Photovoltaic Enabled Indoor Light Harvesting

By the mid-2020s it is predicted that billions of sensors and other IoT devices will be deployed worldwide monitoring every aspect of our environment. These devices require electrical power with batteries being the preferred choice when hard-wiring is impractical or too expensive. Other alternatives to batteries are being advanced and particularly for the indoor environment harvesting the ‘free’ artificial and / or externally transmitted light seems a tangible possibility.<br/>It is becoming more appreciated that the design of an optimised and integrated PV system for indoor light harvesting is very different to conventional solar cells. Artificial lighting sources have bespoke spectral characteristics (consider warm and cool white LEDs) radically different to AM1.5G, and indoor lighting is low intensity (&lt; 500 lux). The question thus arises – what type of PV is best suited to this emerging application? Answering this question involves thermodynamic considerations such as the optimal bandgap in the radiative limit, generation and transport losses under low photo-generated carrier concentrations, additional voltage losses due to shunt, etc. We must also consider architectural approaches such as doubly transparent contacts and cell interconnection to deliver appropriate voltages and currents.<br/>In my talk I will expand upon these basic considerations for the specific case of organic and organohalide perovskite PV and compare and contrast with other systems including silicon and compound semiconductors. Specifically, I will discuss the optimum bandgap for typical indoor lighting sources and advance a new predictive model to assess the performance of various materials. This analysis allows for the specification of design rules for indoor light harvesting.