A new effect is being developed which significantly improves the conversion efficiency of antireflection‐coated metal‐oxide‐semiconductor ‘AMOS’ solar cells. The effect, a marked increase in the open‐circuit voltage, is produced by the addition of an oxide layer to the semiconductor. Cells using gold onn‐type gallium arsenide have been made with efficiencies up to 15% in terrestrial sunlight. All processing steps are amenable to the use of low‐cost polycrystalline films of GaAs in place of the single crystals now used.