Journal of Applied Science and Engineering

Published by Tamkang University Press


Impact Factor



Hong Zhang 1,2, Shuying Cheng This email address is being protected from spambots. You need JavaScript enabled to view it.1,2, Jinling Yu1,2, Yunfeng Lai1,2, Haifang Zhou1,2, Qiao Zheng1,2 and Hongjie Jia1,2

1College of Physics and Information Engineering, and Institute of Micro-Nano Devices and Solar Cells, Fuzhou University, Fuzhou, 350108, P.R. China
2Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Changzhou, 213164, P.R. China


Received: April 20, 2016
Accepted: September 5, 2016
Publication Date: March 1, 2017

Download Citation: ||  


Zn(O,S) is a promising alternative buffer layer to CdS in Cu2ZnSnS4 (CZTS) based solar cell due to its large bandgap and nontoxic elements. In this study the performance of CZTS/Zn(O,S)/ Al:ZnO solar cell was numerically simulated by Solar Cell Capacitance Simulator (SCAPS). And the sulfur content of Zn(O,S) buffer layer was varied to investigate how the chemical composition of Zn(O,S) influences the conduction band offsets at absorber/buffer and buffer/window interfaces and then affects the cell performance. It was found that the conduction-band offset (CBO) of the CZTS/Zn(O,S) heterojunction played a significant role in the performance of the solar cell. The electron affinity and bandgap of Zn(O,S) are controlled by the sulfur-to-oxygen ratios, and the resulting offset span is from +0.7 eV in the “spike” direction to -0.1 eV in the “cliff” direction if the electron affinity of CZTS is considered as 4.5 eV. When S/(S+O) atomic ratio of Zn(O,S) is about 0.3, the cell has a high conversion efficiency of 14.90% with CBO of 0.2 eV. The simulation results will provide some important guidelines for fabricating high efficient CZTS solar cells.

Keywords: CZTS, Zn(O,S), SCAPS


  1. [1] Dadlani, A. L., Trejo, O., Acharya, S., Torgersen, J., Petousis, I., Nordlund, D., Sarangi, R., Schindler, P. and Prinz, F. B., “Exploring the Local Electronic Structure and Geometric Arrangement of ALD Zn(O,S) Buffer Layers Using X-ray Absorption Spectroscopy,” Journal of Materials Chemistry C, Vol. 3, No. 47, pp. 1219212198 (2015). doi: 10.1039/C5TC02912K
  2. [2] Persson, C., Platzer-Björkman, C., Malmström, J., Törndahl, T. and Edoff, M., “Strong Valence-band Offset Bowing of ZnO1xSx Enhances p-type Nitrogen Doping of ZnO-like Alloys,” Physical Review Letters, Vol. 97, No. 14, p. 146403 (2006). doi: 10.1103/Phys RevLett.97.146403
  3. [3] Barkhouse, D. A. R., Haight, R., Sakai, N., Hiroi, H., Sugimoto, H. and Mitzi, D. B., “Cd-free Buffer Layer Materials on Cu2ZnSn(SxSe1x)4: Band Alignments with ZnO, ZnS and In2S3,” Applied Physics Letters, Vol. 100, No. 19, p. 193904 (2012). doi: 10.1063/1.4714737
  4. [4] Htay, M. T., Hashimoto, Y., Momose, N., Sasaki, K., Ishiguchi, H., Igarashi, S., Sakurai, K. and Ito, K., “A Cadmium-free Cu2ZnSnS4/ZnO Hetrojunction Solar Cell Prepared by Practicable Processes,” Japanese Journal of Applied Physics, Vol. 50, No. 3R, p. 032301 (2011). doi: 10.7567/JJAP.50.032301
  5. [5] Hones, C., Fuchs, A., Zweigart, S. and Siebentritt, S.,“Improved Chemically Deposited Zn(O,S) Buffers for Cu(In, Ga)(S, Se)2 Solar Cells by Controlled Incorporation of Indium,” Photovoltaics, IEEE Journal of, Vol. 6, No. 1, pp. 319325 (2016). doi: 10.1109/JPHO TOV.2015.2487818
  6. [6] Xu, J., Yang, Y., Cao, Z. and Xie, Z., “Preparations of Cu2ZnSnS4 Thin Films and Cu2ZnSnS4/Si Heterojunctions on Silicon Substrates by Sputtering,” Optik-International Journal for Light and Electron Optics, Vol. 127, No. 4, pp. 15671571 (2016). doi: 10.1016/j.ijleo. 2015.11.048
  7. [7] Ericson, T., Scragg, J. J., Hultqvist, A., Watjen, J. T., Szaniawski, P., Torndahl, T. and Platzer-Bjorkman, C., “Zn(O,S) Buffer Layers and Thickness Variations of CdS Buffer for Cu2ZnSnS4 Solar Cells,” Photovoltaics, IEEE Journal of, Vol. 4, No. 1, pp. 465469 (2014). doi: 10.1109/JPHOTOV.2013.2283058
  8. [8] Burgelman, M., Nollet, P. and Degrave, S., “Modelling Polycrystalline Semiconductor Solar Cells,” Thin Solid Films, Vol. 361, pp. 527532 (2000). doi: 10.1016/ S0040-6090(99)00825-1
  9. [9] Verschraegen, J. and Burgelman, M., “Numerical Modeling of Intra-band Tunneling for Heterojunction Solar Cells in SCAPS,” Thin Solid Films, Vol. 515, No. 15, pp. 62766279 (2007). doi: 10.1016/j.tsf.2006.12. 049
  10. [10] Movla, H., “Optimization of the CIGS Based Thin Film Solar Cells: Numerical Simulation and Analysis,” Optik-International Journal for Light and Electron Optics, Vol. 125, No. 1, pp. 6770 (2014). doi: 10. 1016/j.ijleo.2013.06.034
  11. [11] Simya, O. K., Mahaboobbatcha, A. and Balachander, K., “A Comparative Study on the Performance of Kesterite Based Thin Film Solar Cells Using SCAPS Simulation Program,” Superlattices and Microstructures, Vol. 82, pp. 248261 (2015). doi: 10.1016/j.spmi.2015. 02.020
  12. [12] Burgelman, M., Decock, K., Khelifi, S. and Abass, A., “Advanced Electrical Simulation of Thin Film Solar Cells,” Thin Solid Films, Vol. 535, pp. 296301 (2013). doi: 10.1016/j.tsf.2012.10.032
  13. [13] Frisk, C., Ericson, T., Li, S. Y., Szaniawski, P., Olsson, J. and Platzer-Björkman, C., “Combining Strong Interface Recombination with Bandgap Narrowing and Short Diffusion Length in Cu2ZnSnS4 Device Modeling,” Solar Energy Materials and Solar Cells, Vol. 144, pp. 364370 (2016). doi: 10.1016/j.solmat.2015. 09.019
  14. [14] Patel, M. and Ray, A., “Enhancement of Output Performance of Cu2ZnSnS4 Thin Film Solar Cells A Numerical Simulation Approach and Comparison to Experiments,” Physica B: Condensed Matter, Vol. 407, No. 21, pp. 43914397 (2012). doi: 10.1016/j.physb. 2012.07.042
  15. [15] Hsieh, T. M., Lue, S. J., Ao, J., Sun, Y., Feng, W. S. and Chang, L. B., “Characterizations of Chemical Bath- deposited Zinc Oxysulfide Films and the Effects of their Annealing on Copper-indium-gallium-selenide Solar Cell Efficiency,” Journal of Power Sources, Vol. 246, pp. 443448 (2014). doi: 10.1016/j.jpowsour.2013. 07.090
  16. [16] Buffière, M., Harel, S., Guillot-Deudon, C., Arzel, L., Barreau, N. and Kessler, J., “Effect of the Chemical Composition of Co-sputtered Zn(O,S) Buffer Layers on Cu(In, Ga)Se2 Solar Cell Performance,” Physica Status Solidi (a), Vol. 212, No. 2, pp. 282290 (2015). doi: 10.1002/pssa.201431388
  17. [17] Sharbati, S., Keshmiri, S. H., McGoffin, J. T. and Geisthardt, R., “Improvement of CIGS Thin-film Solar Cell Performance by Optimization of Zn(O,S) Buffer Layer Parameters,” Applied Physics A, Vol. 118, No. 4, pp. 12591265 (2015). doi: 10.1007/s00339- 014-8825-1
  18. [18] Lin, P. J., Lin, L. Y., Yu, J. L., Cheng, S. Y., Lu, P. M. and Zheng, Q., “Numerical Simulation of Cu_2ZnSnS_4 Based Solar Cells with In2S3 Buffer Layers by SCAPS1D,” Journal of Applied Science and Engineering, Vol. 17, No. 4, pp. 383390 (2014). doi: 10.6180/jase. 2014.17.4.05
  19. [19] Wanda, M. D., Ouédraogo, S., Tchoffo, F., Zougmoré, F. and Ndjaka, J. M. B., “Numerical Investigations and Analysis of Cu2ZnSnS4 Based Solar Cells by SCAPS1D,” International Journal of Photoenergy, Vol. 2016, No. 4, pp. 19 (2016). doi: 10.1155/2016/2152018
  20. [20] Sharbati, S. and Sites, J. R., “Impact of the Band Offset for n-Zn(O,S)/p-Cu(In,Ga)Se2 Solar Cells,” Photovoltaics, IEEE Journal of, Vol. 4, No. 2, pp. 697702 (2014). doi: 10.1109/JPHOTOV.2014.2298093
  21. [21] Sozzi, G., Troni, F. and Menozzi, R., “On the Combined Effects of Window/buffer and Buffer/absorber Conduction-band Offsets, Buffer Thickness and Doping on Thin-film Solar Cell Performance,” Solar Energy Materials and Solar Cells, Vol. 121, pp. 126136 (2014). doi: 10.1016/j.solmat.2013.10.037