Co-passivation of perovskite film towards stable and efficient perovskite solar cell

Inverted perovskite solar cells (PSCs) have attracted tremendous attention due to their compatibility in flexible and tandem devices, thus with great commercialization potential. However, abundant crystal defects and energy level mismatch still remain throughout the devices, which cause nonradiative recombination and become the two main issues impeding the performance that need to be solved urgently. In this work, we have adopted a co-passivation strategy by incorporating PEACl (phenethylammonium chloride) into perovskite films and adding PPF (2,8-Bis(diphenyl-phosphoryl)-dibenzo[b,d]furan) in anti-solvent. It is found that PEACl could significantly passivate the defects in the perovskite bulk and grain boundaries. PPF could reinforce the passivation efficacy by forming coordination bond between PPF and Pb2+ (P=O→Pb). It also forms a thin n-type hole-blocking layer between perovskite film and electron transport layer, which increases photo-generated charge carrier lifetimes and decreases nonradiative recombination at carrier transport interfaces. Furthermore, after being co-passivated with PEACl and PPF (PEACl/PPF treated), an energy level gradient is formed between the perovskite and passivated layer, which is conducive to electron extraction and hole blocking, further resulting in less energy loss in the charge transfer process. As a result, the PEACl/PPF treated device obtained a power conversion efficiency (PCE) of 22.70% with an impressive open-circuit voltage (Voc) of 1.19 V, much higher than the corresponding values (19.51% and 1.06 V) of the control device.