Hydrogen bonding drives the self-assembling of carbazole-based hole-transport material for enhanced efficiency and stability of perovskite solar cells

Abstract

Designing a hole-transport material (HTM) that guarantees effective hole transport while self-assembling at the perovskite|HTM interface with the formation of an ordered interlayer, has recently emerged as a promising strategy for high-performance and stable perovskite solar cells (PSCs). Hydrogen bonding (HB) is a versatile multi-functional tool for the design of small molecular HTMs. However, to date, its employment is mostly limited to p-i-n inverted PSCs. This study demonstrates the advantages of a novel HTM design that can self-assemble into a long-range ordered interlayer on the perovskite surface via HB association. A hydro-functional HTM (O1) is compared to a reference HTM (O2) that cannot form HB due to the replacement of the amide group of O1 with a plain butyl alkyl chain in O2. As a result, O1-based n-i-p PSCs display enhanced hole extraction reaction, suppressed interfacial charge recombination, reduced hysteresis effect, and an increase in Voc (by 60 mV), FF (>11% increase), and overall power conversion efficiency, PCE (32% increase) compared to the case of HB-free O2-based devices. Remarkable stability is observed for unencapsulated O1 cells, with a T80 lifetime of 35.5 h under continuous maximum power point tracking in air. This work emphasizes the role of HB-directed self-assembling in simultaneously enhancing both the PCE and stability of popular n-i-p PSCs. This study paves the way for the development of new hydro-functional charge-transport material designs for efficient and stable PSCs.