Benzalkonium chloride assisted quenching-free fabrication of nonalloyed FAPbI3 perovskite films and solar cells

Formamidinium lead triiodide (FAPbI 3 ) perovskite materials exhibit tremendous potential for next-generation solar cell applications. However, the fabrication of FAPbI 3 thin films usually requires a quenching treatment with a narrow processing window to achieve the desired morphology. Meanwhile, the use of methylammonium (MA)-containing additives assists the crystallization of FAPbI 3 but raises concerns on the device stability due to the residual MA cation. Here, we present a highly reproducible approach for quenching-free deposition of FAPbI 3 films without using any MA-containing additives. The bifunctional surfactant of benzalkonium chloride is found simultaneously contributing to a more compact multicrystalline films with reduced pinhole density, as well as a dramatically improved moisture stability of the quenching-free FAPbI 3 film. The corresponding FAPbI 3 perovskite solar cell exhibits a decent tolerance to minor pinholes and achieved a power conversion efficiency up to 23.5% under 1 sun illumination, and also presents improved storage and operational stability.