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

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 degrees 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). The chloro-assisted chelating hole transporting material (HTM) based on a triarylamine core for inverted perovskite solar cells and with the unique chelating interaction is demonstrated. The best interface contact and lowest trap density are obtained resulting in the best device performance.image

Automated summary

Hole-transporting materials (HTMs) are crucial for the performance of inverted perovskite solar cells (PSCs). This study presents a unique cost-effective small molecule-type HTM with a chloro-assisted chelating moiety (TPA-CAA). TPA-CAA shows excellent affinity to the perovskite precursor solution, resulting in smooth and uniform perovskite films. The chelate structure of TPA-CAA efficiently tunes the perovskite crystallization, passivates defects, and enhances hole transporting at the perovskite/HTL interface. The TPA-CAA-based inverted PSC achieves a champion power conversion efficiency (PCE) of 21.56% with improved stability.