Microstructure and Properties of Cadmium Sulfide Thin Films Prepared by Chemical Bath Deposition

Abstract

Abstract: CdS thin films for the buffer layer of Cu(In,Ga)Se₂ solar cells were prepared by chemical bath deposition at different ammonia dosages. The initial concentration, pH value and ion product of the reaction particles in the mixed solution were calculated according to the chemical equilibrium kinetics. The film thickness, surface morphology, crystal structure, external quantum efficiency and photoelectric conversion efficiency of the samples were analyzed by step tester, SEM, XRD, EQE and IV tester. The results show that with the increase of ammonia amount, the homogeneous reaction rate reduces because the free Cd²⁺ concentration decreases, and the heterogeneous reaction rate increases because the Cd(OH)₂(NH₃)_n density adsorbed on the substrate surface increases; the crystal structure of CdS thin films changes from cubic phase to hexagonal phase because the cubic phase is formed by the homogeneous reaction, and the hexagonal CdS thin film is formed by the heterogeneous reaction; the surface morphology changes from loose porous structure formed by physical adsorption of large round particles to uniform and dense thin film grown by liquid phase epitaxy, the grain shape changes from willow catkins to granular, the grain size gradually increases, the particle size distribution is more uniform, and the film surface is smoother; the electrical parameters such as EQE, V_oc,J_sc, FF and R_s are optimized, and the photoelectric conversion efficiency increases from 7.64% to 13.60%.

Key words: CdS thin film, chemical bath deposition, equilibrium kinetic, crystallization type, CIGS

CLC Number:

ZHANG Xiaoyong, ZHANG Yanchun, ZHANG Xiaoyu, ZHANG Sen. Microstructure and Properties of Cadmium Sulfide Thin Films Prepared by Chemical Bath Deposition[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2021, 50(2): 310-317.

References

[1] SHEN H P, DUONG T, PENG J, et al. Mechanically-stacked perovskite/CIGS tandem solar cells with efficiency of 23.9% and reduced oxygen sensitivity[J]. Energy & Environmental Science, 2018, 11(2): 394-406.
[2] MINEMOTO T, MATSUI T, TAKAKURA H, et al. Theoretical analysis of the effect of conduction band offset of window/CIS layers on performance of CIS solar cells using device simulation[J]. Solar Energy Materials and Solar Cells, 2001, 67(1/2/3/4): 83-88.
[3] XUE Y M, SUN Y, HE Q, et al. Structural characteristic of CdS thin films and their influences on Cu(In, Ga)Se₂(CIGS) thin film solar cells[J]. Chinese Journal of Semiconductors, 2005, 26(2): 225-229.
[4] RAU U, SCHOCK H W. Cu(In, Ga)Se₂ thin-film solar cells[M]//Solar Cells. Amsterdam: Elsevier, 2013: 261-304.
[5] LEI B, HOU W W, LI S H, et al. Cadmium ion soaking treatment for solution processed CuInS_xSe_2-x solar cells and its effect on defect properties[J]. Solar Energy Materials and Solar Cells, 2011, 95(8): 2384-2389.
[6] FERNANDO D, KHAN M, VASQUEZ Y. Control of the crystalline phase and morphology of CdS deposited on microstructured surfaces by chemical bath deposition[J]. Materials Science in Semiconductor Processing, 2015, 30: 174-180.
[7] GHALI M, EISSA A M, MOSAAD M M. Crystalline phase transformation of colloidal cadmium sulfide nanocrystals[J]. International Journal of Modern Physics B, 2017, 31(6): 1750037.
[8] YÜCEL E, ŞAHIN O. Effect of pH on the structural, optical and nanomechanical properties of CdS thin films grown by chemical bath deposition[J]. Ceramics International, 2016, 42(5): 6399-6407.
[9] ZHANG L Q, JIANG J C, WANG W, et al. Growth process and properties of CdS thin films prepared by chemical bath deposition at different pH values[J]. Journal of Materials Science: Materials in Electronics, 2018, 29(9): 7637-7643.
[10] WILSON K C, BASHEER AHAMED M. Influence of bath temperature on surface modification and optoelectronic properties of chemical bath deposited CdS thin film nanostructures[J]. Materials Science and Engineering: B, 2019, 251: 114444.
[11] HARIECH S, AIDA M S, BOUGDIRA J, et al. Cadmium sulfide thin films growth by chemical bath deposition[J]. Journal of Semiconductors, 2018, 39(3): 034004.
[12] GÖDE F, üNLü S. Synthesis and characterization of CdS window layers for PbS thin film solar cells[J]. Materials Science in Semiconductor Processing, 2019, 90: 92-100.
[13] VILCHIS H, CONDE J, SANTIS J A, et al. Influence of III-V substrates on the texture, structural, and optical properties of CdS thin films deposited by chemical bath deposition[J]. Journal of Materials Science: Materials in Electronics, 2020, 31(5): 4170-4177.
[14] MOUALKIA H, REKHILA G, MAHDJOUB A, et al. The semiconducting properties of CdS nanocrystalline thin films prepared by chemical bath deposition. Application to the eosin photodegradation[J]. Journal of Materials Science: Materials in Electronics, 2017, 28(24): 19105-19112.
[15] WALDIYA M, NARASIMMAN R, BHAGAT D, et al. Nanoparticulate CdS 2D array by chemical bath deposition: characterization and optoelectronic study[J]. Materials Chemistry and Physics, 2019, 226: 26-33.
[16] MAGHOULI M, ESHGHI H. Effect of deposition time on physical properties of nanostructured CdS thin films grown by chemical bath deposition technique[J]. Superlattices and Microstructures, 2019, 128: 327-333.
[17] OUAFI M, JABER B, ATOURKI L, et al. In situ low-temperature chemical bath deposition of CdS thin films without thickness limitation: structural and optical properties[J]. International Journal of Photoenergy, 2018, 2018: 1-12.
[18] ASHOK A, REGMI G, ROMERO-NU＇ÑEZ A, et al. Comparative studies of CdS thin films by chemical bath deposition techniques as a buffer layer for solar cell applications[J]. Journal of Materials Science: Materials in Electronics, 2020, 31(10): 7499-7518.
[19] SLONOPAS A, RYAN H, FOLEY B, et al. Growth mechanisms and their effects on the opto-electrical properties of CdS thin films prepared by chemical bath deposition[J]. Materials Science in Semiconductor Processing, 2016, 52: 24-31.
[20] DOÑA J M, HERRERO J. Chemical bath deposition of CdS thin films: an approach to the chemical mechanism through study of the film microstructure[J]. Journal of the Electrochemical Society, 1997, 144(11): 4081-4091.
[21] MARTiNEZ M A, GUILLéN C, HERRERO J. Morphological and structural studies of CBD-CdS thin films by microscopy and diffraction techniques[J]. Applied Surface Science, 1998, 136(1/2): 8-16.
[22] HODES G. Semiconductor and ceramic nanoparticle films deposited by chemical bath deposition[J]. Physical Chemistry Chemical Physics, 2007, 9(18): 2181-2196.
[23] FROMENT M, LINCOT D. Phase formation processes in solution at the atomic level: metal chalcogenide semiconductors[J]. Electrochimica Acta, 1995, 40(10): 1293-1303.
[24] ORTEGA-BORGES R, LINCOT D. Mechanism of chemical bath deposition of cadmium sulfide thin films in the ammonia-thiourea system: in situ kinetic study and modelization[J]. Journal of the Electrochemical Society, 1993, 140(12): 3464-3473.
[25] O′BRIEN P, MCALEESE J. Developing an understanding of the processes controlling the chemical bath deposition of ZnS and CdS[J]. Journal of Materials Chemistry, 1998, 8(11): 2309-2314.
[26] BALLIPINAR F, KITAMURA N, NANDUR A, et al. Cadmium oxysulfide Cd(S, O) as novel high transmittance buffer layer formed by surfactant mediated chemical bath deposition for thin-film heterojunction solar cells[J]. MRS Advances, 2016, 1(41): 2833-2838.
[27] GARZA-HERNáNDEZ R, CARRILLO-CASTILLO A, MARTíNEZ-LANDEROS V H, et al. In-situ X-ray photoelectron spectroscopy analysis of the initial growth of CdS thin films by chemical bath deposition[J]. Thin Solid Films, 2019, 682: 142-146.
[28] NAKADA T. Nano-structural investigations on Cd-doping into Cu(In, Ga)Se₂ thin films by chemical bath deposition process[J]. Thin Solid Films, 2000, 361/362: 346-352.
[29] JIANG C S, HASOON F S, MOUTINHO H R, et al. Direct evidence of a buried homojunction in Cu(In, Ga)Se₂ solar cells[J]. Applied Physics Letters, 2003, 82(1): 127-129.
[30] LU Z B, JIN R R, LIU Y, et al. Optimization of chemical bath deposited cadmium sulfide buffer layer for high-efficient CIGS thin film solar cells[J]. Materials Letters, 2017, 204: 53-56.
[31] LIU H Y, SOM S, SUNG J C, et al. Effects of ammonia concentration on the formation of CdS fabricated via microwave-assisted chemical bath deposition[J]. Journal of the American Ceramic Society, 2017, 100(11): 5120-5130.