Anion Effect of Zinc Source on Chemically Deposited ZnS(O,OH) Films

Abstract

The study on the anion effect of different Zn sources—Zn(CH3COO)2, ZnCl2, ZnI2, Zn(NO3)2 and ZnSO4—on the chemical deposition of ZnS(O,OH) films revealed that the growth rate and composition of the ZnS(O,OH) layer depend on the instability constant (pK) value of the corresponding Zn-complex Zn(L)n in the chemical bath solution. In the region of pKZn(NH3)2+>pKZn(L)n the ZnS(O,OH) film's growth rate and ZnS concentration in films increased with the increasing pK value of the used Zn salt complex up to the pK value of the Zn[NH3]2+ complex and decreased in the region where pKZn(NH3)2+<pKZn(L)n. The band gap values (around 3.6 eV in most cases) of deposited ZnS(O,OH) films did not depend on the Zn precursor's instability constant, the ZnS(O,OH) film from zinc nitrate containing bath has higher band gap energy (Eg = 3.8 eV). The maximum efficiency of CISSe and CZTSSe monograin layer solar cells was gained with ZnS(O,OH) buffer layer deposited from CBD solution containing Zn(CH3COO)2 as Zn source, which provided the highest growth rate and ZnS concentration in the ZnS(O,OH) film on glass substrates.