Introduction of 4-hydroxybenzaldehyde as interface modifier with multidimensional defects passivation effect for high-performance perovskite solar cells

[Display omitted] •4-hydroxybenzaldehyde with multifunctional groups was employed as interfacial modification material.•The passivation effect of –CHO and –OH groups on the various types of defects was studied.•Modified perovskite films owned fewer defects density and reduced non-radiative recombination.•The devices with 4-hydroxybenzaldehyde achieved high PCE increased to 20.89% and excellent stability. The various types of surfaced point defects and grain boundaries (GBs) of perovskite films have become an obstacle to the development of the overall power conversion efficiency (PCE) and long-term stability of perovskite solar cells (PSCs). Recently, the interfacial modification engineering has been demonstrated as an efficient strategy to reduce defects density and suppress non-radiative recombination. Herein, we report a novel interfacial modification material, 4-hydroxybenzaldehyde (HBA) with multifunctional groups (–CHO and –OH) to modify the interface between perovskite film and hole transport layer (HTL). It is found that the HBA interfacial modifier cannot only passivate one-dimensional point defects, including uncoordinated lead ion (Pb2+) and FA+/MA+ vacancies by coordination interaction or hydrogen bond, but also passivate two-dimensional extended defects via promoting secondary growth of grains to reduce the number of GBs. Consequently, the PCE is significantly improved from 18.84% for the control device to 20.89% for HBA-modified device. Meanwhile, the device with HBA interfacial modifier exhibits negligible hysteresis and excellent environmental stability against humidity and thermal. This study provides important insight to reasonably design passivation molecular structure for obtaining highly efficient and stable PSCs.