The present disclosure relates to a method for fabricating a solar cell element.
A solar cell element converts sunlight into electrical energy.
NPL 1: P. N. Vinod, J Mater Sci: Mater Electron 22 (2011) 1248
NPL 2: Jenny Nelson (2003), The physics of Solar Cells, Imperial college press, pp. 11-13.
The purpose of the present disclosure is to provide a method for fabricating a solar cell element having higher conversion efficiency.
The following items 1 to 3 solve the problem.
1. A method for fabricating a solar cell element, the method comprising:
a step (a) of preparing a laminate 1 and a chamber 5, wherein
a step (b) of bringing the laminate 1 into contact with the aqueous solution 6 in such a manner that the second surface 4b is immersed in the aqueous solution 6 after the step (a);
a step (c) of applying a voltage difference between an anode electrode 71 and the laminate 1 under an atmosphere of the inert gas 7 to form a Zn layer 81 on the second surface 4b after the step (b), wherein
the chamber 5 is filled with the inert gas 7,
the aqueous solution 6 contains Zn2+ ions having a concentration of not less than 1 mM and not more than 5 M,
the aqueous solution 6 contains no oxygen,
the anode electrode 71 is contact with the aqueous solution 6,
the laminate 1 is used as a cathode electrode,
the aqueous solution 6 has a temperature of not less than 10 degrees Celsius and not more than 60 degrees Celsius, and
the Zn layer 81 has a concave-convex structure on the surface thereof; and
a step (d) of exposing the Zn layer 81 to oxygen so as to convert the Zn layer 81 into a ZnO crystalline layer 82 after the step (c).
2. The method according to the item 1, wherein
3. The method according to the item 1, wherein
The solar cell element provided according to the present method has higher conversion efficiency.
In other words, when a solar cell element 101 provided according to the method is irradiated with sunlight, the sunlight is converted into electrical energy more efficiently to generate a voltage difference between the p-side group-III-group-V compound electrode layer 2 and the n-side group-III-group-V compound electrode layer 4.
The embodiment of the present disclosure will be described below with reference to the drawings.
(Step (a)): Preparation of Laminate and Chamber
In the step (a), a laminate 1 and a chamber 5 are prepared first.
As shown in
The p-type group-III-group-V compound semiconductor layer 31 is interposed between the p-side group-III-group-V compound electrode layer 2 and the n-type group-III-group-V compound semiconductor layer 32.
The n-type group-III-group-V compound semiconductor layer 32 is interposed between the first surface 4a and the p-type group-III-group-V compound semiconductor layer 31.
As shown in
The p-side group-III-group-V compound electrode layer 2 generally comprises a p-side contact layer 21 and a p-side window layer 22.
The p-type group-III-group-V compound semiconductor layer 31 generally comprises a p-type base layer 31a consisting of a p-type GaAs layer.
The n-type group-III-group-V compound semiconductor layer 32 generally comprises an n-type emitter layer 32a consisting of an n-type GaAs layer.
The n-side group-III-group-V compound electrode layer 4 generally comprises an n-side window layer 41 and an n-side contact layer 42.
The p-type group-III-group-V compound semiconductor layer 31 is in contact with the n-type group-III-group-V compound semiconductor layer 32 to form a pn-junction.
The method for preparing the laminate 1 is not limited. For more detail, see
As shown in
(Step (b)): Contact of Laminate into Aqueous Solution
The step (b) is performed after the step (a).
In the step (b), the laminate 1 is brought into contact with the aqueous solution 6 in such a manner that the second surface 4b is immersed in the aqueous solution 6. The n-side contact layer 42 consisting of GaAs is exposed on the second surface 4b.
As shown in
(Step (c)): Formation of Zn Layer by Electrolysis
The step (c) is performed after the step (b).
In the step (c), as shown in
The anode electrode 71 is in contact with the aqueous solution 6. It is preferable that the anode electrode 71 is immersed in the aqueous solution 6. An example of the anode electrode 71 is a platinum electrode, a gold electrode, a silver electrode, or a copper electrode. A platinum electrode and a gold electrode are preferred.
In the step (c), it is necessary that the aqueous solution 6 contains Zn2+ ions having a concentration of not less than 1 mM and not more than 5M. When the concentration is less than 1 mM, the Zn layer 81 is not formed efficiently. When the concentration is greater than 5 M, the efficiency of the obtained solar cell element is low, as demonstrated in the comparative example 1, which is described later.
It is necessary that the aqueous solution 6 has a temperature of not less than 10 degrees Celsius and not more than 60 degrees Celsius. When the temperature of the aqueous solution 6 is higher than 60 degrees Celsius, the conversion efficiency of the obtained solar cell element is low, as demonstrated in the comparative example 2, which is described later. When the temperature of the aqueous solution 6 is less than 10 degrees Celsius, an excessively long time is required to form the Zn layer 81.
It is necessary that the chamber 5 is filled with the inert gas 7. To be more exact, the chamber 5 is filled with the inert gas 7 except in the part occupied by the aqueous solution 6. In other words, the lower part of the chamber 5 is occupied by the aqueous solution 6, and the upper part of the chamber 5 is occupied by the inert gas 7. An example of the inert gas 7 is nitrogen gas, helium gas, neon gas, argon gas, krypton gas, or xenon gas.
When the chamber 5 is not filled with the inert gas 7, the conversion efficiency of the obtained solar cell element is low, as demonstrated in the comparative example 3, which is described later. Accordingly, the aqueous solution 6 is required not to contain oxygen.
As shown in
As shown in
(Step (d)): Conversion of Zn Layer into ZnO Crystalline Layer by Oxygen Contact
The step (d) is performed after the step (c).
In the step (d), as shown in
The entire Zn layer 81 may be converted into the ZnO crystalline layer 82. Instead of this, a part of the Zn layer 81 may be converted into the ZnO crystalline layer 82.
As shown in
The following example describes the present disclosure in more detail.
As shown in
First, a AlAs sacrifice layer 44 having a thickness of 100 nanometers was formed on a non-doped GaAs substrate 45 having a diameter of 4 inches and a thickness of 450 micrometers by a metal organic chemical vapor deposition method (hereinafter, referred to as an “MOCVD”).
Then, the laminate 1 was formed on the AlAs sacrifice layer 44 as below.
More particularly, an n-side contact layer 42 consisting of a Te-doped GaAs layer (dope concentration: 1.0×1019, thickness: 20 nanometers) was formed on the AlAs sacrifice layer 44 by an MOCVD method.
Next, an n-side window layer 41 consisting of a Si-doped InGaP layer (dope concentration: 1.0×1018, thickness: 100 nanometers) was formed on the n-side contact layer 42 by an MOCVD method.
An n-type emitter layer 32a consisting of a Si-doped GaAs (dope concentration: 1.0×1018, thickness: 100 nanometers) was formed on the n-side window layer 41 by an MOCVD method.
A p-type base layer 31a consisting of a Zn-doped GaAs (dope concentration: 1.0×1016, thickness: 2.5 micrometers) was formed on the n-type emitter layer 32a by an MOCVD method.
A p-side window layer 22 consisting of a Zn-doped InGaP layer (dope concentration: 1.0×1019, thickness: 50 nanometers) was formed on the p-type base layer 31 by an MOCVD method.
A p-side contact layer 21 consisting of a Zn-doped GaAs layer (dope concentration: 1.0×1019, thickness: 20 nanometers) was formed on the p-side window layer 22 by an MOCVD method.
In this way, the laminate 1 shown in
Then, as shown in
Subsequently, the resist film was removed with a peeling liquid. After another resist film (not illustrated) was formed on the AlAs sacrifice layer 44, a titanium film having a thickness of 50 nanometers and a gold film having a thickness of 250 nanometers were formed on the AlAs sacrifice layer 44 by an electron beam vacuum deposition method so as to form an obverse electrode 83.
Similarly, after another resist film (not illustrated) was formed on the p-side contact layer 21, a titanium film having a thickness of 50 nanometers and a gold film having a thickness of 250 nanometers were formed on the p-side contact layer 21 by an electron beam vacuum deposition method to form a reverse electrode 84.
These another resist films were removed. Subsequently, an isolation film 85 was formed on the side walls of the obverse electrode 83, the reverse electrode 84, and the laminate 1. This isolation film 85 was formed of an SiN film having a thickness of 300 nanometers. A resist film was formed and a dry-etching was performed so as to form an opening 86 in the isolation film 85. Thus, the laminate 1 shown in
As shown in
As shown in
As shown in
As shown in
The aqueous solution 6 was prepared as below beforehand. Bubbles of N2 gas were supplied to a Zn(NO3)2 aqueous solution having a concentration of 1 mM at a temperature of 10 degrees Celsius for one hour. In this way, the oxygen which had been contained in the aqueous solution was removed to obtain the aqueous solution 6.
The chamber 5 was filled beforehand with N2 gas.
Then, using a potentiostat 51, a voltage difference of 0.8 V was applied between the cathode electrode 1a and the anode electrode 71 for three minutes to form the Zn layer 81 on the surface (the second surface 4b) of the n-side contact layer 42. The temperature of the aqueous solution 6 was 10 degrees Celsius.
The cathode electrode la was taken out from the chamber 5. The cathode electrode 1a was washed for five minutes with ion-exchange water. Then, the cathode electrode 1a was exposed to N2 blow to dry the cathode electrode 1a. In this way, the Zn layer 81 having a concave-convex structure on the surface thereof was obtained.
The laminate 1 comprising the Zn layer 81 was exposed to atmospheric air for two days. In this way, as shown in
Finally, as shown in
In this way, the solar cell element 101 was obtained.
As shown in
In more detail, an anti-reflection coating 104 consisting of a MgF2 film having a thickness of 140 nanometers was formed on the ZnO transparent electrode layer 93 by an electron beam vacuum deposition method.
As shown in
The solar cell element 101 was fixed at the focal point of the condenser lens 102 to obtain the solar cell 110.
The interface resistance value of the obtained solar cell 110 was measured in accordance with a TLM method, which was disclosed in Non-Patent Literature 1. During the measurement, the condenser lens 102 was irradiated with pseudo-sunlight, which was described later.
The conversion efficiency of the obtained solar cell 110 was calculated as below.
The condenser lens 102 was irradiated with a pseudo-sunlight having an output energy of 100 mW/cm2.
The pseudo-sunlight was radiated from the lamp where a xenon lamp (available from Wacom Co., Ltd.) of 500 watts and a halogen lamp (available from Wacom Co., Ltd.) of 400 watts were combined together.
The open circuit voltage Voc was measured when the obverse electrode 83 and the reverse electrode 84 were electrically opened.
The short-circuit current Isc was measured when the obverse electrode 83 and the reverse electrode 84 were short-circuited.
An I-V curve line as shown in
On the basis of
The fill factor FF was calculated in accordance with the following formula.
Here, Vmax means the voltage when the V·I value of the I-V curve is maximum (see the arrow in
Imax means the electric current when the V·I value of the I-V curve is maximum (see the arrow in
The conversion efficiency is calculated in accordance with the following formula.
Conversion efficiency=Voc·Jsc·FF
Here, Jsc=Isc/S
S (effective light-receiving surface area)=25,000 square micrometers.
The results are shown in Table 1.
An experiment similar to the example 1 was conducted except that the Zn(NO3)2 aqueous solution had a concentration of 5 M. The result is shown in
An experiment similar to the example 1 was conducted except that the Zn(NO3)2 aqueous solution had a temperature of 60 degrees Celsius. The result is shown in
An experiment similar to the example 1 was conducted except that the Zn(NO3)2 aqueous solution had a concentration of 5 M and a temperature of 60 degrees Celsius. The result is shown in
An experiment similar to the example 1 was conducted except that the Zn(NO3)2 aqueous solution had a concentration of 7 M and a temperature of 60 degrees Celsius. The result is shown in
An experiment similar to the example 1 was conducted except that the Zn(NO3)2 aqueous solution had a temperature of 70 degrees Celsius. The result is shown in
An experiment similar to the example 1 was conducted except that the chamber 5 was filled with atmospheric air. The result is shown in
As is clear from Table 1, in order to achieve higher efficiency, it is necessary that all of the following items (1) to (3) are satisfied when the Zn layer 81 is formed.
(1) The concentration of the Zn2+ is not less than 1 mM and not more than 5 M (see the comparative example 1).
(2) The temperature of the aqueous solution is not less than 10 degrees Celsius and not more than 60 degrees Celsius (see the comparative example 2).
(3) The Zn layer 81 is formed under an atmosphere of inert gas (see the comparative example 3).
Industrial Applicability
The present disclosure provides a method for fabricating a solar cell element having higher conversion efficiency.
This is a continuation of International Application No. PCT/JP2012/003539, with an international filing date of May 30, 2012, which claims priority of U.S. Provisional Patent Application No. 61/562,053 filed on Nov. 21, 2011, the contents of which are hereby incorporated by reference.
Number | Name | Date | Kind |
---|---|---|---|
5804466 | Arao et al. | Sep 1998 | A |
20100200060 | Liu | Aug 2010 | A1 |
Number | Date | Country |
---|---|---|
0794270 | Sep 1997 | EP |
Entry |
---|
Elias et al. (‘Effect of the Chemical Nature of the Anions on the Electrodeposition of ZnO Nanowire Arrays’—2008), J. Phys. Chem. C 2008, 112, 5736-5741. |
Yun et al., “Deposition and Characterization of TCO Films for the Application in GaAs Solar Cells,” Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, IEEE, May 7-12, 2006, pp. 823-825. |
Zou et al., “Orientation enhancement of polycrystalline ZnO thin films through termal oxidation of electrodeposited zinc metal,” Materials Letters, ScienceDirect, vol. 61, No. 21, Feb. 6, 2007, pp. 4305-4308. |
Su et al., “Antireflective and Radiation Resistant ZnO Thin Films for the Efficiency Enhancement of GaAs Photovoltaics,” Journal of the Electrochemical Society, vol. 158, No. 3, Jan. 7, 2011, pp. H267-H270. |
Lee et al., “Thin Film GaAs Solar Cells on Glass Substrates by Epitaxial Liftoff,” 25th PVSC, IEEE, May 13-17, 1996, pp. 53-55. |
P.N. Vinod, “Specific contact resistance measurements of the screen-printed Ag thick film contacts in the silicon solar cells by three-point probe methodology and TLM method,” J Mater Sci: Mater Electron, (2011) 22:1248-1257. |
J. Nelson, “The Physics of Solar Cells,” Imperial College Press (2003), pp. 11-13. |
International Search Report issued in International Application No. PCT/JP2012/003539 mailed Jun. 3, 2013, 3 pgs. |
Number | Date | Country | |
---|---|---|---|
20140106499 A1 | Apr 2014 | US |
Number | Date | Country | |
---|---|---|---|
61562053 | Nov 2011 | US |
Number | Date | Country | |
---|---|---|---|
Parent | PCT/JP2012/003539 | May 2012 | US |
Child | 14104763 | US |