Design of a Unique Hole-Transporting Molecule via Introducing a Chloro-Involved Chelating Moiety for High-Performance Inverted Perovskite Solar Cells

Abstract

Hole-transporting materials (HTMs) play an important role in transporting photogenerated holes, tuning the perovskite crystallization process, and passivating uncoordinated Pb2+ defects for high-performance inverted perovskite solar cells (PSCs). Herein, a unique cost-effective small molecule-type HTM based on a triarylamine core bearing a chloro-assisted chelating moiety (named TPA-CAA) is synthesized, which has excellent affinity to the perovskite precursor solution leading to smooth and uniform perovskite films. In comparison with the structurally similar molecule TPA-AA with the absence of the chloro-substituent, TPA-CAA can form a chelate structure with Pb2+ via the carbonyl and the adjacent chloro-atom, which efficiently tunes the perovskite crystallization, passivates the defects, and enhances the hole transporting at the perovskite/HTL interface. Eventually, the TPA-CAA-based inverted PSC achieves a champion power conversion efficiency (PCE) of 21.56% (19.64% and 18.84% for the poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and TPA-AA ones, respectively) with a high open-circuit voltage (VOC) of 1.113 V. Moreover, the stability of the TPA-CAA-based device is notably improved, and the PCE maintains over 80% of its initial value over 1000 h storage in ambient air (25 °C, relative humidity 30–40%) without encapsulation, in comparison to that of the PTAA device (only 50% of the initial value left over 1000 h).