The effect of O2 on H2Se selenization in a continuous flow reactor

Cu-In bilayers were reacted to form CuInSe₂ in a continuous flow tubular reactor using a dilute H₂Se mixture. The system was evacuated to 1×10^-6 torr prior to the introduction of the reacting gas to remove all gas phase contaminants. High efficiency solar cells could not be made on CuInSe₂ films formed using only H₂Se as the reacting gas. However, by mixing O₂ with the H₂Se, CuInSe₂ was formed and cells with efficiencies over 10% were fabricated. The O₂ reacts with the H₂Se in the gas phase forming Se_x species. At O₂/H₂Se ratios of 0.9 to 0.2, Cu₇Se₄ and In₂O₃ along with CuInSe₂ are formed. At low O₂/H₂Se ratios, 0.02 to 0.004, single phase CuInSe₂ films are formed which are suitable for devices