Fabrication of high-quality ZnS buffer and its application in Cd-free CIGS solar cells

Abstract

This paper provides the fabrication of Cd-free Cu(In,Ga)Se₂ (CIGS) solar cells on soda-lime glass substrates. A high quality ZnS buffer layer is grown by chemical bath deposition (CBD) process with ZnSO₄-NH₃-SC (NH₂)₂ aqueous solution system. The X-ray diffraction (XRD) result shows that the as-deposited ZnS film has cubic (111) and (220) diffraction peaks. Scanning electron microscope (SEM) images indicate that the ZnS film has a dense and compact surface with good crystalline quality. Transmission measurement shows that the optical transmittance is about 90% when the wavelength is beyond 500 nm. The bandgap (E_g) value of the as-deposited ZnS film is estimated to be 3.54 eV. Finally, a competitive efficiency of 11.06% is demonstrated for the Cd-free CIGS solar cells with ZnS buffer layer after light soaking.

Keywords

Solar Cell / Buffer Layer / Chemical Bath Deposition / Good Crystalline Quality / Competitive Efficiency

References

[1] Green M A, Emery K, Hishikawa Y, Warta W, Dunlop E D. Progress in Photovoltaics: Research and Applications. 2013, 21: 827

[2] Li B-y, Zhang Y, Liu W, Sun Y. Optoelectronics Letters. 2012, 8: 348

[3] Xin Z-y, Chen X-m, Qiao Z-x, Wang H, Xue Y-m, Pan Z, Tian Y. Optoelectronics Letters. 2013, 9: 112

[4] Orgassa K, Rau U, Nguyen Q, Schock H W, Werner J H. Progress in Photovoltaics: Research and Applications. 2002, 10: 451

[5] Nakada T, Kunioka A. Applied Physics Letters. 1999, 74: 444

[6] Nakada T. Thin Solid Films. 2000, 361–362: 346

[7] Jiang C S, Hasoon F S, Moutinho H R, Al-Thani H A, Romero M J, Al-Jassim M M. Applied Physics Letters. 2003, 82: 127

[8] Yan Y, Jones K M, Abushama J, Young M, Asher S, Al-Jassim M M, Noufi R. Applied Physics Letters. 2002, 81: 1008

[9] Nakada T, Mizutani M. Japanese Journal of Applied Physics. 2002, 41: L165

[10] Bhattacharya R N, Contreras M A, Teeter G. Japanese Journal of Applied Physics. 2004, 43: L1475

[11] Liu F F, Zhang L, He Q. Acta Phys. Sin.. 2012, 62: 077201

[12] Zhang L, He Q, Jiang W L, Li C J, Sun Y. Chinese Physics Letter. 2009, 26: 026801

[13] Zhang L, He Q, Jiang W L, Liu F F, Li C J, Sun Y. Solar Energy Materials and Solar Cells. 2009, 43: 93

[14] Zhang L, Liu F F, Li F Y, He Q, Li B Z, Li C J. Solar Energy Materials and Solar Cells. 2012, 99: 356

[15] Liu Q, Mao G B, Ao J P. Applied Surface Science. 2008, 254: 5711

[16] Oladeji I O, Chow L. Thin Solid Films. 1999, 339: 148

[17] Nakada T, Hongo M, Hayashi E. Thin Solid Films. 2003, 431–432: 242