Dimethylamine Exchanging of a New Hole Transport Material for Highly efficient CsPbI2Br solar cells

All inorganic α-CsPbI2Br films with a large open circuit voltage (V OC) and excellent thermal stability are promising for highly stable and efficient perovskite solar cells (PSCs). However, its device performance is limited by a low short circuit current density (J SC) and low V OC, which is strongly related to the energy misalignment and defects recombination at the perovskite/transport layer interfaces. In this work, we develop two Ni based polymers: bis (dithiobenzil) nickel (II) (BDTB) and bis(4-dimethylaminodithiobenzil) nickel (II) (BDMA), and use them as the hole transport layer for α-CsPbI2Br PSCs. As compared to BDTB based reference device (PCE ~3.2%), BDMA based device demonstrate a simultaneous increase on V OC, J SC and fill factor (FF), resulting in a remarkable power conversion efficiency (PCE) of 13.32 %. We attribute the improved device performance to a better interfacial alignment, the reduced defect recombination and improved charge extraction. Moreover, the BDMA based devices also exhibit an improved shelf-life stability than BDTB control device, which sustain over 80 % of PCE after 50 days in ambient air.