Intrinsic losses in photovoltaic laser power converters

Abstract

Using photovoltaic cells as photovoltaic laser power converters (PLPCs) is a potential technology for long-range wireless power transfer. Intrinsic processes that limit the performance of PLPCs have not been fully investigated. Based on a thermodynamic model, we categorize and calculate the intrinsic losses in PLPCs. We use the experimental data of silicon and gallium arsenide to take into account the unavoidable Auger process. We find that the entropic loss generated during the absorption and emission of radiation is the major loss mechanism. Importantly, we show that in the presence of nonideal absorptivity and volumetric entropy production via Auger recombination, using lasers with photon energy equal to the bandgap of the PLPC can be impractical, e.g., comparable efficiencies can be achieved in much thinner silicon PLPCs illuminated by lasers with higher photon energies. We also investigate the methods of diminishing the intrinsic losses with respect to the Auger process: by intensifying the laser irradiance, the proportion of entropic loss in input power can be arbitrarily reduced; by using spectral and angular filters, the intrinsic losses can be diminished via absorption enhancement or emission restriction. Additionally, we discuss the practical efficiency limit of PLPCs accounting for the entropy production due to finite carrier mobilities. The results in this work estimate the potentials for efficiency improvements, which are fundamental to the design of PLPCs.