Comparison of ZnS Film Growth on Glass and CIGS Substrates via Hydrazine-assisted Chemical Bath Deposition for Solar Cell Application

Abstract

We investigate the effect of hydrazine on the growth and physical characteristics of ZnS thin films deposited on both soda–lime glass (SLG) and copper indium gallium selenide (CIGS)/Mo/SLG substrates as a function of the relative molar ratio of hydrazine to ammonia reagent, rc, for various deposition times td. As rc is varied from 0 to 0.56, all the ZnS films on SLG (thickness of d ~ 38 nm) with hydrazine exhibit an amorphous structure, [S/Zn] composition of ~ 0.65, and direct energy bandgap of Eg = 3.54 – 3.75 eV. To compare the difference in device quality corresponding to the two types of substrates, we fabricate CIGS solar cells using ZnS buffers grown under conditions of rc= 0.28, 0.42 for td = 30 min, 15 min and without hydrazine with rc = 0.0 and td = 90 min. The sample obtained with the ZnS buffer under conditions of rc = 0.28, td = 30 min exhibits the best solar cell performance of η = 12.03 %. Our results prove that using hydrazine for ZnS buffer layer preparation via chemical bath deposition can significantly enhance the film quality for CIGS solar-cell fabrication.