Metalorganic Vapor-Phase Epitaxy Growth of GaAs Rear-Heterojunction Solar Cells at 94 µm/h

Abstract

In this study, a GaAs single-junction solar cell with an absorber layer grown at a very high rate of 94  µm/h via metalorganic vapor-phase epitaxy (MOVPE) is demonstrated, employing a low V/III ratio of 5. This approach enables the deposition of a 2.4 µm thick absorber layer in just 100 s, drastically lowering production time compared to conventional MOVPE rates below 10 µm/h. The solar cell achieves an excellent open-circuit voltage of 1061 mV and a fill factor of 83.2% using optimized growth conditions, matching the performance of state-of-the-art GaAs cells on bulk substrates grown at slow rates with much higher V/III ratios. At these high growth rates, increased defect densities of EL2 for electrons and HM1 for holes have been observed leading to promoted non-radiative recombination lowering the device performance. The GaAs absorber layer is engineered to minimize the impact of those defects, such that high solar cell efficiency is successfully maintained, despite the accelerated growth rate of 94 mm/h. This work not only showcases the feasibility of high-throughput, cost-effective production of high-efficiency III–V solar cells via MOVPE but also highlights potential environmental benefits from reduced material use and waste treatment.