Rational design of formamidine tin-based perovskite solar cell with 30% potential efficiency via 1-D device simulation.

As a promising photovoltaic technology, halide perovskite solar cells (PSCs) have recently attracted wide attention. This work presents a systematic simulation of low bandgap formamidinium tin iodide (FASnI)-based p-n heterojunction PSCs to investigate the effects of multiple optoelectronic variations on the photovoltaic performance. The structures of the simulated devices are n-i-p, electron transport layer-free (ETL-free), hole transport layer-free (HTL-free), and inverted HTL-free. The simulation is conducted with the Solar Cell Capacitance Simulator (SCAPS-1D). The power conversion efficiencies (PCEs) dramatically decrease when the acceptor doping density () of the absorber layer exceeds 10 cm. For all devices, the photovoltaic parameters dramatically decrease when the absorber defect density () is over 10 cm, and the best absorber layer thickness is 1000 nm. It should be pointed out that the and the interface defect layer (IDL) are the primary culprits that seriously affect the device performance. When the interfacial defect density () exceeds 10 cm, PCEs begin to decline significantly. Therefore, paying attention to these defect layers is necessary to improve the PCE. Furthermore, the proper conduction band offset (CBO) between the electron transport layer (ETL) and absorber layer positively affects PSCs' performance. These simulation results help fabricate highly efficient and environment-friendly narrow bandgap PSCs.