Improved eco-friendly CsSn0.5Ge0.5I3 perovskite photovoltaic efficiency beyond 20% with SMe-TATPyr hole-transporting layer

Abstract

Perovskites composed of inorganic cesium (Cs) halide provide a route to thermally resistant solar cells. Nevertheless, the use of hole-transporting layers (HTLs) with hydrophobic additives is constrained by moisture-induced phase deterioration. Due to significant electrical loss, dopant-free HTLs are unable to produce practical solar cells. In this article, we designed a two-dimensional 1,3,6,8-tetrakis[5-(N,N-di(p-(methylthio)phenyl)amino-p-phenyl)-thiophen-2-yl]pyrene (termed SMe-TATPyr) molecule as a new HTL to regulate electrical loss in lead-free perovskite solar cells (PSCs). We optimized the power conversion efficiency (PCE) of PSCs based on mixed tin (Sn)/germanium (Ge) halide perovskite (CsSn_0.5Ge_0.5I₃) by exploring different factors, such as the deep and shallow levels of defects, density of states at the valence band (N_V), thickness of the perovskite film, p-type doping concentration (N_A) of HTL, the series and shunt resistances, and so on. We carried out comparative research by employing the 1D-SCAPS (a solar cell capacitance simulator) analysis tool. Through optimization of the PSC, we obtained the highest parameters in the simulated solar cell structure of fluorine tin oxide (FTO)/titanium dioxide (TiO₂)/CsSn_0.5Ge_0.5I₃/SMe-TATPyr/gold (Au), and the PCE reached up to 20% with a fill factor (FF) of 81.89%.