Bifunctional passivation by lewis-base molecules for efficient printable mesoscopic perovskite solar cells

Abstract

Printable mesoscopic perovskite solar cells (PM-PSCs) possess notable merits in terms of cost-effectiveness, easy manufacturing, and large scale applications. Nevertheless, the absence of a hole transport layer contributes to the exacerbation of carrier recombination, and the defects between the perovskite and electron transport layer (ETL) interfaces significantly decrease the efficiency of the devices. In this study, a bifunctional surface passivation approach is proposed by applying a thioacetamide (TAA) surfactant on the mesoporous TiO2 interface. The results demonstrate that TAA molecules could interact with TiO2, thereby diminishing the oxygen vacancy defects. Additionally, the amino group and sulfur atoms in TAA molecules act as Lewis base to effectively passivate the uncoordinated Pb2+ in perovskite and improve the morphology of perovskite, and decrease the trap-state density of perovskite. The TAA passivation mechanism improves the alignment of energy levels between TiO2 and perovskite, facilitating electron transport and reducing carrier recombination. Consequently, the TAA-passivated device achieved a champion power conversion efficiency (PCE) of 17.86% with a high fill factor (FF) of 79.16% and an open-circuit voltage (VOC) of 0.971 V. This investigation presents a feasible strategy for interfacial passivation of the ETL to further improve the efficiency of PM-PSCs.