On the fundamental efficiency limits of photovoltaic converters for optical power transfer applications

Dedicated photovoltaic converters for the conversion of monochromatic laser radiation (laser power converters (LPCs)) have been developed for high efficiency conversion of laser radiation at 1550 nm into electrical power. The LPC design is based on the InGaAsP/InP material system and achieves a maximum conversion efficiency of 45 % (±1%) under 1.55 μm illumination at 1 kW/m² at room temperature. We have experimentally mapped out the conversion efficiency of the LPC as a function of temperature (100-300 K) and incident wavelength (tracking the absorber band-edge) in order to investigate the efficiency limiting mechanisms. The LPC achieves a conversion efficiency of 80% (± 5 %) at 100 Kelvin, highlighting the importance of various temperature dependent loss mechanisms (radiative-, SRH-, Auger-recombination etc.) which limit the conversion efficiency for photovoltaic converters under normal operation conditions. Here we discuss the experimental results linking them to the various loss mechanisms using a detailed theoretical model and underline important design considerations which should prove useful for developing future high efficiency photovoltaic cells for both solar and laser illumination.