Progress in amorphous semiconductorsolar cell technology at RCA Laboratories and other research organizations is reviewed. The performance of cells is discussed for homojunction p‐i‐n structures and structures utilizing hydrogenated amorphous alloys of Si–C, Si–F, Si–Ge, and B–Si. Recently, several organizations have reported conversion efficiencies in the range of 6.0 %–7.5 % for homojunction p‐i‐n cells and structures using alloys of Si–C–H and Si–F–H. The effects of various impurities on solar‐cell performance are discussed. We also present data on the diffusion of various contact materials and dopants in amorphous Si at elevated temperatures.