Abstract
The effects of water vapor introduction during the growth of Cu(In~1–x~ Ga~x~ )Se~2~, specifically CuInSe~2~ (CISe), Cu(In,Ga)Se~2~ (CIGSe), and CuGaSe~2~ (CGSe) thin films were studied. We have developed thus far a novel technique to improve CIGSe (x ∼ 0.5) cell performance by means of water vapor introduction during CIGSe deposition. In this study, we have examined the effectiveness of water vapor introduction for other x ‐compositions (CISe and CGSe). Variations in the electrical properties observed in CIGSe (x ∼ 0.5), that is, increasing hole density and conductivity with water vapor introduction, were also observed in CISe and CGSe. Water vapor introduction affected solar cell performance as well; open circuit voltages, short circuit current densities, and efficiencies were improved. The improvements in cell performance are thought to be related to annihilation of donor defects arising from Se‐vacancies by incorporation of oxygen from the water vapor. In addition to this, the sodium content in the CIGSe layers was found to depend on the partial pressure of water vapor during deposition. This result suggests that the improvement mechanism is also related with the so‐called ‘Na‐effects'. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)