Understanding the Trap Characteristics of Perovskite Solar Cells via Drive-Level Capacitance Profiling

Perovskite solar cells (PSCs) are gaining significant interest as the future of photovoltaics owing to their superior performance and cost-effectiveness. Nevertheless, traps in PSCs have emerged as issues that adversely affect the efficiency and stability of the devices. In this study, the methylammonium chloride (MACl) additive and phenyltrimethylammonium iodide (PTMAI) posttreatment were applied to passivate bulk and surface defects. Furthermore, variations of the traps' quantitative spatial arrangement have been monitored by using the drive-level capacitance profiling (DLCP) analysis. A similar magnitude of trap reduction was observed for the bulk perovskite layer and two interfaces (electron transport layer (ETL)/perovskite and hole transport layer (HTL)/perovskite) with an optimal concentration of the MACl additive. However, the effect of perovskite posttreatment in reducing the trap density was much more noticeable at the HTL/perovskite interface compared to the bulk and ETL/perovskite regions. This observation was reinforced by the outcomes of the 500 h thermal stability tests at 60 °C from seven independent batches, which demonstrated a substantial suppression of trap accumulation, particularly at the HTL/perovskite interface, by an order of magnitude.