Improvement of Short-Circuit Current Density in GaInP Solar Cells Grown by Dynamic Hydride Vapor Phase Epitaxy

We demonstrate GaInP solar cells grown by dynamic hydride vapor phase epitaxy with improved efficiency through elimination of nonradiative recombination centers. We redesigned our reactor to eliminate unintentional impurities, which led to a reduction of nearly 30x in dark current. This improvement led to a significantly improved open-circuit voltage of 1.41 V and a band gap-voltage offset of 0.47 V in a device with a rear reflector, achieved without front surface passivation. We demonstrate that the limiting factor toward achieving higher efficiency is control over the emitter thickness. Recombination is high in the unpassivated emitter, but losses can be minimized by designing it to be thin. We show that Se diffusion from the GaAs contact layer into the base is responsible for unintentional thickening of the emitter. Use of reduced contact doping reduces the penetration of Se into the p-GaInP base layer. With improved control of Se diffusion, we achieve 13.0 mA/cm(2) and 15.2% certified efficiency in a single-junction GaInP cell structure that is optically equivalent to the top cell in a GaInP/GaAs tandem.