JP2958491B2 - Method for manufacturing photoelectric conversion device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a photoelectric conversion device such as a solar cell, and particularly relates to two impurity semiconductor layers (p-layer,
The present invention relates to a method for manufacturing a photoelectric conversion device including a non-single-crystal semiconductor in which an intrinsic semiconductor layer (i-layer) is provided between (n-layers).

[Prior Art] It is said that a photoelectric conversion device made of a non-single-crystal semiconductor has poor stability. Particularly, in the case of an amorphous silicon solar cell, there is a phenomenon called the Staebler-Wronski effect. In other words, the conductivity of the i-layer, which is the active layer, of the device consisting of the p-layer, the i-layer, and the n-layer gradually decreases due to the irradiation of light, the carrier transport ability decreases, and the conversion efficiency of the device decreases.

Therefore, attempts have been made to reduce the thickness of the i-layer to increase the electric field strength of this layer. By increasing the carrier transport ability in advance, it is intended to suppress the deterioration of the device.

In addition, attempts have been made to reduce the thickness of the i-layer of the element on the light-receiving surface side by tandem-connecting a plurality of elements each including a p-layer, an i-layer, and an n-layer. It is considered that the adoption of such a tandem structure suppresses deterioration of the light receiving surface side element due to the effect of thinning the i-layer, and suppresses deterioration of the back side element because only long wavelength light is irradiated. .

[Problems to be Solved by the Invention] Deterioration of the solar cell is not sufficiently suppressed even by adopting the i-layer thinning technology or the tandem structure, and the rate of deterioration of the photoelectric conversion efficiency when used outdoors for one year is 15%. There was a problem that exceeded.

It is considered that forming the i-layer between the p-layer and the n-layer at a high temperature is effective in suppressing deterioration. However, the present inventors have found that in the manufacturing process of the solar cell, only i
It has been found that the initial conversion efficiency is significantly reduced only by forming the layer at a high temperature. It is considered that when the i-layer is formed on the p-layer at a high temperature, impurities in the p-layer diffuse into the i-layer and an inactive layer is generated at the p / i interface, thereby lowering the initial conversion efficiency. .

The present invention relates to a photoelectric conversion device made of a non-single-crystal semiconductor in which an intrinsic semiconductor layer is provided between two impurity semiconductor layers having different conductivity types, and relates to a manufacturing method for preventing deterioration of initial conversion efficiency and preventing deterioration. The purpose is to provide.

[Means for Solving the Problems] The present invention provides a photoelectric conversion device including a non-single-crystal semiconductor in which an i-type intrinsic semiconductor layer is provided between two p-type and n-type impurity semiconductor layers having different conductivity types. The method of manufacturing
forming a p-layer or n-layer first impurity semiconductor layer;
After performing a heat treatment on this layer at a temperature equal to or higher than the film formation temperature of this layer, and forming an intrinsic semiconductor layer at a temperature equal to or higher than the film formation temperature of the first impurity semiconductor layer, forming a second impurity semiconductor layer of an n-layer or a p-layer; setting a heat treatment temperature of the first impurity semiconductor layer to 100 ° C. or more and 400 ° C. or less; Is set to 100 ° C. or more and 400 ° C. or less.

[Operation] According to the method of the present invention, the heat treatment and the plasma resistance of the first impurity semiconductor layer are improved by subjecting the formed first impurity semiconductor layer to heat treatment. Accordingly, the impurity does not diffuse into the first impurity semiconductor layer during the formation of the high-temperature i-layer. Therefore,
A decrease in the initial conversion efficiency can be prevented.

In addition, the high-temperature i-layer has a stable carrier transport ability even when irradiated with light, and the deterioration is suppressed.

Example FIG. 1 is a sectional view of a solar cell having an effective area of 1.0 cm ² (1.0 cm × 1.0 cm) manufactured by a method according to an example of the present invention. However, it is appropriate to use a parallel plate capacitively coupled glow discharge device for forming each semiconductor layer.

First, on a transparent electrode (2) made of, for example, SnO ₂ on a glass substrate (1), ap layer (3) made of a-SiC: H
Å Film formation. The gas flow rate supplied to the glow discharge device is Si
H ₄ is 5 sccm, CH ₄ is _{15sccm, B 2 H 6 (1000ppmH} 2 dilution product) is 1
5sccm, H ₂ is 50sccm. Other conditions are reaction pressure 1.0 To
rr, substrate temperature 200 ° C., RF power 50 mW / cm ² .

Next, heat treatment is performed on the p layer (3) in vacuum at 300 ° C. for 1 hour.

An i-layer (4) made of a-Si: H is formed at a temperature of 320 [deg.] C. on the p-layer (3) on which the heat treatment has been completed at 5000 [deg.] C. FIG.
Other film forming conditions are as follows: SiH ₄ gas flow rate 10 sccm, reaction pressure 0.3 T
orr, RF power 50 mW / cm ² .

Subsequently, an n-layer (5) made of microcrystallized a-Si: H is formed on the i-layer (4) by 300 [deg.]. The gas flow rate is 5 for SiH ₄
sccm, PH ₃ (1000ppmH ₂ dilution product) is 100 sccm, H ₂ is 200sccm
It is. Other conditions are: reaction pressure 1.0 Torr, substrate temperature 200
° C, RF power 500mW / cm ² .

Finally, a back electrode (6) made of metal is formed on the n-layer (5).

FIG. 2 is a graph showing initial external characteristics (current-voltage characteristics) of the solar cell manufactured by the method described above. For the measurement, AM-1, 100 mW / cm ² solar simulated light was used. Characteristic values are open circuit voltage 0.821volts, short circuit current 1
6.58 mA / cm ² , FF (fill factor) 61.11%, photoelectric conversion efficiency 8.328%. The rate of deterioration of the photoelectric conversion efficiency when used outdoors for one year is less than 10%, and the deterioration is greatly suppressed as compared with the related art.

FIG. 3 is a graph showing initial external characteristics of a comparative example. The solar cell according to this comparative example was produced in exactly the same manner as in the above example except that the heat treatment was not performed on the p-layer (3). That is, the heat treatment is not performed on the p-layer (3).
The i-layer (4) was formed at a high temperature of 0 ° C. The characteristic values of the comparative example measured under the same conditions as those of the example are 0.806 volts open circuit voltage, 15.58 mA / cm ² short circuit current, 47.82% FF, and 6.014% photoelectric conversion efficiency.

From the comparison between the two characteristics, it is understood that the initial external characteristics such as FF are improved by performing the heat treatment on the p layer (3) before forming the i layer (4) at a high temperature. In particular, a significant improvement in the initial conversion efficiency is observed.

The deposition temperature of the p-layer (3) is desirably 50 ° C. or more and 400 ° C. or less.

The heat treatment temperature of the p-layer (3) needs to be equal to or higher than the film formation temperature of the p-layer (3), and needs to be 100 ° C. or more and 400 ° C. or less. The optimum temperature is about 100 ° C. higher than the p-layer forming temperature. The processing time is preferably 10 minutes or more and 2 hours or less. Although the heat treatment is performed in a vacuum in this embodiment, the heat treatment may be performed in a hydrogen atmosphere or an inert gas atmosphere such as nitrogen.

The film formation temperature of the i-layer (4) also needs to be equal to or higher than the film formation temperature of the p-layer (3).
It is necessary that the temperature is not higher than 00 ° C. Among these, the range of 200 ° C. or more and 400 ° C. or less is desirable.

The film formation temperature of the n-layer (5) formed last in the semiconductor layer is suitably equal to the film formation temperature of the p-layer (3) or the same as the film formation temperature of the i-layer (4). The thicknesses of the p, i, and n layers (3, 4, 5) are not limited to the above values.

The constituent materials of the transparent electrode (2) other than the SnO ₂ include:
Other transparent metal oxides such as ITO and ZnO can be mentioned. These materials may be used in combination. Non-single-crystal semiconductors that make up the photoelectric conversion device include Si, SiC, SiN, and SiG
e, hydrogenated alloys such as SiSn (eg, a-SiC: H used for the p-layer (3) and a-Si: H used for the i-layer (4) in the examples)
And amorphous silicon-based semiconductors generally used for photovoltaic elements, such as fluorinated alloys. An amorphous semiconductor containing microcrystals as used for the n-layer (5) in the above embodiment may be used, or a polycrystalline semiconductor may be used. It is most preferable to arrange a p-layer (3) in which a-SiC: H is doped with an element of Group IIIb of the periodic table on the light-receiving surface side as in the above embodiment. However, an n-layer may be disposed on the light-receiving surface side, and in this case, it is optimal to use a-SiC: H doped with an element of the periodic table group Vb for the n-layer.

The optical bandgap and impurity concentration gradually increase between the p-layer (3) and the i-layer (4) or between the n-layer (5) and the i-layer (4) toward the i-layer (4). A decreasing layer may be provided. The thickness of the impurity semiconductor layer is suitably 30 ° or more and 500 ° or less, and more preferably 50 ° or more and 200 ° or less.

In order to reduce the contact resistance between the impurity semiconductor layer (p layer (3) or n layer) on the light receiving surface side and the transparent electrode (2), the same conductivity type high impurity layer as the light receiving surface side impurity semiconductor layer is used. A concentration doping layer may be provided. The thickness of the high-concentration doping layer is suitably from 5 ° to 100 °, more preferably from 10 ° to 50 °. The impurity concentration is suitably 5 times or more and 50 times or less of the impurity semiconductor layer on the light receiving surface side.

In the case of adopting a two-stage tandem structure in which two elements each including a p-layer, an i-layer and an n-layer are connected in tandem, it is effective to apply the present invention to elements farther from the light receiving surface.

[Effects of the Invention] As described above, the manufacturing method according to the present invention is a method for manufacturing a photoelectric conversion device including a non-single-crystal semiconductor in which an intrinsic semiconductor layer is provided between two impurity semiconductor layers having different conductivity types. Forming a first impurity semiconductor layer, performing a heat treatment on the layer at a temperature equal to or higher than the film formation temperature of the first impurity semiconductor layer, and forming a first impurity semiconductor layer at a temperature equal to or higher than the film formation temperature of the first impurity semiconductor layer. After forming the intrinsic semiconductor layer at a higher temperature,
Since the second impurity semiconductor layer is formed, deterioration of the initial conversion efficiency of the photoelectric conversion device can be suppressed while preventing the deterioration. Therefore, according to the present invention, a highly efficient and highly reliable photoelectric conversion device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a solar cell manufactured by a method according to an embodiment of the present invention, FIG. 2 is a graph showing initial external characteristics of the solar cell of the preceding figure, and FIG. 3 is a diagram showing initial external characteristics of a comparative example. It is a graph. DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Transparent electrode, 3 ... P layer, 4 ...
... i layer, 5 ... n layer, 6 ... back electrode.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-33919 (JP, A) JP-A-57-1272 (JP, A) JP-A-2-82655 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H01L 31/04 H01L 31/10

Claims (1)

(57) [Claims] 1. A method for manufacturing a photoelectric conversion device comprising a non-single-crystal semiconductor in which an i-type intrinsic semiconductor layer is provided between two p-type and n-type impurity semiconductor layers having different conductivity types. Forming a layer or an n-layer first impurity semiconductor layer;
After performing a heat treatment on this layer at a temperature equal to or higher than the film formation temperature of this layer, and forming an intrinsic semiconductor layer at a temperature equal to or higher than the film formation temperature of the first impurity semiconductor layer, forming a second impurity semiconductor layer of an n-layer or a p-layer, wherein the heat treatment temperature of the first impurity semiconductor layer is 100 ° C. or more and 400 ° C.
A method for manufacturing a photoelectric conversion device, wherein the deposition temperature of an intrinsic semiconductor layer is 100 ° C. or more and 400 ° C. or less.