Voltage and efficiency characteristics of shifted-junction GaAs/GaInP thin-film solar cells and light emitters

Abstract

Junction shifting (i.e., pushing the p-n junction within a wider-bandgap confinement layer) is an effective strategy to suppress nonradiative recombination in GaAs/GaInP light-emitting diodes (LEDs). Advancing from our earlier wafer-based structures, we report fully processed thin-film GaAs/GaInP LEDs fabricated at the 2-in. wafer scale, incorporating both junction shifting and rear-side reflector texturing. Devices were characterized in photovoltaic (PV) and LED modes across different bias currents using reciprocity-based analysis. In PV measurements, rear-textured devices with a 300 nm GaAs active region exhibit an open-circuit voltage (Voc) of 1074.4 mV and an external radiative efficiency (ηext) of 8.8%, estimated from reciprocity relations at Voc. This represents a clear improvement over 4.95% in nontextured structures. Direct LED measurements of ηext confirm these trends: texturing doubles the peak wall-plug efficiency, reaching 24%, among the highest reported for GaAs thin-film LEDs without external optics. Analysis of dark current–voltage characteristics and ηext indicates internal radiative efficiencies consistent with state-of-the-art GaAs devices. These results confirm the high performance of the tested thin-film structures and demonstrate how PV-mode metrics, particularly Voc and ηext(Voc), can diagnose radiative losses and guide photon management strategies in thin-film emitters.