Anion Effect of Zinc Source on Chemically Deposited ZnS(O,OH) Films
The study on the anion effect of different Zn sources—Zn(CH3COO)2, ZnCl2, ZnI2, Zn(NO3)2and 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)nin the chemical bath solution. In the region ofpKZn(NH3)2+>pKZn(L)nthe 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 theZn[NH3]2+complex and decreased in the region wherepKZn(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)2as Zn source, which provided the highest growth rate and ZnS concentration in the ZnS(O,OH) film on glass substrates.