Enhanced Performance and Stability of Perovskite Solar Cells Using NH₄I Interfacial Modifier

Despite organic-inorganic hybrid perovskite solar cells have rapid advances in power conversion efficiency in recent years, the serious instability of the device under practical working conditions is the current main challenge for commercialization. In this study, we have successfully inserted NH₄I as an interfacial modifier between the TiO₂ electron transport layer and perovskite layer. The result shows that it can significantly improve the quality of the perovskite films and electron extraction efficiency between the perovskite and electron transport layer. The devices with NH₄I are obtained an improved power conversion efficiency of 18.31% under AM 1.5G illumination (100 mW cm^-2). More importantly, the humidity and UV light stability of the devices are greatly improved after adding NH₄I layer. The uncoated devices only decrease by less than 15% of its original efficiency during 700-h stability tests in a humidity chamber (with a relative humidity of 80%) and the efficiency almost maintains 70% of its initial value over 20 h under UV light stress tests. This work provides a potential way by interfacial modification to significantly improve photovoltaic performance and stability of perovskite solar cells.