Heterogeneous seed-assisted FAPbI3 crystallization for efficient inverted perovskite solar cells

Abstract

The power conversion efficiencies (PCEs) of inverted perovskite solar cells (PSCs) have been demonstrated to exceed 26%. However, the uncontrolled crystallization process negatively affects the film quality, consequently limiting the overall performance of PSCs. To address these issues, we propose a novel heterogeneous seed-assisted strategy for FAPbI₃ crystallization to regulate the crystallization process and enhance the α-phase perovskite formation. In this strategy, the strong interactions between 2,4-diaminopyrimidine (DAP) and perovskite species inhibit the solvent-dominated intermediate phase formation and promote the formation of DAP-FA⁺[PbI₃]⁻ (δ) heterogeneous seeds. These seeds rapidly transform into the desired α-phase during the initial formation stage, assisting the subsequent crystallization process. Consequently, a highly crystalline α-FAPbI₃ film is obtained with reduced trap density and increased carrier lifetime, leading to an impressive PCE of up to 25.29% along with upgraded stability for inverted devices. Our findings provide valuable insights into innovative utilization of heterogeneous seeds for depositing high-quality α-FAPbI₃ films.