Synergistic effect of amide and fluorine of polymers assist stable inverted perovskite solar cells with fill factor > 83%

Abstract

Exploring hole transporting materials (HTMs) with defect passivation function is an effective way to suppress the defect-induced non-radiative recombination (NRR) process in perovskite solar cells (PSCs). To date, most of these passivation materials are mainly devoted to passivate the uncoordinated Pb2+ of perovskite layer. However, ion migration processes of MA+ and I- in PSCs also cause a series of negative effects, which severely deteriorate the efficiency and device stability. Thus far, very few HTMs that can simultaneously passivate both the MA+/Pb2+ cations and I- anion defects in ABX3 structured perovskite. Herein, three dopant-free HTMs (BNs, BNs-F, and BNo-F) featuring multisite defect passivation function were developed for inverted PSCs. The carbonyl groups C = O and N–H in the amide linkers of BNs-F contributed to passivate the uncoordinated Pb2+ and the halide related defects, respectively. Simultaneously, the F atoms in bridges could interact with MA+ in perovskite via N-H‧‧‧F bond. Interestingly, an intermolecular hydrogen bond (O = C-N-H‧‧‧F) between amide linkers and F atoms was found in our work, which enabled BNs-F to achieve a high hole mobility of 2.42 × 10-4 cm2 V−1 s−1. Consequently, benefiting from the alleviated NRR behavior and enhanced charge transport ability, the optimized devices based on BNs-F realized a remarkable fill factor of 0.834, accompanying a champion efficiency up to 20.56% with superior long-term stability, exceeding those with BNs (19.03%), BNo-F (19.07%) and PTAA (19.56%). Our findings provide a guidance for design molecules with comprehensive passivation effect on MA+/Pb2+/I- defects to achieve efficient and stable PSCs.