Extended detailed balance modeling toward solar cells with cement-based radiative coolers

Reducing the temperature of a solar cell increases its efficiency and lifetime. This can be achieved by radiative cooling, a passive and simple method relying on materials that dump heat into outer space by thermal emission within the atmosphere transparency window between 8 and 13 mu m$$ 13\kern0.1em \upmu \mathrm{m} $$. As most radiative coolers are expensive or possibly UV unstable, we have recently proposed cement-based solutions as a robust and cost-effective alternative. However, the assessment model used describes the cell in the radiative limit and with perfect thermal coupling to the cooler, in line with the literature. In this work, we lift these two approximations, by incorporating Auger and Shockley-Read-Hall nonradiative recombination and a finite heat transfer coefficient at the cell/cooler interface, to obtain a thermal description of the cell/cooler stack closer to reality, while preserving the universality and transparency of the detailed-balance approach. We use this model to demonstrate that the cell performance gains provided by a radiative cooler are underestimated in the radiative limit and are hence more prominent in devices with stronger nonradiative recombination. Furthermore, we quantify the relation between cell temperature and heat transfer coefficient at the cell/cooler interface and show how this can be used to define design requirements. The extended model developed, and the resulting observations provide important guidelines toward the practical realization of novel radiative coolers for solar cells, including cement-based ones. This work extends the detailed-balance model commonly used to assess radiative coolers for solar cells by incorporating the impact of Auger and Shockley-Read-Hall nonradiative recombination and of a thermal contact resistance at the cell/cooler interface. New insights and guidelines for the practical realization of radiative coolers are provided with emphasis on recently proposed cement-based ones, deemed attractive because of potential low-cost, scalability, and applicability in the context of building-integrated photovoltaics.image