JP2001274430A - Thin film photoelectric converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film photoelectric converter capable of preventing conversion efficiency from being lowered. SOLUTION: A thin film photoelectric converter 1 is provided with a glass substrate 11, a noncrystalline photoelectric converting unit 13 formed on the glass substrate 11 and provided with a photoelectric converting layer practically composed of a noncrystalline silicon, a transparent conductive layer 21, which is formed on the noncrystalline photoelectric converting unit 13 having the resistivity of >=1×10-4 Ωcm and <=1×10-2 Ωcm, and a polycrystal photoelectric converting unit 14 formed on the transparent conductive layer 21 and provided with a photoelectric converting layer practically composed of a polycrystal silicon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film photoelectric conversion device, and more particularly to a so-called tandem thin film photoelectric conversion device comprising an amorphous photoelectric conversion unit and a polycrystalline photoelectric conversion unit. is there.

[0002]

2. Description of the Related Art In recent years, as a thin-film photoelectric material constituting a thin-film photoelectric conversion device, a thin-film photoelectric material made of amorphous silicon which can be manufactured at relatively low cost,
Thin-film photoelectric materials made of polycrystalline silicon are known.
A thin-film photoelectric material made of amorphous silicon has a wavelength of 350
It absorbs light of a relatively short wavelength of ８００800 nm. A thin-film photoelectric material made of polycrystalline silicon has a wavelength of 700 to 110.
It absorbs light with a relatively long wavelength of 0 nm. A so-called tandem type that can realize high conversion efficiency by laminating a thin-film photoelectric material made of amorphous silicon and a thin-film photoelectric material made of polycrystalline silicon and absorbing both long-wavelength light and short-wavelength light. Thin film photoelectric conversion devices have been developed.

The structure of a conventional tandem thin film photoelectric conversion device will be described below. FIG. 4 is a cross-sectional view of a conventional tandem thin film photoelectric conversion device. Referring to FIG. 4, a tandem-type thin-film photoelectric conversion device 101 includes a glass substrate 111.
, Transparent conductive layer 112, and amorphous photoelectric conversion unit 1
13, a polycrystalline photoelectric conversion unit 114, an oxide layer 116, and a back electrode 115. Glass substrate 11
The transparent conductive layer 112 is formed so as to be in contact with 1. An amorphous photoelectric conversion unit 113 is formed so as to be in contact with transparent conductive layer 112. A polycrystalline photoelectric conversion unit 114 is formed so as to be in contact with the amorphous photoelectric conversion unit 113. An oxide layer 116 is formed so as to be in contact with polycrystalline photoelectric conversion unit 114. Back electrode 115 is brought into contact with oxide layer 116.
Are formed.

[0004] Glass substrate 111 and transparent conductive layer 112
Has a low light absorption coefficient and transmits most of the light. The amorphous photoelectric conversion unit 113 includes a p-type amorphous silicon layer 113p doped with a p-type impurity and an i-type amorphous silicon layer as a photoelectric conversion layer formed of an intrinsic semiconductor not doped with an impurity. It is composed of a silicon layer 113i and an n-type amorphous silicon layer 113n doped with an n-type impurity.

The p-type amorphous silicon layer 113p is formed so as to be in contact with the transparent conductive layer 112. The i-type amorphous silicon layer 113i is formed to be in contact with the p-type amorphous silicon layer 113p. n-type amorphous silicon layer 11
3n is formed in contact with the i-type amorphous silicon layer 113i.

The polycrystalline photoelectric conversion unit 114 has a p-type polycrystalline silicon layer 114 p doped with a p-type impurity.
And an i-type polycrystalline silicon layer 114 as a photoelectric conversion layer composed of an intrinsic semiconductor not doped with an impurity
i and an n-type polycrystalline silicon layer 114n doped with an n-type impurity.

The p-type polycrystalline silicon layer 114p is formed so as to be in contact with the n-type amorphous silicon layer 113n. i
Type polycrystalline silicon layer 114i is formed to be in contact with p-type polycrystalline silicon layer 114p. The n-type polycrystalline silicon layer 114n is formed so as to be in contact with the i-type polycrystalline silicon layer 114i. An oxide layer 116 made of zinc oxide (ZnO) is formed on n-type polycrystalline silicon layer 114n. Back electrode 11 made of silver on oxide layer 116
5 are formed.

A hole 112a is formed in the transparent conductive layer 112. The amorphous photoelectric conversion unit 113 is connected to the glass substrate 111 via the hole 112a. Amorphous photoelectric conversion unit 113 and polycrystalline photoelectric conversion unit 1
Holes 117 are formed in 14 and oxide layer 116.
The hole 117 is filled with the back electrode 115. Amorphous photoelectric conversion unit 113 and polycrystalline photoelectric conversion unit 1
A hole 118 is formed so as to separate 14 from back electrode 115.

A plurality of such thin-film photoelectric conversion devices 101 constitute a so-called solar cell.

FIG. 5 is a sectional view showing a method of manufacturing the thin-film photoelectric conversion device shown in FIG. Referring to FIG. 5, when manufacturing a thin film photoelectric conversion device, first, a glass substrate 111 is formed.
A transparent conductive layer 112 is formed thereon. A hole 112a is formed in the transparent conductive layer 112. The p-type amorphous silicon layer 11 is formed on the transparent conductive layer 112 by a CVD method (chemical vapor deposition).
An amorphous photoelectric conversion unit 113 including the 3p, i-type amorphous silicon layer 113i and the n-type amorphous silicon layer 113n is formed. A polycrystalline photoelectric conversion unit 114 including a p-type polycrystalline silicon layer 114p, an i-type polycrystalline silicon layer 114i, and an n-type polycrystalline silicon layer 114n is formed on the amorphous photoelectric conversion unit 113 by a CVD method. A hole 117 is formed in the amorphous photoelectric conversion unit 113 and the polycrystalline photoelectric conversion unit 114. An oxide layer 116 is formed on the polycrystalline photoelectric conversion unit 114 by sputtering, and then the back electrode 1 made of silver is formed.
15 are formed. An amorphous photoelectric conversion unit 113,
Polycrystalline photoelectric conversion unit 114 and oxide layer 116
And a second harmonic laser of YAG (yttrium-aluminum-garnet) is incident from the direction indicated by arrow 121 to cut off the back electrode 115. This allows
A hole 118 is formed by removing the portions of the amorphous photoelectric conversion unit 113 and the polycrystalline photoelectric conversion unit 114 irradiated with the laser, and the portions of the oxide layer 116 and the back surface electrode 115 located thereon. . Thus, the thin-film photoelectric conversion device 101 shown in FIG. 4 is completed.

[0011]

FIG. 6 is a sectional view showing a problem that occurs in a conventional thin film photoelectric conversion device. Referring to FIG. 6, the amorphous photoelectric conversion unit 113 and the polycrystalline photoelectric conversion unit 1 according to the process shown in FIG.
14 is cut, the amorphous photoelectric conversion unit 1
13 and the polycrystalline photoelectric conversion unit 114 are irradiated with a laser. Since this laser has a large energy density, the amorphous photoelectric conversion unit 11 irradiated with the laser
The temperature of the third and polycrystalline photoelectric conversion units 114 and the vicinity thereof becomes high. At this time, the p-type polycrystalline silicon layer 1
The portion of the n-type amorphous silicon layer 113n that is in contact with 14p is crystallized using the polycrystalline silicon constituting the p-type polycrystalline silicon layer 114 as a nucleus. This crystallization allows the i-type amorphous silicon layer 113i and the p-type amorphous silicon layer 11
Spread to 3p. Thus, a polycrystalline layer 113d is formed at the end of the amorphous photoelectric conversion unit 113. When the polycrystalline layer 113d is formed, the impurities in the n-type amorphous silicon layer 113n and the p-type amorphous silicon layer 113p are diffused, so that the pn junction is broken. As a result, there is a problem that a leak current is generated via the polycrystalline layer 113d and the conversion efficiency is reduced.

Further, the p-type amorphous silicon layer 113p
And the n-type amorphous silicon layer 113n is short-circuited, so that the amorphous photoelectric conversion unit 113 made of amorphous silicon
However, there is a problem that power cannot be extracted from the battery and the conversion efficiency is reduced.

Accordingly, the present invention has been made to solve the above-described problems, and has as its object to provide a thin-film photoelectric conversion device capable of preventing a decrease in conversion efficiency. .

[0014]

The thin-film photoelectric conversion device according to the present invention includes a transparent insulating substrate, an amorphous photoelectric conversion unit, a transparent conductive layer, and a polycrystalline photoelectric conversion unit. The amorphous photoelectric conversion unit is formed on a transparent insulating substrate and includes a photoelectric conversion layer substantially made of amorphous silicon. Here, “substantially amorphous” means not only a completely amorphous body but also an amorphous body containing a small amount of polycrystal. The transparent conductive layer is formed on the amorphous photoelectric conversion unit and has a resistivity of 1 × 10 ⁻⁴ Ωcm.
It is 1 × 10 ⁻² Ωcm or less. The polycrystalline photoelectric conversion unit is formed on the transparent conductive layer and includes a photoelectric conversion layer substantially made of polycrystalline silicon. Here, “substantially polycrystal” means not only a complete polycrystal, but also
It also means a polycrystalline material containing a small amount of an amorphous material.

In the thin-film photoelectric conversion device thus configured, since the transparent conductive layer is interposed between the amorphous photoelectric conversion unit and the polycrystalline photoelectric conversion unit, amorphous silicon and polycrystalline There is no direct contact with silicon. Therefore, in the process of manufacturing a thin film photoelectric conversion device, even if the amorphous silicon is heated, the amorphous silicon does not contact the polycrystalline silicon acting as a seed crystal, and thus the crystallization of the amorphous silicon is suppressed. can do.
As a result, diffusion of impurities in the amorphous silicon can be suppressed, and no leak current or short circuit occurs at the end of the amorphous photoelectric conversion unit. Thereby, a decrease in conversion efficiency can be prevented.

The resistivity of the transparent conductive layer interposed between the amorphous photoelectric conversion unit and the polycrystalline photoelectric conversion unit is related to the light transmittance. That is, when the number of crystal defects in the transparent conductive layer increases, the number of carriers that carry charges in the transparent conductive layer increases, so that the resistivity decreases. At the same time, the light transmittance also decreases. When the number of crystal defects in the transparent conductive layer is small, the number of carriers is reduced, so that the resistivity increases. At the same time, the light transmittance also increases. The resistivity of the transparent conductive layer is 1 ×
By setting it to 10 ⁻⁴ Ωcm or more, the light transmittance of the transparent conductive layer can be increased. As a result, since the transparent conductive layer does not shield light, a decrease in conversion efficiency can be prevented. Further, the resistivity is set to 1 × 10 ⁻² Ωc.
By setting m or less, the electric resistance of the transparent conductive layer does not become too large. As a result, a decrease in conversion efficiency can be prevented.

Preferably, the transparent conductive layer has a refractive index different from that of the photoelectric conversion layer substantially made of amorphous silicon. The thickness of the amorphous photoelectric conversion unit is 0.1 μm or more and 0.2 μm or less. In this case, light transmitted through the transparent insulating substrate and incident on the amorphous photoelectric conversion unit reaches the interface between the amorphous photoelectric conversion unit and the transparent conductive layer. Since the refractive index of the photoelectric conversion layer made of amorphous silicon constituting the amorphous photoelectric conversion unit is different from the refractive index of the transparent conductive layer, part of the light is reflected by the transparent conductive layer and becomes amorphous again. Incident on the photoelectric conversion unit. When comparing amorphous silicon and polycrystalline silicon, amorphous silicon has lower conversion efficiency than polycrystalline silicon. Therefore, when the same amount of light is incident on the amorphous photoelectric conversion unit and the polycrystalline photoelectric conversion unit, the current density of the current generated in the amorphous photoelectric conversion unit becomes smaller than the current density generated in the polycrystalline photoelectric conversion unit. Is smaller than the current density. Therefore, the current density of the entire thin-film photoelectric conversion device is determined by the current density of the amorphous photoelectric conversion unit having low conversion efficiency. In the present invention, as described above, since a transparent conductive layer that reflects light is interposed between an amorphous photoelectric conversion unit and a polycrystalline photoelectric conversion unit, many amorphous photoelectric conversion units are used. Of light is incident. As a result, the current density of the current flowing through the amorphous photoelectric conversion unit increases, and the conversion efficiency of the entire thin-film photoelectric conversion device can be improved.

Preferably, the resistivity of the transparent conductive layer increases when heated. In this case, since the resistivity increases in the portion of the transparent conductive layer heated by the laser, it is possible to further prevent generation of a leak current in the heated portion. As a result, a decrease in conversion efficiency can be more effectively suppressed.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of a thin-film photoelectric conversion device according to Embodiment 1 of the present invention. Referring to FIG. 1, a thin-film photoelectric conversion device 1 according to Embodiment 1 of the present invention includes a glass substrate 11 and a transparent conductive layer 12.
And the amorphous photoelectric conversion unit 13 and the transparent conductive layer 21
And a polycrystalline photoelectric conversion unit 14 and a back electrode 15
And an oxide layer 16.

A transparent conductive layer 12 is formed on a glass substrate 11 as a transparent insulating substrate. On the transparent conductive layer 12, an amorphous photoelectric conversion unit 13 as a photoelectric conversion layer substantially made of amorphous silicon is formed. The transparent conductive layer 21 is formed on the amorphous photoelectric conversion unit 13. On the transparent conductive layer 21, a polycrystalline photoelectric conversion unit 14 as a photoelectric conversion layer substantially made of polycrystalline silicon is formed. An oxide layer 16 made of zinc oxide (ZnO) is formed on the polycrystalline photoelectric conversion unit 14.
The back electrode 15 made of silver is formed on the oxide layer 16.

The transparent conductive layer 12 has a high light transmittance and a high electrical conductivity, for example, zinc oxide (ZnO).
O), silicon dioxide (SiO ₂ ), tin oxide (Sn)
O ₂ ), indium oxide (InO ₂ ), aluminum oxide (Al ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), or titanium oxide (TiO ₂ ).

The amorphous photoelectric conversion unit 13 includes a p-type amorphous silicon layer 13p doped with a p-type impurity,
I-type amorphous silicon layer 13i as a photoelectric conversion layer substantially made of amorphous silicon composed of an intrinsic semiconductor not doped with impurities, and n-type amorphous silicon doped with n-type impurities And a layer 13n. The n-type amorphous silicon layer 13n contacts the transparent conductive layer 12. The i-type amorphous silicon layer 13i contacts the p-type amorphous silicon layer 13p. n-type amorphous silicon layer 13n
Contacts the i-type amorphous silicon layer 13i. The thickness of the amorphous photoelectric conversion unit 13 is 0.3 μm. The transparent conductive layer 21 is formed so as to be in contact with the n-type amorphous silicon layer 13n of the amorphous photoelectric conversion unit 13. The thickness of the transparent conductive layer 21 is 30 nm. The material forming the transparent conductive layer 21 is the same as the material forming the transparent conductive layer 12, that is, zinc oxide (ZnO), silicon dioxide (SiO ₂ ), tin oxide (SnO ₂ ), indium oxide (I
nO ₂ ), aluminum oxide (Al ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), or titanium oxide (TiO ₂ ). Note that these substances have crystal defects due to lack of oxygen atoms. The refractive index of the oxide constituting the transparent conductive layer 21 with respect to visible light is about 1.6.

The polycrystalline photoelectric conversion unit 14 is formed so as to be in contact with the transparent conductive layer 21. The polycrystalline photoelectric conversion unit 14 includes a p-type polycrystalline silicon layer 14p doped with a p-type impurity and a photoelectric conversion substantially composed of polycrystalline silicon formed of an undoped intrinsic semiconductor. It is composed of an i-type polycrystalline silicon layer 14i as a layer and an n-type polycrystalline silicon layer 14n doped with an n-type impurity. The p-type polycrystalline silicon layer 14p contacts the transparent conductive layer 21. i-type polysilicon layer 14i contacts p-type polysilicon layer 14p. N-type polysilicon layer 14n contacts i-type polysilicon layer 14i. Polycrystalline photoelectric conversion unit 1
4 has a thickness of 1.5 μm. The amorphous silicon and the polycrystalline silicon constituting the amorphous photoelectric conversion unit 13 and the polycrystalline photoelectric conversion unit 14 have a refractive index for visible light of about 3.3.

A hole 12a is formed in the transparent conductive layer 12. The amorphous photoelectric conversion unit 13 is connected to the glass substrate 11 through the hole 12a. Holes 17 are formed in the amorphous photoelectric conversion unit 13, the polycrystalline photoelectric conversion unit 14, and the oxide layer 16. Hole 17 is connected to back electrode 1
5 are filled. An amorphous photoelectric conversion unit 13;
A hole 18 is formed so as to separate the polycrystalline photoelectric conversion unit 14, the oxide layer 16, and the back electrode 15. A plurality of such thin film photoelectric conversion devices 1 are formed on the glass substrate 11 and the transparent conductive layer 12.

Next, a method of manufacturing the thin-film photoelectric conversion device shown in FIG. 1 will be described. FIG. 2 is a cross-sectional view showing a manufacturing process of the thin-film photoelectric conversion device shown in FIG. Referring to FIG. 2, a thickness of 3 is formed on glass substrate 11 by sputtering.
A 0 nm transparent conductive layer 12 is formed. Hole 1 in transparent conductive layer
2a is formed. An amorphous photoelectric conversion unit 13 including a p-type amorphous silicon layer 13p, an i-type amorphous silicon layer 13i, and an n-type amorphous silicon layer 13n is formed on the transparent conductive layer 12 by a plasma CVD method. A transparent conductive layer 21 made of zinc oxide is formed on the amorphous photoelectric conversion unit 13 by sputtering. P-type polycrystalline silicon layer 14 on transparent conductive layer 21 by plasma CVD
The polycrystalline photoelectric conversion unit 14 including the p, i-type polycrystalline silicon layer 14i and the n-type polycrystalline silicon layer 14n is formed. An oxide layer 16 is formed on the polycrystalline photoelectric conversion unit 14 by sputtering. Apertures 17 are formed by irradiating the amorphous photoelectric conversion unit 13 and the polycrystalline photoelectric conversion unit 14 with laser. The back electrode 15 is formed on the oxide layer 16 by sputtering. Amorphous photoelectric conversion unit 13 and polycrystalline photoelectric conversion unit 14
In order to remove the oxide layer 16 and a part of the back electrode 15, the second harmonic pulse laser of YAG is irradiated from the direction indicated by the arrow 31. At this time, the laser power is 0.4
W, the focus of the laser was set at a position 3 mm away from the interface between the n-type polycrystalline silicon layer 14n and the oxide layer 16 toward the oxide layer. Manufacturing under such a focus condition is referred to as a defocus amount of 3 mm. Thereby, the amorphous photoelectric conversion unit 13 and the polycrystalline photoelectric conversion unit 1
4, a part of the oxide layer 16, and a part of the back electrode 15, whereby the thin-film photoelectric conversion device 1 can be formed.

According to such a process, the plane area is 1 cm ×
A plurality of thin-film photoelectric conversion devices 1 as 1 cm solar cells were formed. As a comparative example, a thin film photoelectric conversion device similar to the thin film photoelectric conversion device 1 shown in FIG. 1 except that the transparent conductive layer 21 was not included was formed. The performance of each of the thin-film photoelectric conversion device 1 according to the present invention and the thin-film photoelectric conversion device according to the comparative example was compared. In the thin-film photoelectric conversion device 1 according to the present invention, the open-circuit voltage is 1.35 V,
The short-circuit current was 12.1 mA, the form factor was 73.5%, and the conversion efficiency was 12.0%. On the other hand, in the thin-film photoelectric conversion device 1 according to the comparative example, the open-circuit voltage is 1.35 V, the short-circuit current is 11.5 mA, the form factor is 68%, and the conversion efficiency is 10.
6%. Therefore, in the thin-film photoelectric conversion device 1 according to the present invention, since the form factor FF and the short-circuit current were improved, the conversion efficiency was higher than that of the comparative example.

The reason why the conversion efficiency of the product of the present invention is higher than that of the comparative example is considered to be as follows. That is, the amorphous photoelectric conversion unit 13 is not in direct contact with the polycrystalline photoelectric conversion unit 14 made of polycrystalline silicon. Therefore, even when the amorphous-type photoelectric conversion unit 13 made of amorphous is heated, since there is no seed crystal for crystallization, it is possible to prevent amorphous silicon from being polycrystallized. As a result, diffusion of the p-type impurity and the n-type impurity in the amorphous photoelectric conversion unit 13 can be prevented, and a decrease in conversion efficiency can be suppressed.

Further, the light transmitted through the glass substrate 11 and the transparent conductive layer 12 and incident on the amorphous type photoelectric conversion unit 13 made of amorphous silicon is converted into the amorphous type photoelectric conversion unit 13 and the transparent conductive layer 21. Reach the interface. The refractive index (about 3.3) of the amorphous photoelectric conversion unit 13 made of amorphous silicon is the same as the refractive index (about 1.6) of the transparent conductive layer 21.
Therefore, light is reflected by the transparent conductive layer 21 and again enters the amorphous photoelectric conversion unit 13, so that a large amount of light enters the amorphous photoelectric conversion unit 13.
As a result, the current density of the current flowing through the amorphous photoelectric conversion unit 13 increases, and the conversion efficiency of the thin-film photoelectric conversion device 1 can be improved.

(Embodiment 2) In Embodiment 2, FIG.
When the thin-film photoelectric conversion device 1 indicated by is manufactured, the thin-film photoelectric conversion device was manufactured by changing the amount of defocus during laser scribing in various ways. Further, as shown in the comparative example of the first embodiment, thin film photoelectric conversion devices not including the transparent conductive layer 21 were formed with various defocus amounts. For these thin film photoelectric conversion devices, it was determined how much the shape factor FF was reduced with respect to the shape factor of the thin film photoelectric conversion device in which the holes 18 were formed by chemical etching without irradiating laser. The result is shown in FIG.

In FIG. 3, a solid line 201 is data indicating the relationship between the defocus amount and the reduction rate of the form factor FF in the thin-film photoelectric conversion device according to the present invention having the transparent conductive layer 21. A solid line 202 is data indicating the relationship between the defocus amount and the reduction rate of the shape factor FF for the thin-film photoelectric conversion device according to the comparative example having no transparent conductive layer 21. From FIG. 3, in the thin-film photoelectric conversion device 1 according to the present invention, when the defocus amount is increased, the annealing area increases, so that the shape factor FF decreases. However, the decrease rate is smaller than that of the thin-film photoelectric conversion device according to the comparative example. It can be seen that it has become smaller.

Embodiment 3 In Embodiment 3, a plurality of films made of tin oxide (SnO ₂ ) used as the transparent conductive layer 21 were prepared. Each film was heated at 25 ° C, 100
Annealing was performed at 200C, 200C, 300C, and 400C for 1 hour to form Samples 1 to 5. For each sample after annealing, the sheet resistance and wavelength were 55
The transmittance of 0 nm light was examined. Table 1 shows the results.

[0033]

[Table 1]

According to Table 1, the sheet resistance of Sample 4 annealed at 300 ° C. was 300Ω. This is presumably because the annealing promoted oxidation sufficiently, reduced oxygen vacancies and lowered the carrier concentration. In Sample 4, although the crystallinity was also improved and the mobility of the carrier was increased, the resistivity was increased as a result of the remarkable decrease in the carrier concentration.

By using a material whose resistivity increases when heated as described above as the transparent conductive layer 21, the resistance of the annealed portion is increased. As a result, current does not leak in the annealed portion, and a decrease in conversion efficiency can be prevented.

(Embodiment 4) In Embodiment 4, FIG.
The thickness of the amorphous-type photoelectric conversion unit 13 made of amorphous silicon is represented by 0.1 μm, 0.15 μm, 0.2 μm.
m, 0.3 μm and 0.4 μm, and the transparent conductive layer 21
Thin film photoelectric conversion device without sample (samples 11 to 15)
Was formed as a comparative product. The thickness of the amorphous photoelectric conversion unit 13 made of amorphous silicon shown in FIG. 1 is 0.1 μm, 0.15 μm, 0.2 μm, 0.3 μm and 0.4 μm, and the transparent photoelectric conversion unit 13 is 15 nm thick. Conductive layer 21
-Film photoelectric conversion device 1 having sample (samples 16 to 20)
Was formed as the product of the present invention. The current density generated when each of the samples 11 to 20 was irradiated with light was examined. Table 2 shows the results.

[0037]

[Table 2]

As can be seen from Table 2, in the samples 16 to 20 in which the transparent conductive layer 21 was formed, the amorphous type photoelectric conversion unit 13 was larger than the samples 11 to 15 in which the transparent conductive layer 21 was not formed, even if the film thickness thereof was thin. It was found that a current density was obtained. It is considered that this is mainly due to light reflection. That is, as described above, the glass substrate 1
1 and the light incident on the amorphous photoelectric conversion unit 13 via the transparent conductive layer 12 are reflected at the interface between the transparent conductive layer 21 and the amorphous photoelectric conversion unit 13 and are reflected on the amorphous photoelectric conversion unit 13. 13 becomes easy to be confined. As a result, the amorphous photoelectric conversion unit 13 is irradiated with a large amount of light, the current density of the current generated in the photoelectric conversion layer increases, and the current density of the entire thin-film photoelectric conversion device 1 increases. .

In the case of manufacturing a tandem type thin film photoelectric conversion device, from the viewpoint of productivity (film formation speed) and reliability (film peeling due to an increase in film thickness), a polycrystalline type photoelectric conversion device made of polycrystalline silicon is used. It is desirable that the thickness of the conversion unit 14 be 2 to 3 μm. Also, the amorphous photoelectric conversion unit 1
3 and the current density of the polycrystalline photoelectric conversion unit 14 must be matched. Considering such circumstances, the current density of the current generated in the polycrystalline photoelectric conversion unit 14 is 1
It is considered to be 0 to 11 mA / cm ² . Therefore, in the present invention product in which the transparent conductive layer 21 is formed, the upper limit of the thickness of the amorphous photoelectric conversion unit 13 made of amorphous silicon is preferably 0.2 μm. The lower limit is 0.1
It is preferably set to μm.

Embodiment 5 In Embodiment 5, the relationship between the resistivity of the transparent conductive layer 21 and the conversion efficiency of the thin-film photoelectric conversion device was examined. The amorphous conductive type photoelectric conversion unit 13 has a thickness of 0.15 μm, the polycrystalline type photoelectric conversion unit 14 has a thickness of 2 μm, and the transparent conductive layer 2 has a structure shown in FIG.
The resistivity of 1 is 3 × 10 ⁻⁵ Ωcm, 1 × 10 ⁻⁴ Ωcm, 2
× 10 ⁻³ Ωcm, 1 × 10 ⁻² Ωcm and 3 × 10 ⁻¹ Ω
cm thin film photoelectric converter (samples 21 to 2
5) was formed. For each of the samples 21 to 25, the open-end voltage, the short-circuit current, the form factor FF, and the conversion efficiency were examined. Table 3 shows the results.

[0041]

[Table 3]

As shown in Table 3, the resistivity of the transparent conductive layer was 1 × 10
If it is less than ^-4 Ωcm, the short-circuit current becomes small, so that the conversion efficiency decreases. If the resistivity exceeds 1 × 10 ^-2 Ωcm, the conversion factor decreases because the shape factor decreases. Therefore, the resistivity needs to be 1 × 10 ⁻⁴ Ωcm or more and 1 × 10 ⁻² Ωcm or less.

Although the embodiment of the present invention has been described above, the embodiment shown here can be variously modified.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0045]

According to the present invention, it is possible to prevent the occurrence of a leak current at the end of an amorphous photoelectric conversion unit including a photoelectric conversion layer substantially composed of amorphous silicon, thereby lowering the conversion efficiency. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a thin-film photoelectric conversion device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of the thin-film photoelectric conversion device shown in FIG.

FIG. 3 is a graph showing a relationship between a defocus amount and a change amount of a shape factor in a thin film photoelectric conversion device according to the present invention and a thin film photoelectric conversion device according to a comparative example.

FIG. 4 is a cross-sectional view of a conventional tandem-type thin-film photoelectric conversion device.

5 is a cross-sectional view illustrating a method for manufacturing the thin-film photoelectric conversion device shown in FIG.

FIG. 6 is a cross-sectional view showing a problem that occurs in a conventional thin-film photoelectric conversion device.

[Explanation of symbols]

Reference Signs List 1 thin film photoelectric conversion device, 11 glass substrate, 13 amorphous type photoelectric conversion unit, 13ii type amorphous silicon layer, 14 polycrystalline type photoelectric conversion unit, 14ii type polycrystalline silicon layer, 21 transparent conductive layer.

Claims (3)

[Claims] 1. An amorphous photoelectric conversion unit including a transparent insulating substrate, a photoelectric conversion layer substantially formed of amorphous silicon, and formed on the transparent insulating substrate; A transparent conductive layer having a resistivity of 1 × 10 ⁻⁴ Ωcm or more and 1 × 10 ⁻² Ωcm or less, formed on the conversion unit; and substantially polycrystalline silicon formed on the transparent conductive layer. And a polycrystalline photoelectric conversion unit including a photoelectric conversion layer. 2. The transparent conductive layer has a refractive index different from that of the photoelectric conversion layer substantially made of amorphous silicon, and the thickness of the amorphous photoelectric conversion unit is 0.1 μm or more. The thin-film photoelectric conversion device according to claim 1, wherein the thickness is 2 μm or less. 3. The thin-film photoelectric conversion device according to claim 1, wherein the resistivity of the transparent conductive layer increases when heated.