Opportunities for Increased Efficiency in Monochromatic Photovoltaic Light Conversion

We study efficiency loss mechanisms and the potential for improvement of a record-setting monochromatic photovoltaic device, which has demonstrated efficiency of 70% at 830 nm. We combine experimental and modeling-based estimates of losses due to reflection, transmission, thermalization, and series resistance into an extended detailed-balance model that further includes losses due to nonradiative recombination, quantified by an external radiative efficiency (ERE). From the device's efficiency, we estimate ERE ≥ 10%. The device efficiency could be improved by increased material quality, operation at a longer wavelength closer to the GaAs band gap, and increased light intensity. Each order of magnitude increase in incident light intensity or material ERE increases the efficiency by 4% absolute. Redesigning the device to operate at 850 nm reduces thermalization losses by 2% absolute. Overall device efficiency over 80% could be attained by combining these opportunities.