(A) way of evaluate the minority-carrier lifetime by using photoluminescence (PL) measurement is proposed which includes self-absorption. The room-temperature PL intensity is analyzed theoretically for bulk crystals and a device with n(+)-p junction configuration, based on a one-dimensional model. Photoluminescence analysis of In0.5Ga0.5P solar cells gown on GaAs and Si substrates by MOCVD (metal organic vapor deposition) have been carried out and compared with the properties of the In0.5Ga0.5P solar cells. By improving minority-carrier lifetime, high-efficiency In(0.5)Gao(0.5)P cells on GaAs substrates with an efficiency of 18.5% have been made.