Wide-Bandgap III-V Solar Cells for Indoor Light Energy Harvesting

Wireless sensor networks will play a key role in reducing the energy consumption of smart buildings and data centres through intelligent environmental monitoring that can feedback to HVAC systems. Energy harvesting systems provide power autonomy to individual sensor nodes allowing simpler deployment as compared to wired- nodes and longer lifetimes than battery-powered ones. Indoor light energy is an abundant source in many applications where solar cells are used to convert the radiant energy to electricity. To date amorphous silicon and dye-sensitised solar cells have been the highest performing PV materials used in indoor light harvesters due to their narrower absorption edge than other materials. Here we show experimentally that III-V solar cells made from GaAs and GaInP significantly outperform those devices with power densities of greater than 2x measured under illumination by CFL and LED light sources. The superior performance is a function of their absorption characteristics and the very low reverse saturation currents inherent in high quality, direct bandgap, single-crystal semiconductor solar cells. Our experiments show a 30 cm2 GaInP solar cell provides 0.46 mW or 2.75 mW when located in a dimly lit corridor (200 lux) or bright office space (1000 lux) respectively.