Solar cells consisting of have been fabricated by the liquid phase epitaxial growth of on substrates. The spectral response of the cells has been used to calculate the absorption coefficient of the alloy layer; the coefficient varies as , and indirect bandgaps of 2.071 and 2.094 eV for compositions of and , respectively, are indicated. The solar cell characteristics were measured in sunlight at Air Masses of 0.9 and 1.3 and in simulated sunlight at Air Mass 0; the open‐circuit voltages ranged from 0.97 to 1.0V, the short‐circuit currents from 20 to 22.5 mA/cm2, and the efficiencies (corrected for contact area) from 11.7 to 12.8% at Air Mass 0 and a temperature of 80°F. The short‐ circuit current and open‐circuit voltage increase and decrease, respectively, linearly with temperature. The efficiency has a maximum at around −75°C, and decreases at a rate of 0.022% per °C up to 200°C and at over twice that rate above 200°C. Efficiencies of almost 6% at 300°C and over 3% at 350° C were measured using a quartz‐halogen light source that simulates Air Mass 1.