Defects Passivation With Dithienobenzodithiophene-based pi-conjugated Polymer for Enhanced Performance of Perovskite Solar Cells

A dithienobenzodithiophene-based pi-conjugated polymer consisting of fluorinated benzotriazole and benzothiadiazole is successfully applied through anti-solvent method to passivate the defects of perovskite crystals. The fluorinated polymer interacts with under coordinated Pb2+ ions in the perovskite crystals to form Pb-F bond which effectively passivates the defects. The trap density is reduced and the charge carrier transfer between the perovskite film and Spiro-OMeTAD is also improved after passivation with the polymer. As a result, a power conversion efficiency (PCE) of 18.03% is achieved in the champion cell. After storing in an ambient environment with 60% relative humidity for 1000 h, the device still retains 90% of the original PCE. These results demonstrate that dithienobenzodithiophene-based pi-conjugated polymers are promising materials for passivation of perovskite films to further improve the performance and stability of perovskite solar cells.