Role of built-in potential over ETL/perovskite interface on the performance of HTL-free perovskite solar cells

Lead-free, Sn-based perovskite solar cells (PvSCs) have piqued the interest of researchers and their commercialization. Hole transport layer (HTL)-free PvSCs are low-cost and easy to fabricate. The built-in potential of a photovoltaic (PV) device plays an essential role in the separation of light-generated charge carriers. In this simulation work, we have investigated the built-in potential at the interface of electron transport layer (ETL) and Formamidinium tin iodide (FASnI(3)) with the help of Mott-Schottky plot for various types of ETLs. We have measured how the built-in potential was affected by thickness, doping density, and defect density of FASnI(3) perovskite absorber layer and found that the built-in potential of ETL/FASnI(3) interface had a significant impact on the device performance parameters. The built-in potential greatly affects the Shockley-Read-Hall (SRH) recombination mechanism. In this simulation, the material parameters of each layer have been optimized and obtained an optimized PCE of more than 16% for all devices. It is anticipated that the results of this study have great potential to understand the role of built-in potential in n-p junction PV devices and consequently device optimization of not only for HTL-free FASnI(3)-based PvSCs but also for other single n-p junction PvSCs. However, the fabrication of HTL-free FASnI3-based PvSCs is still a challenging task due to the oxidation of Sn2+ to Sn4+.