Cu₂O related defect impact on organic FASnI₃/MAPbI₃ solar cell performance

Usually, there are some discrepancies between simulations and measurements in Perovskite solar cells (PSCs). This is partially due to ignoring defects in transporting layers. In this work, realistic simulations were undertaken to study the effects of bulk defects in cuprous oxide (Cu₂O), the Hole Transporting Layer (HTL). Firstly, two different cell absorbers namely, the Br doped formamidinium tin iodide (Br-FASnI₃) and the methylammonium lead iodide (MAPbI₃), were considered. The thicknesses of the absorber, the electron transporting layer (ETL) (SnO₂), and the HTL (Cu₂O), were optimized, leading to 24.34% and 20.30% power conversion efficiencies (PCE) for MAPbI₃ and Br-FASnI₃, respectively. Furthermore, ETL doped antimony (Sb–SnO₂) showed better performance in MAPbI₃-based PSCs while multiple functional group organic molecule of 3-(formamidinothio)-1-propanesulfonic acid (FTPS) as additive to SnO₂ (FTPS–doped SnO₂) was better for Br-FASnI₃-based solar cells. Secondly, the impact of defects in Cu₂O was considered. In Br-FASnI₃ devices, the acceptors largely influence the PCE. So, by enhancing the open circuit voltage V_OC, especially the shallower level (0.16 eV), the PCE reached 27.97%. Their effect is less pronounced when they are deeper (1.3 eV). As for the donors, they tend to reduce V_OC. On the other hand, because in the MAPbI₃-based solar cell the ETL is already thin, the photogenerated electrons will be almost directly extracted, which reduces the collected current density J_SC and therefore the PCE. As for the HTL donor traps, their effect is similar to that in the Br-FASnI₃ solar cell, where they drastically reduce the PSC performance via the recombination process.