In-situ secondary annealing treatment assisted effective surface passivation of shallow defects for efficient perovskite solar cells

The interfacial defects passivation of perovskite is one of the most effective approaches to realize highly efficient and stable perovskite solar cells (PSCs). Herein, we propose an easy in-situ secondary annealing method by using a quaternary ammonium salt tetraethylammonium hexafluorophosphate (TEAH) to enhance the photovoltaic performance and device stability. The research manifests that TEAH can homogeneously distribute on the perovskite surface, and effectively passivate the surface and boundary defects. Correspondingly, the hole extraction from perovskite to the hole transport layer (HTL) is greatly improved, hindering the non-radiative charge carrier recombination. With the introduction of TEAH treatment, the power conversion efficiency (PCE) of the PSC has been elevated from 18.57% to 20.25%, with well suppressed hysteresis. Moreover, the exposed hydrophobic ethyl-terminal groups of TEAH can protect perovskite film from degradation by ambient moisture in some extent. As a result, TEAH treated PSC exhibits good stability, retaining 74.1% of its initial PCE after 680 h aging under ambient air with a relative humidity (RH) of 55–60%. [Display omitted] •An in-situ secondary annealing treatment assisted surface passivation method is proposed.•The chelating between TEAH with Pb2+ improves the perovskite film quality and passivates the surface defects.•The open-circuit voltage and device stability are improved with tetraethylammonium hexafluorophosphate treatment.