Multi-functional thermal management for efficient and stable inverted perovskite solar cells

Abstract

Thermal-induced self-degradation and recombination losses greatly impact the performance of inverted perovskite solar cells (PSCs). Herein, a multi-functional thermal management strategy based on ionic liquids (1-butyl-3-methylimidazole dibutyl phosphate, BMDP) is proposed for the first time to overcome these challenges for excellent thermal stability and efficiency in inverted PSCs. The BMDP can diffuse into grain boundaries (GBs) and stay at the surface perovskite film, resulting in efficient thermal management, trap passivation, ion migration elimination, hydrophobic improvement, as well as interface electric field enhancement. With the help of BMDP, the thermal conductivity of the perovskite film and the device at high temperatures were enhanced by 32.56% and 61.90%, respectively. In addition, the heat dissipation speed device was also accelerated. The power conversion efficiency (PCE) of the unencapsulated devices based on the intrinsically unstable MAPbI₃/PCBM heterojunction can maintain about 90% of the initial value, whether at 85 °C for 1080 h, or in air (RH = 30 ± 5%, 25 °C) for 1440 h, which is one of the most reported stable results based on the thermally unstable MAPbI₃/PCBM heterojunction to date. Furthermore, the high PCE can be improved greatly with this multi-functional thermal management, and the highest PCE of 21.98% and 23.25% have been achieved in the inverted devices based on MA/I and Rb/Cs/FA/MA/I/Br perovskite systems.