Postannealing in Metal–Organic Chemical Vapor Deposition Reactor: A Scalable Method for Improving InGaAsP Solar-Cell Efficiency

InGaAsP solar cells with a bandgap of approximately 1.05 eV, which are lattice matched to InP substrates, generally exhibit relatively lower crystal quality and energy conversion efficiency compared with other III–V compound semiconductor solar cells, such as the GaAs solar cell. This is mainly owing to the challenges in achieving a uniform chemical composition and reducing nonradiative recombination defects during the growth process. In this study, we effectively addressed this challenge by directly performing postannealing within the metal–organic chemical vapor deposition system. Following annealing, the open-circuit voltage (VOC) and short-circuit current density (JSC) of the solar cells were improved by 38 mV and 3.84 mA/cm2, respectively. The analysis of voltage losses, along with time-resolved photoluminescence results, revealed that the improvements inVOCandJSCwere attributed to the reduction of nonradiative recombination defects and enhancement of carrier lifetime, respectively. X-ray diffraction analysis showed a reduction in the full width at half maximum of the peak in annealed InGaAsP samples, indicating that annealing significantly enhanced the compositional uniformity of the material, which was likely driven by the redistribution of group-III atoms (In and Ga in InGaAsP) during the thermal annealing process. In addition, low-temperature photoluminescence results confirmed a reduction in nonradiative recombination defects, further corroborating the findings from the voltage-loss analysis. Postannealing treatments have significantly enhanced the crystal quality of InGaAsP, leading to a notable 32% improvement in the efficiency of InGaAsP solar cells in the best cases. Thus, this study highlighted annealing as an effective and scalable approach to optimizing the growth process for InGaAsP-based solar cells.