Control of the thin film properties of Cu(In,Ga)Se₂ using water vapor introduction during growth

The effects of water vapor introduction during growth on Cu (In,Ga) Se2 (CIGSe) thin film properties, specifically the electrical and photoluminescence (PL) properties have been studied. Increases in the hole carrier density and conductivity with water vapor introduction were observed for all [Ga] [In+Ga] composition ratios. The PL spectra observed from CuGa Se2 (CGSe) showed an annihilation of deep donor-acceptor pair emissions related to Se vacancies with water vapor introduction. In addition, the Na content in the CIGSe layers as well as the O content was found to increase. These results suggest that the mechanism behind the variation observed in the electrical and PL properties and consequent cell improvement is largely attributable to a decrease in the Se-vacancies-induced donor defect density and an enhancement of Na effects.