CA2093707A1 - Methods for deposition of low resistivity semiconductors and fabrication of solar cells - Google Patents
Methods for deposition of low resistivity semiconductors and fabrication of solar cellsInfo
- Publication number
- CA2093707A1 CA2093707A1 CA002093707A CA2093707A CA2093707A1 CA 2093707 A1 CA2093707 A1 CA 2093707A1 CA 002093707 A CA002093707 A CA 002093707A CA 2093707 A CA2093707 A CA 2093707A CA 2093707 A1 CA2093707 A1 CA 2093707A1
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- Canada
- Prior art keywords
- fabrication
- solar cells
- electrolyte
- dopant
- semiconductor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 39
- 239000004065 semiconductor Substances 0.000 title claims abstract description 31
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 230000008021 deposition Effects 0.000 title abstract description 32
- SBIBMFFZSBJNJF-UHFFFAOYSA-N selenium;zinc Chemical compound [Se]=[Zn] SBIBMFFZSBJNJF-UHFFFAOYSA-N 0.000 claims abstract description 38
- 239000003792 electrolyte Substances 0.000 claims abstract description 37
- 239000010409 thin film Substances 0.000 claims abstract description 18
- 239000002019 doping agent Substances 0.000 claims description 19
- 239000000758 substrate Substances 0.000 claims description 16
- 238000002360 preparation method Methods 0.000 claims description 8
- 229910052738 indium Inorganic materials 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 229910052733 gallium Inorganic materials 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 229910004613 CdTe Inorganic materials 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims 2
- 238000000151 deposition Methods 0.000 abstract description 33
- 150000002500 ions Chemical class 0.000 abstract description 17
- 239000010408 film Substances 0.000 abstract description 16
- 238000004070 electrodeposition Methods 0.000 abstract description 13
- 229910052717 sulfur Inorganic materials 0.000 abstract description 8
- 229910052725 zinc Inorganic materials 0.000 abstract description 8
- 229910052711 selenium Inorganic materials 0.000 abstract description 6
- 229910052793 cadmium Inorganic materials 0.000 abstract description 4
- 239000012535 impurity Substances 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 6
- 239000011521 glass Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 238000007598 dipping method Methods 0.000 description 3
- 229910018162 SeO2 Inorganic materials 0.000 description 2
- JPJALAQPGMAKDF-UHFFFAOYSA-N selenium dioxide Chemical compound O=[Se]=O JPJALAQPGMAKDF-UHFFFAOYSA-N 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 1
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005441 electronic device fabrication Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910000337 indium(III) sulfate Inorganic materials 0.000 description 1
- 230000007775 late Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 230000003334 potential effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 238000007738 vacuum evaporation Methods 0.000 description 1
- 229910000368 zinc sulfate Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F10/00—Individual photovoltaic cells, e.g. solar cells
- H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
- H10F10/16—Photovoltaic cells having only PN heterojunction potential barriers
- H10F10/167—Photovoltaic cells having only PN heterojunction potential barriers comprising Group I-III-VI materials, e.g. CdS/CuInSe2 [CIS] heterojunction photovoltaic cells
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F71/00—Manufacture or treatment of devices covered by this subclass
- H10F71/125—The active layers comprising only Group II-VI materials, e.g. CdS, ZnS or CdTe
- H10F71/1257—The active layers comprising only Group II-VI materials, e.g. CdS, ZnS or CdTe comprising growth substrates not made of Group II-VI materials
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10F77/00—Constructional details of devices covered by this subclass
- H10F77/10—Semiconductor bodies
- H10F77/12—Active materials
- H10F77/123—Active materials comprising only Group II-VI materials, e.g. CdS, ZnS or HgCdTe
- H10F77/1233—Active materials comprising only Group II-VI materials, e.g. CdS, ZnS or HgCdTe characterised by the dopants
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/541—CuInSe2 material PV cells
Landscapes
- Photovoltaic Devices (AREA)
Abstract
METHODS FOR DEPOSITION OF LOW RESISTIVITY
SEMICONDUCTORS AND FABRICATION OF SOLAR CELLS
ABSTRACT OF THE DISCLOSURE
The present invention describes a method of deposit-ing low resistivity CdS, ZnS and ZnSe thin films for elec-tronic device applications. The CdS, ZnS or ZnSe films are deposited respectively from electrolytes containing ions of Cd and S, Zn and S, or Zn and Se. The resistivity of the deposited thin films is controlled by adding impurities in the electrolyte and carrying out co-deposition. A method for the fabrication of thin film solar cells using elec-trodeposition is also given.
SEMICONDUCTORS AND FABRICATION OF SOLAR CELLS
ABSTRACT OF THE DISCLOSURE
The present invention describes a method of deposit-ing low resistivity CdS, ZnS and ZnSe thin films for elec-tronic device applications. The CdS, ZnS or ZnSe films are deposited respectively from electrolytes containing ions of Cd and S, Zn and S, or Zn and Se. The resistivity of the deposited thin films is controlled by adding impurities in the electrolyte and carrying out co-deposition. A method for the fabrication of thin film solar cells using elec-trodeposition is also given.
Description
2093~1~7 BACKGIROIIND OF Tlll II~IVENTION
1. Field of the Invention The present invention re:Lates to method~ for the deposition of low resistivity CdS, ZnS and ZnSe thin films and methods for the fabrication o~E thin film solar cells.
1. Field of the Invention The present invention re:Lates to method~ for the deposition of low resistivity CdS, ZnS and ZnSe thin films and methods for the fabrication o~E thin film solar cells.
2. Description of the Prior Art In many electronic applications, it is required to prepare semiconductor thin ~ilms such as CdS, 2nS and ZnSe with a low electrical resistivity. This low resistivity i~
needed in order to improve performance of devices formed using these materials. Conventional preparation methods for CdS, ZnS and ZnSe include vacuum deposition, sputtering and chemical vapour deposition. For the *abrication of large area devices suck as 801ar cells and display units, it is pre~erable to deposit the thin ~ilms using a low cost method such as electrodeposition. The electrodeposition method xequire~ very small amount of energy as compared to conventional methods and has a very high material ukiliza tion rate.
2~ / 7 The electrodeposition method has been used by sever-al researchers to prepare CdS, ZnS and ZnSe thin films.
The method has been used by S.N. Qiu and I. Shih (Proce~d-ings of the 6th International Photovoltaic Science and Engineering Conference, Page 1011-1014, 1992~ to deposit CdS thin ~ilms. B.R. Sanders and A.H. Kitai (Journal of Crystal Growth, volume 100, pag~ 405 410, lg90) have re-ported the electrodepositon o~ ZnS thin ~ilms. Using the electrodeposition method, A. Darkowski and A. A. Grabowski (Solar Energy Materials, Volume 23, page 75-82, 1991) have reported results on th~ pr~paration of ZnSe thin ~ilms.
In all these experiments reported for the above semiconductors, the alectrical resistivity of the deposited CdS, ZnS or ZnSe i~ controlled by adjusting the film stoi-chiometry or not controlled at all. The resistivity is general large when the composition is not intentionally controlled due to the stoichiometry in the deposited filmsO For the films deposited with controlled stoichiome-try, the thermal stability of the resistivity often is poor especially when the films are ~ubjected to heat treatment, which is required for many electronic device fabrication.
Therefore, the CdS, ZnS and ZnSe films prepared by the electrodepositlon methods by previous art may not be suit-able for fabrication of devices (such as photo detectors and solar cells) which require low resistivity counter 2~3~07 electrodes. In Canadian patent No. 1,272,107 issued to S.N.
Qiu, C.X. Qiu and I. Shih, doping methods to reduce elec-trical resistivity of vacuum deposited semiconductors such as CdS, CdSO and ZnO have been described. The doped semi-conductors (~or example 1-2~ In in ZnO or 1-2% In in CdS) prepared by the vacuum method generally show a more stable thermal property as compared to the films without doping.
From the above comment, it is evident that there is a need to develop a method of introducing dopant and con-trolling its amount in the CdS, ZnS and ZnSe thin films prepared by the electrodeposition method.
C)BJECTS AIND ST~TEMENT OF THiE PRESEI`JT
INVEINTION
One object of this invention is to provide an elec-trodeposition method for khe deposition of low resistivity CdS, ~nS and ZnSe thin films.
Another object of this invention is to provide a method to control the amount of dopants in the electrode-posited CdS, ZnS and ZnSe thin filmsO
Yet another object of this invention is to provide a method to prepare a thin film solar cell by the electrodep-osit1on.
2 ~ 9 3 7 O i~
BRIIEF E~ SCP~IPT101`3 OF TIIE DRAWII`IGS
Fig. 1 is a schematic diagxam showing the electrodeposition apparatus for the CdS, ZnS or ZnSe thin ~ilms.
Fig. 2 is a cross-sectional view of a ZnSe/CdS/CuInSe2/~o solar cell.
2 ~ 9 3 r~ o DESCIF21PTIOIY OIF THE~ PIREIFERRED ENIBOl)l~RENTS
Referring now to the drawings, there is shown in Fig. 1, which illustrates the preferred system used in this invention, an electrolyte (1) which is contained in a glass container (2). The electrolyte contains ions or complex~s of Cd and S for the CdS deposition, Zn and Se for tha ZnSe deposition, and Zn and S for ZnS deposition . Ion source for dopants (such as Al, Ga or In) is then introduced into the electrolyte as dopants. A small amount o~ acid such as ~NO3, HCl, H~SO4 or other ion source such as A12C13 is also added to the electrolyte in order to increase the conduc-tivity~ A conducting anode (3) such as Pt or C is inserted through a top plate (4~ into the electrolyte. One end of the conducting anode is connected electrically to the positive terminal of a dc pow~r source (5). A substrate (6) such as Mo, CdTe coated Mo/glass or CuInSe2-coated Mo/glass is el~ctrically connected to the negative terminal of the dc power source (5).
To start the deposition o~ doped CdS, ZnS or ZnSe thin ~ilm, the substrate is inserted into the electrolyte ~1) and the power source (5) is turned on. For the deposi-tion using an electrolyte containing ions of Zn, Se and .~ .... ,. - , -.,.~.-,".," ~ "~ ,"~ ",~ "~"~" "~",~
~ o 9 ~ rl~ ~) 7 ions of ~n (for dopants), these ions will now be deposited on the substrate to form an In-doped ZnSe thin film (7).
For the deposition using an electrolyte containing ions of Zn, S and ions of In (for dopants), these .ions will be deposited on the substrate to ~orm an In-doped ZnS thin film~ For the deposition using an electrolyte containing ions of Cd, S and ions of In (for dopants), these ions will now be deposited on the substrate to form an In-doped ZnSe thin film.
In order to obtain a proper agitation of the elec-trolyte, a glass stirrer (8) is inserted into the electro-lyte and is allowed to rotate at a constant rate of about 30 rpm. A temperature sensor (9) is also inserted into the electrolyte to sense its temperature. The output of the temperature sensor is connected to a temperatura controller and power supply unit (10) which supply power to a resis-tive heater (11). The heater is used to heat the electro~
lyte to a specific temperature.
The method of electrodeposition of the doped low resistivity thin films of semiconductors such as CdS, ZnS
and ZnSe can be advantageously used to fabricated a hetero-junction solar cell. Re~erxing to Fig. ~, the fabrication starts from a glass substrate (12) with a thickness of 1 mm. A layer of Mo (13~ with a thickness of 1 ~m is sput-2~9~J~
tered on the glai~s for back electrical contact. A layer ofp-type CuInSe2 (14~ with a thickness of 1.5 ~m is then electrodeposited ~rom an electrolyte containing ion~ and complexes of Cu, In and Se. After the deposition, the CuInSe2 is heat treated at about 350C in vacuum ~or 20 minutes to improve the crystallinity and the electrical properties. This is followed by coating of a t~in layer (100-200 A thick) of high resistivity CdS (15) either by electrodeposition or dipping in a solution containing ions and complexes of Cd and S. Following this, a layar of low resistivity and doped CdS, ZnS or ZnSe (16) is deposited by the electrodeposition method ~escribed in Fig. 1. Grids of metals such as Al with a thickness of 2 ~m are ~inally deposited by vacuum evaporation to complete the solar cell ~abrication.
one example o~ the electrolyte used for the deposi-tion o~ In-doped ZnSe thin films is given below. The elec trolyte consists of 260 g ZnS04-7H20, 65 mg Se2, 100 mg In2(S04)3 and 900 cc H20. The large ratio between the ZnS0~ and SeO2 is required in order to obtain approximately equal deposition rate for Zn and Se, which have different deposition potentialsO The stoichiometry and deposition rate o~ the In-doped ZnSe thin ~ilm is determined by the ion concentration o~ the electrolyte, the stirring rate, temperature and the deposition potential supplied between 2~7~7 the substrate and the Pt anode. For example, for the films deposited at low potential, Se-rich materials are formed.
Therefore, it is important to control the deposition poten-tial to a value of about 3 volts for the above composition~
Furthermore, the electrolyte temperature will have to be controlled to a constant value during the deposition. Using the electrolyte composition given above, smooth In-doped ZnSe films with a thicknsss of 1 ~m was deposited at a temperature of 55C. Although the temperature can be varied over a range, the electrolyte concentration and deposition potential will have to be changed in order to deposit stoichiometric and uniform ZnSe films. The deposition rate o~ In doped ZnSe using the electrolyte given in the above example is about 80 A/minute. The deposited films are smooth and the electrical resistivity is about 10 3 ohm-cmO
Results o~ energy di~persive X ray analysis (EDX) show that the In content in the deposited ZnSe films is about 2%.
This value is roughly e~ual to the concectration of impuri-ties required to reduced resistivity in the vacuum deposit-ed thin ~ilms. The resistivity value in the electrodeposit-ed ZnSe films is low enough for the fabrication electronic devices, such as photo detectors and solar cells.
! One example of the eleotrodeposition for the fabri-cation of a solid state junction solar cell is presented below. A ~aysr of p-type CuInSe2 with a thickness of 1.5 ~m ~: ', , ' ! l i . ' 2~93707 is deposited on a Mo-coated glas~ substrate (thickness of the Mo layer is 1 ~m) by an electrodeposition method (C.X.
Qiu and I. Shih, Canadian Journal of Physics, volume 65, page 1011, 1987 or C.X. Qiu and I. Shih, Phosphorus and Sulfur, volume 38, page 409-417, 1988). The deposited CuInSe2 is suhjected to a heat tr,eatment in vacuum at 350C
for 20 minutes to produce material with an acceptor concen-tration of 1016 cm 3. A layer of high resistivity CdS
(~hickness about 100-20~ A) is then coated on the CuInSe2 by electrodeposition or by a dipping method. For the dip-ping method, the CuInSe2 is immersed in a sclution of 100 mg CdC12, 310 mg NH4Cl, 100 mg NH2CSNH2 and 70 cc H20 at 65GC for about 10 minutes. After the deposition o~ the thin high resistivity CdS layer, a layer of low resistivity In-doped ZnSe (thickness about 1 ~m~ is electrodeposited using the following method. The electrolyte used for the deposi tion of In-doped ZnSe thin films i5 given below. The elec-trolyte consists of 260 g ZnS04-7H20, 65 mg Se2, 100 mg In2(S0~)3 and 900 cc H20 The large ratio between the ZnS04 and SeO2 is re~uired in order to obtain approximately equal deposition rate for Zn and Se, which have different deposition potentials. The stoichiometry and deposition rate of the In-doped ZnSe thin film is determined by the ion concentration of the electrolyte, the stirring rate, temperature and the deposition potential supplied between the CuInSe2-coated substrate and the Pt anode. For example, 2 ~ 9 3 7 0 ~
for the films deposited at low potential, Se-rich materials are formed. Thereforel it is :important to control the deposition potential to a value of about 3 volts for the above composition~ Furthermore, th~ electrolyte temperature will have to be controlled to a constant value during the deposition. Using the electrolyte composition given above, smooth In-doped ZnSe films with a thickness sf l ~m was deposited at a temperature of 55C. Although the tempera-ture can be varied over a range, the electrolyte concentra-tion and deposition potential will have to be changed in order to deposit stoichiometric and uniform ZnSe films. The deposition rate of In doped ZnSe using the electrolyte given in the above example is about 80 A/minute. After the deposition of the low resistivity ZnSe film, metal counter electrodes (such as Al) ar~ evaporated on the ZnSe surface to form solar cells.
.
needed in order to improve performance of devices formed using these materials. Conventional preparation methods for CdS, ZnS and ZnSe include vacuum deposition, sputtering and chemical vapour deposition. For the *abrication of large area devices suck as 801ar cells and display units, it is pre~erable to deposit the thin ~ilms using a low cost method such as electrodeposition. The electrodeposition method xequire~ very small amount of energy as compared to conventional methods and has a very high material ukiliza tion rate.
2~ / 7 The electrodeposition method has been used by sever-al researchers to prepare CdS, ZnS and ZnSe thin films.
The method has been used by S.N. Qiu and I. Shih (Proce~d-ings of the 6th International Photovoltaic Science and Engineering Conference, Page 1011-1014, 1992~ to deposit CdS thin ~ilms. B.R. Sanders and A.H. Kitai (Journal of Crystal Growth, volume 100, pag~ 405 410, lg90) have re-ported the electrodepositon o~ ZnS thin ~ilms. Using the electrodeposition method, A. Darkowski and A. A. Grabowski (Solar Energy Materials, Volume 23, page 75-82, 1991) have reported results on th~ pr~paration of ZnSe thin ~ilms.
In all these experiments reported for the above semiconductors, the alectrical resistivity of the deposited CdS, ZnS or ZnSe i~ controlled by adjusting the film stoi-chiometry or not controlled at all. The resistivity is general large when the composition is not intentionally controlled due to the stoichiometry in the deposited filmsO For the films deposited with controlled stoichiome-try, the thermal stability of the resistivity often is poor especially when the films are ~ubjected to heat treatment, which is required for many electronic device fabrication.
Therefore, the CdS, ZnS and ZnSe films prepared by the electrodepositlon methods by previous art may not be suit-able for fabrication of devices (such as photo detectors and solar cells) which require low resistivity counter 2~3~07 electrodes. In Canadian patent No. 1,272,107 issued to S.N.
Qiu, C.X. Qiu and I. Shih, doping methods to reduce elec-trical resistivity of vacuum deposited semiconductors such as CdS, CdSO and ZnO have been described. The doped semi-conductors (~or example 1-2~ In in ZnO or 1-2% In in CdS) prepared by the vacuum method generally show a more stable thermal property as compared to the films without doping.
From the above comment, it is evident that there is a need to develop a method of introducing dopant and con-trolling its amount in the CdS, ZnS and ZnSe thin films prepared by the electrodeposition method.
C)BJECTS AIND ST~TEMENT OF THiE PRESEI`JT
INVEINTION
One object of this invention is to provide an elec-trodeposition method for khe deposition of low resistivity CdS, ~nS and ZnSe thin films.
Another object of this invention is to provide a method to control the amount of dopants in the electrode-posited CdS, ZnS and ZnSe thin filmsO
Yet another object of this invention is to provide a method to prepare a thin film solar cell by the electrodep-osit1on.
2 ~ 9 3 7 O i~
BRIIEF E~ SCP~IPT101`3 OF TIIE DRAWII`IGS
Fig. 1 is a schematic diagxam showing the electrodeposition apparatus for the CdS, ZnS or ZnSe thin ~ilms.
Fig. 2 is a cross-sectional view of a ZnSe/CdS/CuInSe2/~o solar cell.
2 ~ 9 3 r~ o DESCIF21PTIOIY OIF THE~ PIREIFERRED ENIBOl)l~RENTS
Referring now to the drawings, there is shown in Fig. 1, which illustrates the preferred system used in this invention, an electrolyte (1) which is contained in a glass container (2). The electrolyte contains ions or complex~s of Cd and S for the CdS deposition, Zn and Se for tha ZnSe deposition, and Zn and S for ZnS deposition . Ion source for dopants (such as Al, Ga or In) is then introduced into the electrolyte as dopants. A small amount o~ acid such as ~NO3, HCl, H~SO4 or other ion source such as A12C13 is also added to the electrolyte in order to increase the conduc-tivity~ A conducting anode (3) such as Pt or C is inserted through a top plate (4~ into the electrolyte. One end of the conducting anode is connected electrically to the positive terminal of a dc pow~r source (5). A substrate (6) such as Mo, CdTe coated Mo/glass or CuInSe2-coated Mo/glass is el~ctrically connected to the negative terminal of the dc power source (5).
To start the deposition o~ doped CdS, ZnS or ZnSe thin ~ilm, the substrate is inserted into the electrolyte ~1) and the power source (5) is turned on. For the deposi-tion using an electrolyte containing ions of Zn, Se and .~ .... ,. - , -.,.~.-,".," ~ "~ ,"~ ",~ "~"~" "~",~
~ o 9 ~ rl~ ~) 7 ions of ~n (for dopants), these ions will now be deposited on the substrate to form an In-doped ZnSe thin film (7).
For the deposition using an electrolyte containing ions of Zn, S and ions of In (for dopants), these .ions will be deposited on the substrate to ~orm an In-doped ZnS thin film~ For the deposition using an electrolyte containing ions of Cd, S and ions of In (for dopants), these ions will now be deposited on the substrate to form an In-doped ZnSe thin film.
In order to obtain a proper agitation of the elec-trolyte, a glass stirrer (8) is inserted into the electro-lyte and is allowed to rotate at a constant rate of about 30 rpm. A temperature sensor (9) is also inserted into the electrolyte to sense its temperature. The output of the temperature sensor is connected to a temperatura controller and power supply unit (10) which supply power to a resis-tive heater (11). The heater is used to heat the electro~
lyte to a specific temperature.
The method of electrodeposition of the doped low resistivity thin films of semiconductors such as CdS, ZnS
and ZnSe can be advantageously used to fabricated a hetero-junction solar cell. Re~erxing to Fig. ~, the fabrication starts from a glass substrate (12) with a thickness of 1 mm. A layer of Mo (13~ with a thickness of 1 ~m is sput-2~9~J~
tered on the glai~s for back electrical contact. A layer ofp-type CuInSe2 (14~ with a thickness of 1.5 ~m is then electrodeposited ~rom an electrolyte containing ion~ and complexes of Cu, In and Se. After the deposition, the CuInSe2 is heat treated at about 350C in vacuum ~or 20 minutes to improve the crystallinity and the electrical properties. This is followed by coating of a t~in layer (100-200 A thick) of high resistivity CdS (15) either by electrodeposition or dipping in a solution containing ions and complexes of Cd and S. Following this, a layar of low resistivity and doped CdS, ZnS or ZnSe (16) is deposited by the electrodeposition method ~escribed in Fig. 1. Grids of metals such as Al with a thickness of 2 ~m are ~inally deposited by vacuum evaporation to complete the solar cell ~abrication.
one example o~ the electrolyte used for the deposi-tion o~ In-doped ZnSe thin films is given below. The elec trolyte consists of 260 g ZnS04-7H20, 65 mg Se2, 100 mg In2(S04)3 and 900 cc H20. The large ratio between the ZnS0~ and SeO2 is required in order to obtain approximately equal deposition rate for Zn and Se, which have different deposition potentialsO The stoichiometry and deposition rate o~ the In-doped ZnSe thin ~ilm is determined by the ion concentration o~ the electrolyte, the stirring rate, temperature and the deposition potential supplied between 2~7~7 the substrate and the Pt anode. For example, for the films deposited at low potential, Se-rich materials are formed.
Therefore, it is important to control the deposition poten-tial to a value of about 3 volts for the above composition~
Furthermore, the electrolyte temperature will have to be controlled to a constant value during the deposition. Using the electrolyte composition given above, smooth In-doped ZnSe films with a thicknsss of 1 ~m was deposited at a temperature of 55C. Although the temperature can be varied over a range, the electrolyte concentration and deposition potential will have to be changed in order to deposit stoichiometric and uniform ZnSe films. The deposition rate o~ In doped ZnSe using the electrolyte given in the above example is about 80 A/minute. The deposited films are smooth and the electrical resistivity is about 10 3 ohm-cmO
Results o~ energy di~persive X ray analysis (EDX) show that the In content in the deposited ZnSe films is about 2%.
This value is roughly e~ual to the concectration of impuri-ties required to reduced resistivity in the vacuum deposit-ed thin ~ilms. The resistivity value in the electrodeposit-ed ZnSe films is low enough for the fabrication electronic devices, such as photo detectors and solar cells.
! One example of the eleotrodeposition for the fabri-cation of a solid state junction solar cell is presented below. A ~aysr of p-type CuInSe2 with a thickness of 1.5 ~m ~: ', , ' ! l i . ' 2~93707 is deposited on a Mo-coated glas~ substrate (thickness of the Mo layer is 1 ~m) by an electrodeposition method (C.X.
Qiu and I. Shih, Canadian Journal of Physics, volume 65, page 1011, 1987 or C.X. Qiu and I. Shih, Phosphorus and Sulfur, volume 38, page 409-417, 1988). The deposited CuInSe2 is suhjected to a heat tr,eatment in vacuum at 350C
for 20 minutes to produce material with an acceptor concen-tration of 1016 cm 3. A layer of high resistivity CdS
(~hickness about 100-20~ A) is then coated on the CuInSe2 by electrodeposition or by a dipping method. For the dip-ping method, the CuInSe2 is immersed in a sclution of 100 mg CdC12, 310 mg NH4Cl, 100 mg NH2CSNH2 and 70 cc H20 at 65GC for about 10 minutes. After the deposition o~ the thin high resistivity CdS layer, a layer of low resistivity In-doped ZnSe (thickness about 1 ~m~ is electrodeposited using the following method. The electrolyte used for the deposi tion of In-doped ZnSe thin films i5 given below. The elec-trolyte consists of 260 g ZnS04-7H20, 65 mg Se2, 100 mg In2(S0~)3 and 900 cc H20 The large ratio between the ZnS04 and SeO2 is re~uired in order to obtain approximately equal deposition rate for Zn and Se, which have different deposition potentials. The stoichiometry and deposition rate of the In-doped ZnSe thin film is determined by the ion concentration of the electrolyte, the stirring rate, temperature and the deposition potential supplied between the CuInSe2-coated substrate and the Pt anode. For example, 2 ~ 9 3 7 0 ~
for the films deposited at low potential, Se-rich materials are formed. Thereforel it is :important to control the deposition potential to a value of about 3 volts for the above composition~ Furthermore, th~ electrolyte temperature will have to be controlled to a constant value during the deposition. Using the electrolyte composition given above, smooth In-doped ZnSe films with a thickness sf l ~m was deposited at a temperature of 55C. Although the tempera-ture can be varied over a range, the electrolyte concentra-tion and deposition potential will have to be changed in order to deposit stoichiometric and uniform ZnSe films. The deposition rate of In doped ZnSe using the electrolyte given in the above example is about 80 A/minute. After the deposition of the low resistivity ZnSe film, metal counter electrodes (such as Al) ar~ evaporated on the ZnSe surface to form solar cells.
.
Claims (16)
1. A method for preparation of low resistivity semiconduc-tor thin films comprising:
(A) introducing ion sources in water for said semicon-ductor to form an electrolyte, (B) introducing an ion source into said electrolyte for dopant, (C) inserting an anode and a substrate into said electrolyte, (D) applying a electrical source between said anode and said substrate to supply a voltage and a current to deposit a layer of said semiconductor on said substrate.
(A) introducing ion sources in water for said semicon-ductor to form an electrolyte, (B) introducing an ion source into said electrolyte for dopant, (C) inserting an anode and a substrate into said electrolyte, (D) applying a electrical source between said anode and said substrate to supply a voltage and a current to deposit a layer of said semiconductor on said substrate.
2. A method for preparation of low resistivity semiconduc-tor according to claim 1, wherein said resistivity is controlled by controlling amount of said dopant introduced in said semiconductor. Said amount of dopant in said semi-conductor is controlled by controlling amount of said ion source of dopant in said electrolyte.
3. A method for preparation of low resistivity semiconduc-tor according to claim 2, further comprising a step of controlling amount of said dopant in said semiconductor by controlling current and voltage supplied by said power source.
4. A method for preparation of low resistivity semiconduc-tor according to claim 1, wherein said power source is a dc power supply.
5. A method for preparation of low resistivity semiconduc-tor according to claim 1, wherein said semiconductor is selected from a group of CdS, ZnSe and ZnS.
6. A method for preparation of low resistivity semiconduc-tor according to claim 1, wherein said dopant is selected from a group of Al, Ga and In.
7. A method for preparation of low resistivity semiconduc-tor according to claim 1 and claim 2, wherein said semicon-ductor is n-type.
8. A method for fabrication of thin film solar cells comprising:
(A) introducing ion sources in water for said semicon-ductor to form an electrolyte, (B) introducing an ion source into said electrolyte for dopant, (C) inserting an anode and a substrate into said electrolyte, (D) applying a electrical source between said anode and said substrate to supply a voltage and a current to deposit a layer of said semiconductor on said substrate.
(A) introducing ion sources in water for said semicon-ductor to form an electrolyte, (B) introducing an ion source into said electrolyte for dopant, (C) inserting an anode and a substrate into said electrolyte, (D) applying a electrical source between said anode and said substrate to supply a voltage and a current to deposit a layer of said semiconductor on said substrate.
9. A method for the fabrication of solar cells according to claim 8, wherein said substrate comprises a metal coated with a layer of absorbing semiconductor.
10. A method for the fabrication of solar cells according to claim 8 and claim 9, wherein said absorbing semiconduc-tor is chosen from a group of CdTe and CuInSe2.
11. A method for fabrication of solar cells according to claim 8, wherein said resistivity of said semiconductor is controlled by controlling amount of said dopant introduced in said semiconductor. Said amount of dopant in said semi-conductor is controlled by controlling amount of said ion source of dopant in said electrolyte.
12. A method for fabrication of solar cells according to claim 8, further comprising a step of controlling amount of said dopant in said semiconductor by controlling current and voltage supplied by said power source.
13. A method for fabrication of solar cells according to claim 8, wherein said power source is a dc power supply.
14. A method for fabrication of solar cells according to claim 8, wherein said semiconductor is n-type and isselect-ed from a group of CdS, ZnSe and ZnS.
15. A method for fabrication of solar cells according to claim 8, wherein said dopant is selected from a group of Al, Ga and In.
16. A method for the fabrication of solar cells according to claim 8 and claim 9, wherein at least part of said absorbing semiconductor is p-type.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CA002093707A CA2093707A1 (en) | 1993-04-08 | 1993-04-08 | Methods for deposition of low resistivity semiconductors and fabrication of solar cells |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002093707A CA2093707A1 (en) | 1993-04-08 | 1993-04-08 | Methods for deposition of low resistivity semiconductors and fabrication of solar cells |
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| Publication Number | Publication Date |
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| CA2093707A1 true CA2093707A1 (en) | 1994-10-09 |
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|---|---|---|---|
| CA002093707A Abandoned CA2093707A1 (en) | 1993-04-08 | 1993-04-08 | Methods for deposition of low resistivity semiconductors and fabrication of solar cells |
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| CA (1) | CA2093707A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101980366A (en) * | 2010-09-27 | 2011-02-23 | 深圳丹邦投资集团有限公司 | Buffer layer of flexible thin film solar cell and preparation method thereof |
| CN112221518A (en) * | 2020-10-21 | 2021-01-15 | 广东工业大学 | CdS/MoSxComposite material and one-step electrochemical deposition preparation method and application thereof |
-
1993
- 1993-04-08 CA CA002093707A patent/CA2093707A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101980366A (en) * | 2010-09-27 | 2011-02-23 | 深圳丹邦投资集团有限公司 | Buffer layer of flexible thin film solar cell and preparation method thereof |
| CN101980366B (en) * | 2010-09-27 | 2012-10-17 | 深圳丹邦投资集团有限公司 | Buffer layer of flexible thin film solar cell and preparation method thereof |
| CN112221518A (en) * | 2020-10-21 | 2021-01-15 | 广东工业大学 | CdS/MoSxComposite material and one-step electrochemical deposition preparation method and application thereof |
| CN112221518B (en) * | 2020-10-21 | 2021-12-24 | 广东工业大学 | A kind of CdS/MoSx composite material and its one-step electrochemical deposition preparation method and application |
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