Buried bottom interface defect passivation of alternating cation interlayer phase quasi-two-dimensional perovskite solar cells

Abstract

Alternating cations in the interlayer space (ACI) phase quasi-two-dimensional (quasi-2D) perovskites have garnered significant attention due to their exceptional stability. However, there remains a gap in the power conversion efficiency (PCE) of the corresponding perovskite solar cells (PSCs) when compared to three-dimensional bulk perovskite materials. Herein, an interface passivation strategy involving the spin coating of 1,4-piperazine diethanesulfonic acid salts (PIPES salts) between the ACI phase perovskite (GA)(MA)_nPb_nI_3n+1 (where n = 5, guanidinium = GA, methylammonium = MA) and the self-assembled monolayer (SAM) was presented to passivate the buried bottom interface defects of PSCs. This strategy effectively reduced the surface potential of the SAM, minimized the accumulation of pinholes at the buried bottom interface, and improved the contact between the perovskite layer and the SAM. PIPES salts can interact with the perovskite and passivate the crystal defects, thereby reducing non-radiative recombination of carriers. The PSCs passivated by PIPES dipotassium salt achieved a PCE of 15.02%, and their stability was remarkably enhanced. This work underscores the importance of optimizing the buried bottom interface of ACI phase quasi-2D PSCs and offers new insights for the future research.