Light manipulation for mutual enhancement in cooling and energy harvesting of photovoltaics

Abstract

The introduction of radiative cooling lightens managing a heat load of photovoltaic (PV) without energy consumption. Owing to the passive and compact cooling principle, many scientists and engineers have studied a radiative cooler itself and effective integrating systems with PV. However, most research focused on the design of radiative cooler only considering thermal emission, not collecting solar energy more. Also, these reports have stayed within computational studies based on silicon solar cell, which uses only a part of solar spectrum. Herein, we present a high-efficient/radiatively cooled multi-junction solar cell (MJSC; InGaP/GaAs/Ge), which utilizes most solar spectrum, by introducing bi-functional solar window (BFSW), which separately works in solar and long wave infrared regions. The micro-patterns in BFSW brings to not only remarkable self-cooling feature resulted from amelioration of the emissivity loss, but also improved solar collecting capability owing to diffraction. By mounting the optimum BFSW on the MJSC, we confirm the improved cell efficiency from 25.4 to 26.7 % using solar simulator. Moreover, outdoor field tests successfully demonstrate the enhanced cooling performance and power conversion efficiency compared to conventional glass mounted MJSC under direct sunlight of ~ 900 W/m2: Temperature drop of ~ 5°C and minimizing the variation of open-circuit voltage as ~ 6%.