JP3520683B2 - Compound semiconductor thin film, method for manufacturing the same, and solar cell - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a compound semiconductor thin film, a method for manufacturing the same, and a solar cell.

[0002]

2. Description of the Related Art I used as a light absorption layer for solar cells
Semiconductor thin films made of Group III, Group III, and Group VI elements have a large light absorption coefficient, and are attracting attention as solar cell materials that can be thinned. For example, it has been reported that a solar cell using a Cu (In, Ga) Se ₂ thin film as a light absorption layer has an advantage that theoretical conversion efficiency is high and efficiency is not deteriorated by light irradiation or the like. . The Cu (In, Ga) Se ₂ thin film currently used for the solar cell showing high conversion efficiency is Ga / (In
+ Ga) ratio is about 0.2 to 0.3, and the band gap is about 1.2 eV.

On the other hand, on the surface of this high-efficiency Cu (In, Ga) Se ₂ thin film, Cu (In, Ga) ₃ which is an In, Ga excess phase is formed.
It is said that Se ₅ exists, and Cu (In, Ga) ₃ Se _{5 is present.}
Has been reported on its crystal structure and its physical properties. For example, in 1995 Progress in Photovoltaics, Volume 3, Volume 6 (Progress in Photovoltaics, V
ol.3, No.6,1995), shocks (W.Schock), etc. are caused by solar cells based on CuInSe ₂ and
Relayed Compounds: Material and Proceedings (Solar Cells Based on CuInSe ₂ and Rela
ted Compounds: Material and Device Properties and P
CuIn with excessive composition of In and Ga
A CuIn ₃ Se ₅ phase exists on the surface of the Se ₂ thin film, and a CuGaSe ₂ thin film in which In is replaced by Ga and a CuInS ₂ thin film in which Se is replaced by S are CuIn ₅ Se ₈ phase and CuIn ₅ S.
e It has been reported that it changes to phase ₈ . However, the details of the change in crystal structure due to the difference in the solid solution rates of group III elements and group VI elements are not clear. Others Cu (In, Ga) ₃ Se
_{As an} example of the report on the physical properties of _5, the Applied Physics Letter (1995)
tters, Vol.67, No.6,1995)
And characterization of Cu (In
_1-x Ga _x ) ₃ Se ₅ Thin Films (Preparation and
Characterization of Cu (In, Ga) ₃ Se ₅ thin films), with the same Ga content, Cu (In, Ga) ₃ S
e ₅ has a larger band gap than Cu (In, Ga) Se ₂ , and Cu (I
It has been reported that the band gap of n, Ga) ₃ Se ₅ increases. In addition, the 25th IEEE International Conference on Solar Energy Conversion (25th IEEE First Conference) held in May 1996.
World Conference on Pkotovoltaic Energy Conversio
In n), M. Contreras and the like are defective chalcopyrite Cu (In, Ga) ₃ Se ₅ Polycrystalline thin film materials (Defect
Chalcopyrite Cu (In, Ga) ₃ Se ₅ Polycrystalline Thin-Fi
lm Materials), like us, Cu (In, G) having a defective chalcopyrite structure with the same Ga content
a) Cu (In, Ga) with ₃ Se ₅ phase having chalcopyrite structure
It was reported that the band gap was about 200 meV larger than that of the Se ₂ phase, and the conductivity type, which was n-type in CuIn ₃ Se ₅ , became p-type when the Ga / (In + Ga) ratio was 0.3 or more. It will change. But Cu
Since (In, Ga) ₃ Se ₅ has a high resistance value of about 10 ⁶ Ω-cm, its details including measurement error and the like cannot be understood.

[0004]

According to the above reports, Cu
When (In, Ga) Se ₂ is applied to the light absorption layer of a solar cell, it is necessary to match the bandgap of Cu (In, Ga) Se ₂ with the solar spectrum, but the solar cells that currently show high conversion efficiency. Cu (In, G) used in batteries
a) The Se ₂ thin film has a Ga / (In + Ga) ratio of 0.2 to 0.
It is about 3 and the band gap is about 1.2 eV. Therefore, in order to obtain higher conversion efficiency, the Ga concentration is further increased, and Ga / (In + Ga) ≈0.7 and the band gap is 1.5 eV. Need to be about. However, if Ga concentration is increased for the purpose of widening the band gap, Cu
Cu containing many defects such that the crystallinity of (In, Ga) Se ₂ is lowered and the generated carriers are eliminated by absorbing light.
This results in a (In, Ga) Se ₂ thin film, resulting in a decrease in conversion efficiency of the solar cell. However, when the Ga / (In + Ga) ratio for obtaining a high-quality film is about 0.2 to 0.3, the band gap is small and the loss becomes large when considering the matching with the sunlight spectrum. The highest theoretical conversion efficiency calculated is also low. Therefore, an important issue is how to obtain a high-quality film having a low Ga concentration and a light absorption layer having a large band gap that matches the sunlight spectrum.

In addition, the band gap of the same Ga content
Large Cu (In, Ga)₃Se_FiveApplied to the light absorption layer
In order to achieve this, Cu, which was conventionally thought to exhibit an n-type conduction type,
In ₃Se_FiveBecomes a p-type conduction type by containing Ga
However, under the condition that Group Ia is added, Cu (In,
Ga)₃Se_FiveOf In and Ga to form p-type
No details are given regarding the range, and the
Cu due to impurity elements such as Na diffused and mixed from
(In, Ga)₃Se_FiveHow is it affected
I don't know.

[0006]

In order to solve the above problems, the present invention contains a group Ia element [Cu ₂ (S _z S
_{e 1- z)] x [(} In 1-y Ga y) 2 (S z Se 1-z) 3] provides _1-x compound semiconductor thin film. However, 0.16 ≦ x ≦ 0.3
4, 0.05 ≦ y ≦ 0.55 and 0 ≦ z ≦ 1.0.

It is preferable to use at least one of Li, Na and K as the group Ia element.

The content of the Group Ia element is preferably set to 1 mol% as an upper limit. The present invention provides a manufacturing method using at least one kind of Li compound, Na compound, and K compound as a vapor deposition source of a group Ia element.

Here, Li ₂ O and Li ₂ O are used as the Li compound.
₂ , Li ₂ S, Li ₂ Se, Li ₂ Te, LiF, LiC
It is preferable to use at least one of l, LiBr, and LiI.

Na ₂ O and Na ₂ O are used as Na compounds.
₂ , Na ₂ S, Na ₂ Se, Na ₂ Te, NaF, NaC
It is preferable to use at least one of 1, 1, NaBr, and NaI.

Further, as K compounds, K ₂ O, K ₂ O ₂ ,
K ₂ S, K ₂ Se, K ₂ Te, KF, KCl, KBr, K
It is preferable to manufacture using at least one kind of I.

The present invention also provides [Cu ₂ (S _z Se _1-z )].
the configuration elements _{x [(In 1-y Ga} y) 2 (S z Se 1-z) 3] 1- x compound, a production method using at least one kind of simple substance or compounds of the respective elements provide.

Further, the above compound is used as an inert gas or
It is preferable to perform the heat treatment in an atmosphere using at least one kind of VIb group element vapor.

The present invention also provides a solar cell using the compound semiconductor thin film as a light absorbing layer.

According to the present invention described above, containing Group Ia _{[Cu 2 (S z Se 1} -z)] x [(In 1- y Ga y) 2 (S z Se
_1-z ) ₃ ] _1-x compound semiconductor thin film (provided that 0.16 ≦ x ≦ 0.
34, 0.05 ≦ y ≦ 0.55, 0 ≦ z ≦ 1.0), the conductivity of the semiconductor thin film is improved by adding the group Ia element, and a semiconductor thin film not containing the group Ia is added. In comparison, it is possible to obtain a conduction type that functions as a light absorption layer of a solar cell for a limited range of x and y values. Here, by setting 0.16 ≦ x ≦ 0.34, single-phase Cu (In, G) having a band gap larger than Cu (In, Ga) Se ₂ having the same Ga content.
a) It is possible to obtain a ₃ Se ₅ thin film, and it is possible to obtain a compound semiconductor thin film having a band gap that matches the sunlight spectrum with a small Ga content. Further, by setting 0.05 ≦ y ≦ 0.55, Cu (I) having a conduction type (p-type) that functions as a light absorption layer of a solar cell
n, Ga) ₃ Se ₅ thin film can be obtained, and Cu (In, Ga) Se ₂ with y ≧ 0.5 in the same bandgap can be obtained.
It is possible to obtain a compound semiconductor thin film having a crystallinity superior to that of the film and having a bandgap more matched to the sunlight spectrum.

Further, by using at least one of Li, Na and K as the group Ia element, Cu (In,
It becomes possible to promote the crystal growth of the Ga) ₃ Se ₅ thin film and improve the conductivity.

Furthermore, [Cu ₂ (S, Se)] _x [(In _1-y
Ga _y ) ₂ (S, Se) ₃ ] _{1-x I in the} compound semiconductor thin film
By setting the proportion of the group a element to 1 mol% as the upper limit,
_{[Cu 2 (S, Se)} ] x [(In 1-y Ga y) 2 (S, Se) 3]
It becomes possible to mix the group Ia element without changing the composition of the _1-x thin film.

Li compound, N as a vapor deposition source of the group Ia element
By using at least one of the a compound and the K compound, the group Ia element [Cu
_{2 (S z Se 1-z} )] x [(In 1-y Ga y) 2 (S z Se 1-z) 3]
It becomes possible to mix it into the _1-x compound semiconductor thin film, which is an effective means for promoting the crystal growth and improving the conductivity of the compound semiconductor thin film.

Li ₂ O, Li ₂ O ₂ , L as Li compounds
i ₂ S, Li ₂ Se, Li ₂ Te, LiF, LiCl, L
At least one of iBr and LiI is used, and Na ₂ O, Na ₂ O ₂ , Na ₂ S, and Na ₂ are used as Na compounds.
Se, Na ₂ Te, NaF, NaCl, NaBr, Na
At least one of I is used, and K ₂ O, K ₂ O ₂ , K ₂ S, K ₂ Se, K ₂ Te, KF, and K are used as K compounds.
By producing at least one of Cl, KBr, and KI, the group Ia element can be stabilized by [Cu
_{2 (S, Se)] x} [(In 1-y Ga y) 2 (S, Se) 3] 1-x compound it is possible to incorporate into the semiconductor thin film, effectively a compound semiconductor thin film crystal growth of Can be promoted and the conductivity can be improved.

[Cu ₂ (S _z Se _1-z )] _x [(In _1-y
Ga _y ) ₂ (S _z Se _1-z ) ₃ ] _1-x For the constituent elements of the compound, various deposition sources can be selected by manufacturing using at least one of the constituent elements alone or a compound. In addition to its flexibility and flexibility, it also enables precise and easy composition control.

Further, the above compound is used as an inert gas or
[Cu ₂ (S _z Se _{1 -z} )] by heat treatment in an atmosphere using at least one kind of VIb group element vapor
_{x [(In 1 -y Ga y} ) 2 (S z Se 1-z) 3] 1-x compound thin film to reduce the defects present, it is possible to higher quality thin film preparation.

By using the above compound semiconductor thin film for the light absorption layer of a solar cell, a highly efficient thin film solar cell can be manufactured.

Furthermore, as a light absorption layer of the solar cell, 0.1
6 ≦ x ≦ 0.34, 0.05 ≦ y <0.55, 0 ≦ z ≦
1.0 _{[Cu 2 (S z Se 1} -z)] x [(In 1-y Ga y) 2 (S
_{By using a z} Se _1-z ) ₃ ] _1-x compound semiconductor thin film, a highly efficient thin film solar cell can be manufactured.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Example 1) [Cu ₂ (S _z Se _1-z )] _x [(In _1-y Ga _y )] containing the group Ia element in this example.
_{The 2} (S _z Se _1-z ) ₃ ] _1-x compound semiconductor thin film will be described. FIG. 1 shows a schematic view of a vacuum container used for forming a Cu (In, Ga) ₃ Se ₅ thin film. A substrate holder 2 and a tantalum heater 3 for heating the substrate are provided inside a vacuum container 1 having an exhaust port 7 shown in FIG. 1, and an alumina substrate 4 coated with a Mo film 5 of about 1 μm is used as a group Ia vapor deposition source. Na ₂ S12
Was vapor-deposited on the Mo film at a vapor deposition rate of 100 L / min for 10 minutes. On top of that, x = 0.25, y = 0.2,
Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film 6 with z = 0 is about 2 μm.
m form. Upon _{Cu (In 0.8 Ga 0.2) 3} Se 5 film deposition, _{Cu (In 0.8 Ga 0.2) 3} Se 5 and the evaporation source 8 of Cu which is a main component of the thin film, In the evaporation source 9, Ga deposition source 10 of, A vapor deposition source 11 of Se was prepared, and simultaneous vapor deposition of each element was performed. At this time, the temperatures of the crucibles containing the respective vapor deposition sources are heated at a constant temperature of 1150 ° C., 850 ° C., 900 ° C., and 200 ° C., and the vapor deposition rates of Cu, In, Ga, and Se become the stoichiometric composition Cu ( The rate is such that an In _0.8 Ga _0.2 ) ₃ Se ₅ thin film can be obtained. Here, the substrate temperature is 500
The temperature was constant.

In Table 1, Cu (In _0.8
Ga _0.2 ) ₃ Se ₅ thin film and Cu without addition of Na element
The conductivity of the (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film is shown.

[0027]

[Table 1]

From this table, Cu which was vapor-deposited with Na ₂ S at the same time
_{(In 0.8 Ga 0.2) 3 Se} 5 film is Na ₂ S increases approximately 2 Ketashirube conductivity than the membrane that was not co-deposited, to have a conductivity suitable for the light absorption layer of a solar cell Recognize. That is, Cu (In _0.8 Ga _0.2 ) S was obtained by adding Na, which is a group Ia, to a Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film.
It is possible to improve the conductivity of e ₂ .

Next, the above-mentioned two types of Cu (In _0.8 Ga _0.2 )
_A solar cell was prepared in order to apply the ₃ Se ₅ thin film to the light absorption layer of the solar cell. FIG. 2 shows the structure of the solar cell. Each manufacturing method will be described below. Alumina substrate 4
Approximately 1 Mo film 5 which is the back electrode on the
Then, a Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film 5 is formed to a thickness of about 2 μm. Further, a CdS thin film 14 having a thickness of about 500 Å is formed thereon by a solution deposition method, and a ZnO thin film 15 having a thickness of 0.5 μm and IT is formed thereon by a sputtering method.
The O thin film 16 was formed to a thickness of 1 μm. Furthermore, ITO
An Au electrode 17 having a thickness of 0.5 μm was formed as a take-out electrode on the film and the Mo thin film by a vacuum evaporation method.

FIG. 3 shows the above-mentioned Na-added Cu (In _0.8
3 shows the spectral sensitivity characteristics of a solar cell using a Ga _0.2 ) ₃ Se ₅ thin film as a light absorption layer. The spectral sensitivity characteristics were measured under the conditions of AM 1.5 and 100 mW / cm ² . C
ITO formed on the u (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film
Since / ZnO / CdS shows an n-type conduction type, x =
0.25, y = 0.2 Cu (In _0.8 Ga _0.2 ) ₃ Se ₅
The thin film is considered to be a p-type conductive type, and can be applied to the light absorption layer of a solar cell. Note that N
Spectral sensitivity characteristics could not be obtained from a solar cell having the same structure using a Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film to which a was not added as a light absorption layer. That Ia profane and unless x = 0.25 containing, y = at 0.2 conditions _{Cu (In 0 .8 Ga 0.2)} 3 Se 5 film does not become the p-type,
Does not function as a light absorption layer.

Next, Cu containing ya at a constant y = 0.2 and x = 0.5 and 0.25 containing a group Ia element was prepared on a glass substrate.
(In _0.8 Ga _0.2 ) Se ₂ , Cu (In _0.8 Ga _0.2 ) ₃ S
Table 2 shows the calculated band gap values obtained by plotting (hν) vs (αhν) ² from the transmission characteristics of the e ₅ thin film.

[0032]

[Table 2]

From this table, the film with x = 0.25 has x =
It can be seen that the band gap is larger than that of the film of 0.5. Here, Cu (In _0.8 Ga) with x = 0.25
_{0.2) 3} crystal structure of Se ₅ is defective chalcopyrite structure, x = 0.5 in the _{Cu (In 0 .8 Ga 0.2)} Se 2 is known from the result that a chalcopyrite structure of the X-ray diffraction . Considering matching with the sunlight spectrum, the light absorption layer of the thin-film solar cell ideally has a band gap of about 1.4 to 1.5 eV, and thus the thin-film sample prepared this time (y = 0. In 2), it can be seen that the film having the defective chalcopyrite structure has a more ideal band gap. From this, x =
0.25, y = 0.2 Cu (In _0.8 Ga _0.2 ) ₃ Se ₅
By applying the thin film to the light absorption layer of a solar cell, it is possible to manufacture an ideal solar cell.

Next, the defect chalcopyrite structure I
[Cu containing group a element₂(S_zSe _1-z)]_x[(In_1-y
Ga_y)₂(S_zSe_1-z)₃]_1-xThe condition range of x in
For this purpose, the value of x was changed from x = 0.1 to 0.5
[Cu₂(S_zSe_1-z)]_x[(In_{1 -y}Ga_y)₂(S_zS
e_1-z)₃]_1-xA thin film (y = 0.2, z = 0) was prepared.

The thin film sample prepared in FIG. 4 (x = 0.1,
The X-ray diffraction pattern of 0.3, 0.5) is shown. x = 0.
From the sample of No. 1, Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ and (In
_0.8 Ga _0.2) diffraction pattern is obtained seems to ₂ Se _3,
It seems that the film is formed in a form in which the two components are mixed. On the other hand, from the sample of x = 0.3, only the diffraction pattern showing the Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ phase of the defect chalcopyrite structure was obtained, and the same single phase C as x = 0.25 was obtained.
It can be seen that a u (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film is formed. Further, it can be seen that when x = 0.5, only the Cu (In _0.8 Ga _0.2 ) Se ₂ phase having a chalcopyrite structure is formed, and peaks such as 110, 202, and 114 peculiar to the defective chalcopyrite phase are not observed. The defect chalcopyrite structure Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film is a chalcopyrite structure Cu (In _0.8 Ga _0.2 ) S.
has a larger bandgap than the e ₂ thin film, and y =
At 0.2, it has a value closer to the band gap that matches the sunlight spectrum. From the above results, single-phase Cu having a defective chalcopyrite structure at x = 0.3
It was found that a (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film was formed.

When the composition region of the defective chalcopyrite structure around x = 0.3 was examined precisely,
Cu (In _0.8 Ga _0.2 ) ₃ having a single-phase defect chalcopyrite structure in the range of 0.16 ≦ x ≦ 0.34
It was found that a Se ₅ thin film was formed. From this fact, in the range of 0.16 ≦ x ≦ 0.34, Cu (In _0.8 Ga _0.2 ) _{3 having a} single-phase defect chalcopyrite structure having a band gap larger than that of the Cu (In _0.8 Ga _0.2 ) Se ₂ thin film having chalcopyrite structure. It is possible to obtain a Se ₅ thin film.

Next, Ia having a function as a light absorption layer
[Cu ₂ (S _z Se _{1- z} )] _x [(In _1-y G containing a group element
a _y ) ₂ (S _z Se _1-z ) ₃ ] _{1-x In} order to investigate the condition range of y, the value of y is changed from y = 0 to 1.0 in steps of 0.1 and Cu (In _{1 -y} Ga _{y) 3} Se ₅ film (x = 0.25, z
= 0) was produced.

FIG. 5 shows the change in conductivity with respect to the value of y (= Ga / (In + Ga)). From this figure, it can be seen that the conductivity decreases when y = 0.6 or more. Also,
Cu (In _1-y G) prepared on a glass substrate by adding Na
From the transmission characteristics of the a _y ) ₃ Se ₅ thin film, (hν) vs (αh
The band gap calculated by plotting ν) ² is shown in FIG. From this figure, it is found that the bandgap becomes about 1.5 eV near y = 0.5, which is the optimum bandgap for the light absorption layer of the solar cell. Further, when a solar cell having the same structure is manufactured using a GaIn-free (y = 0) CuIn ₃ Se ₅ thin film, quantum efficiency cannot be obtained, so that a Ga-free (y = 0) CuIn ₃ Se ₅ thin film is It can be seen that the n-type conductivity type is shown, and that by including Ga, it functions as a light absorption layer of the solar cell and changes to the p-type. Considering together with the changes in conductivity and conductivity type described above, the light absorption layer (p-type) having relatively good conductivity and having an optimum band gap in the range of 0.05 ≦ y ≦ 0.55.
_{Cu (In 1-y Ga y} ) 3 Se 5 thin film forming is made possible.

Here, [Cu ₂ (S, Se)] _x [(I
_{n 1-y Ga y) 2} (S, Se) 3] 1-x compound semiconductor thin film z =
0 (Cu, In, Ga) ₃ Se ₅ thin film
Similar results are obtained for the thin film sample containing S.

(Embodiment 2) Next, in the second embodiment
[Cu ₂ (S _z Se _1-z )] _x [(In
_{1-y Ga y) 2 (} S z Se 1-z) 3] 1-x compound semiconductor thin film described. The conditions for forming the thin film are almost the same as those in the first embodiment, but L is used instead of Na ₂ S12 as a vapor deposition source of group Ia.
i ₂ S was prepared, vapor deposition was performed on the Mo film for 10 minutes at a vapor deposition rate of 100 Å / min., and then x = 0.25, y = 0.
2, a Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film with z = 0 was formed to manufacture a solar cell having the same structure as that of Example 2, and the same result as that of Example 2 was obtained. That is, the vapor deposition source of Group Ia is not limited to the Na compound.

Similar results could be obtained by using other K compounds or their respective mixtures.

(Third Embodiment) Next, a third embodiment will be described.
[Cu ₂ (S _z Se _1-z )] _x [(In
_{1-y Ga y) 2 (} S z Se 1-z) 3] 1-x compound semiconductor thin film described. The conditions for forming the thin film are almost the same as those in the first embodiment, but vapor deposition is carried out for 10 minutes at vapor deposition rates of 100 Å / min. And 200 Å / min. In Na ₂ S12 which is a group Ia vapor deposition source, and then x = 0. C of 0.25, y = 0.2, z = 0
A thin film of u (In _0.8 Ga _0.2 ) ₃ Se _{5 was} formed.

The composition of the prepared Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film was analyzed by EPMA. As a result, 100 Å / min.
In from films deposited Na ₂ S Na not is hardly detected, from the film with a deposit of Na ₂ S at 200 Å / min. Na was detected 1.5 mol%.

A solar cell having the same structure as in Example 1 was produced from these two thin films. As a result, 200Å / mi
The solar cells with Na ₂ S deposited film at n. showed lower collection efficiency. This is because Na is Cu (In _0.8 Ga _0.2 ) ₃ S
e ₅ Cu (In _0.8 Ga _0.2 ) ₃ because a large amount was mixed in the thin film
It is considered that the composition of Se ₅ changed and, as a result, the solar cell characteristics deteriorated. Therefore, Cu (In _0.8 Ga _0.2 )
_It is desirable that the Na content is such that the composition of ₃ Se ₅ does not change, and Cu having the optimum composition by setting 1 mol% as the upper limit.
It becomes possible to apply the (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film to the light absorption layer of a solar cell.

(Embodiment 4) Next, in the fourth embodiment
[Cu ₂ (S _z Se _1-z )] _x [(In
_{1-y Ga y) 2 (} S z Se 1-z) 3] 1-x compound semiconductor thin film described. The conditions for forming the thin film are almost the same as those in the first embodiment, but a solar cell having the same structure as that of the first embodiment is manufactured by using Na ₂ O ₂ as the Na compound. As a result, Example 1
It was possible to obtain almost the same result as.

In addition, Na is used as a Na compound.₂O, Na₂
S, Na₂Se, Na₂Te, NaF, NaCl, NaB
r, NaI, Li as a Li compound₂O, Li₂O₂, L
i₂S, Li₂Se, Li₂Te, LiF, LiCl, L
iBr, LiI, or K as a K compound₂O, K₂O₂,
K₂S, K₂Se, K₂Te, KF, KCl, KBr, K
Almost the same result can be obtained by using at least one of I
I got it, but Na ₂The effect when S is used
Was more prominent.

(Fifth Embodiment) Next, in the fifth embodiment
[Cu ₂ (S _z Se _1-z )] _x [(In
_{1-y Ga y) 2 (} S z Se 1-z) 3] 1-x compound semiconductor thin film described. The conditions for forming the thin film are almost the same as those of the first embodiment, but Cu vapor deposition source 8, In vapor deposition source 9, Ga vapor deposition source 10, Se vapor deposition source 11 are used as vapor deposition sources of Cu (In _0.8 Ga _0.2 ) ₃ Se _5. Instead of Cu ₂ Se, In ₂ Se ₃ , Ga ₂ Se
₃ by the respective co-deposition using Cu (In _0.8 Ga
_An attempt was made to form a _0.2 ) ₃ Se ₅ thin film. Also in this case, the substrate temperature is about 500 ° C.

As a result of the X-ray diffraction analysis, an X-ray diffraction pattern showing the same orientation as the Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ thin film prepared in Example 1 was obtained. Further, when a solar cell having the same structure as that of Example 1 was manufactured using this film, the same collection efficiency as that of Example 1 could be obtained.
_{That, Cu (In 0.8 Ga 0.2)} 3 Se 5 film formation is not limited to the co-deposition from each independent respective elements were.

(Embodiment 6) Next, in the sixth embodiment
[Cu ₂ (S _z Se _1-z )] _x [(In
_{1-y Ga y) 2 (} S z Se 1-z) 3] 1-x compound semiconductor thin film described. The conditions for forming the thin film are almost the same as those of the first embodiment, but the prepared Cu (In _0.8 Ga _0.2 ) ₃ Se ₅ is used as Se.
Heat treatment was performed at 400 ° C. for 30 minutes in the atmosphere. As a result, the solar cell characteristics could be slightly improved as compared with the sample that was not heat-treated. This is Cu (In
It is considered that this is because the defects generated at the time of forming the _0.8 Ga _0.2 ) ₃ Se ₅ thin film could be reduced by performing the heat treatment.

In addition, the same effect could be obtained by using at least one kind of inert gas or VIb group element vapor as the heat treatment atmosphere.

[0051]

According to the present invention, [Cu ₂ (S _z Se _1-z )] _x [(In containing a high-quality Group Ia element having a conduction type and a band gap suitable for a light absorption layer of a solar cell is provided. _1-y Ga y)
₂ (S _z Se _1-z ) ₃ ] _1-x compound semiconductor thin film can be manufactured, and a solar cell with high conversion efficiency can be manufactured.

[Brief description of drawings]

Containing Ia group element in an embodiment of the invention, FIG _{[Cu 2 (S z Se 1} -z)] x [(In 1-y Ga y) 2 (S z Se
_1-z ) ₃ ] _1-x compound semiconductor thin film forming apparatus

Containing Ia group element in an embodiment of the present invention; FIG _{[Cu 2 (S z Se 1} -z)] x [(In 1-y Ga y) 2 (S z Se
_1-z ) ₃ ] _1-x Cross-section of solar cell using compound semiconductor thin film

Containing Ia group element in one embodiment of the present invention; FIG _{[Cu 2 (S z Se 1} -z)] x [(In 1-y Ga y) 2 (S z Se
_1-z ) ₃ ] _1-x Diagram showing the spectral sensitivity characteristics of solar cells using compound semiconductor thin films

Containing Ia group element in an embodiment of the present invention; FIG _{[Cu 2 (S z Se 1} -z)] x [(In 1-y Ga y) 2 (S z Se
_1-z ) ₃ ] _1-x compound semiconductor thin film X-ray diffraction pattern

Containing Ia group element in an embodiment of the present invention; FIG _{[Cu 2 (S z Se 1} -z)] x [(In 1-y Ga y) 2 (S z Se
_1-z ) ₃ ] _1-x diagram showing conductivity of compound semiconductor thin film

Containing Ia group element in an embodiment of the invention; FIG _{[Cu 2 (S z Se 1} -z)] x [(In 1-y Ga y) 2 (S z Se
_1-z ) ₃ ] _1-x Diagram showing the band gap of compound semiconductor thin film

[Explanation of symbols]

1 Vacuum Container 2 Substrate Holder 3 Tantalum Heater 4 Alumina Substrate 5 Mo Thin Film 6 Cu (In, Ga) ₃ Se ₅ Thin Film 7 Exhaust Port 8 Cu Source 9 In Source 10 Ga Source 11 Se Source 12 Na ₂ S Source 13 Shutter 14 CdS Thin film 15 ZnO thin film 16 ITO thin film 17 Au electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Wada 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-8-102546 (JP, A) JP-A-5- 175119 (JP, A) European patent application publication 715358 (EP, A 1) International publication 96/013063 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/203 H01L 21 / 363 H01L 31/04

Claims (10)

(57) [Claims] 1. A defective chalcopyrite structure, Ia
[Cu ₂ (S _z Se _1-z )] _x [In _1-y containing a group element
_{Ga y) 2 (S z Se} 1-z) 3] 1-x compound semiconductor thin film. However, 0.16 ≦ x ≦ 0.34, 0.05 ≦ y ≦ 0.5
5, 0 ≦ z ≦ 1.0. 2. The compound semiconductor thin film according to claim 1, wherein the group Ia element is at least one selected from the group consisting of Li, Na, and K. 3. The compound semiconductor thin film according to claim 1, wherein the content of the group Ia element is 1 mol% as an upper limit. 4. A vapor deposition source of a group Ia element is a Li compound, Na
The method for producing a compound semiconductor thin film according to claim 2, wherein the compound semiconductor thin film is at least one selected from the group consisting of compounds and K compounds. 5. The Li compound is Li ₂ O, Li ₂ O ₂ , Li ₂
S, Li ₂ Se, Li ₂ Te, LiF, LiCl, LiB
The method for producing a compound semiconductor thin film according to claim 4, wherein the compound semiconductor thin film is at least one selected from the group consisting of r and LiI. 6. The Na compound is Na ₂ O, Na ₂ O ₂ , Na ₂
S, Na ₂ Se, Na ₂ Te, NaF, NaCl, NaB
The method for producing a compound semiconductor thin film according to claim 4, wherein the compound semiconductor thin film is at least one selected from the group consisting of r and NaI. 7. The K compound is K ₂ O, K ₂ O ₂ , K ₂ S or K _2.
The method for producing a compound semiconductor thin film according to claim 4, wherein the compound semiconductor thin film is at least one selected from the group consisting of Se, K ₂ Te, KF, KCl, KBr, and KI. 8. [Cu ₂ (S _z Se _1-z )] _x [In _1-y G
The _ay ) ₂ (S _z Se _1-z ) ₃ ] _1-x compound is formed by using at least one kind of a group consisting of a simple substance or a compound of the constituent elements with respect to the constituent elements of the compound. Method for manufacturing compound semiconductor thin film. 9. The method for producing a compound semiconductor thin film according to claim 1, further comprising a step of performing heat treatment in an atmosphere using at least one selected from the group consisting of an inert gas and a VIb group element vapor. 10. A solar cell in which the light absorption layer comprises the compound semiconductor thin film according to any one of claims 1 to 3.