The role of thermalisation in hot carrier cooling dynamics

Abstract: The hot carrier solar cell (HCSC) concept has been proposed to overcome the Shockley Queisser limit of a single p-n junction solar cell by harvesting carriers before they have lost their surplus energy. A promising family of materials for these purposes is metal halide perovskites (MHP). MHPs have experimentally shown very long cooling times, the key requirement of a HCSC. By using Ensemble Monte Carlo (EMC) simulations we shed light on why cooling times are found to be extended for these materials. In this manuscript, we concentrate on the role of thermalisation in the cooling process. We specify the role of electron-phonon and electron-electron interactions in thermalisation and cooling, while furthermore showing how these processes depends on several relevant material parameters, such as the dielectric constant and the effective mass. Finally, we quantify how thermalisation can also act as a cooling mechanism via the cold background effect. Here, we stress the importance of a low degree of background doping in order to achieve the observed extended cooling times. This work provides insights into the ongoing discussion on cooling times in MHPs. In addition our results are an important addition to the debate on whether or not tin perovskites are suitable candidates for HCSCs.