is formed is not sufficient in the region of 105% or less, so that the efficiency is not improved. Since the resistance component of the material layer 16b is increased, the fill factor is reduced, and as a result, the efficiency is reduced.

The ratio of the oxygen concentration of the conductive metal oxide layer 16b to the oxygen concentration of the conductive metal oxide layer 16a is 105
% And 110% correspond to a refractive index of 96.5% and 93%, respectively. In the above embodiment, the sputtering method was used to form the conductive metal oxide layer. However, other methods, such as the thermal CVD method and the M
OCVD, EB vapor deposition, or the like may be used.

As the conductive metal oxide layer, tin oxide (SnO ₂ ) and indium tin oxide (IT
O), other conductive metal oxides such as zinc oxide (Zn)
Of course, O) or cadmium oxide (CdO) may be used.

[Brief description of the drawings]

FIG. 1 is a sectional structural view showing one embodiment of the present invention.

FIG. 2 is a graph showing a change in the conversion efficiency of the photovoltaic device when the thickness of the second conductive metal oxide layer is changed.

FIG. 3 is a graph showing a change in the conversion efficiency of the photovoltaic device when the ratio of the oxygen concentration of the second conductive metal oxide to the oxygen concentration of the first conductive metal oxide layer is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Photovoltaic device 12 ... Substrate 14 ... High reflective metal electrode 16a ... First conductive metal oxide layer 16b ... Second conductive metal oxide layer 18 ... Amorphous semiconductor layer 20 ... Light incident side transparent electrode

Continuation of the front page (56) References JP-A-5-13790 (JP, A) JP-A-1-205474 (JP, A) JP-A-58-80877 (JP, A) JP-A-59-119875 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (2)

(57) [Claims] 1. A photovoltaic device comprising: a semiconductor layer formed on a substrate covered with a conductive metal oxide film; and a light incident side transparent electrode formed on the semiconductor layer. In the case where the metal oxide film is used as one electrode or a part thereof, a first portion of a region adjacent to the semiconductor layer in a thickness direction of the conductive metal oxide layer existing between the substrate and the semiconductor layer Oxygen concentration higher than the second oxygen concentration in other areas
And the conductive metal acid in a region adjacent to the semiconductor layer
A photovoltaic device, wherein the thickness of the oxide layer is in the range of 10 to 100 degrees . 2. The photovoltaic device according to claim 1, wherein said first oxygen concentration is not less than 105% and not more than 110% with respect to said second oxygen concentration.