Minority carrier lifetime limitations in Si wafer solar cells with gallium phosphide window layers

III-V materials are very attractive top absorbers for highly efficient Si based multi-junction solar cells. In case of direct growth on Si wafers, a high quality hetero interface for the passivation of the silicon bottom cell should be achieved and the degradation of the Si minority carrier bulk lifetime has to be avoided. In this paper we show that diffusion barriers can reduce the contamination of the Si absorber and lead to minority carrier lifetimes of 1120 μs after thermal treatment at 1050 °C in the metal-organic vapor phase epitaxy reactor. With an adapted growth and solar cell process we could fabricate Si solar cells with an open circuit voltage of 634 mV.