In situ induced core/shell stabilized hybrid perovskites via gallium(III) acetylacetonate intermediate towards highly efficient and stable solar cells

Long-term stability of perovskite solar cells appears to be the bottleneck that limits its large-scale industrialization. Herein, we innovatively introduce gallium(III) acetylacetonate (GaAA3) as the precursor additive to in situ induce a metal–organic-complex monomolecular intermediate ([GaAA3]4), which allows to realize CsxFA1−xPbI3–[GaAA3]4 (0 < x < 1) hybrid perovskite materials. The formed hybrid perovskites are proven to possess a thus far unreported structure with CsxFA1−xPbI3 core and [GaAA3]4 shell, and the presence of thin [GaAA3]4 shells remarkably enhances the hydrophobicity of the perovskite thin films. As a result of an effective passivation effect by the core/shell heterostructure, the formed perovskites demonstrate superior photoelectronic performance in comparison with the independent archetype 3-dimensional (3D) counterparts, e.g., they show low defect-state density, strong luminescence, and long lifetime of photo-generation charge carriers, which finally result in a high power conversion efficiency of 18.24% for core–shell planar perovskite solar cells. Equally important, the stabilized power output (SPO) of the unencapsulated cell remains over 18% for 5 h in an adverse atmosphere with 50% relative humidity (RH). The present study provides a facile approach to fabricate core–shell perovskite solar cells with high efficiency and long-term stability against moisture.