Highly Efficient Perovskite Solar Cells with Substantial Reduction of Lead Content

Despite organometal halide perovskite solar cells have recently exhibited a significant leap in efficiency, the Sn-based perovskite solar cells still suffer from low efficiency. Here, a series homogeneous CH₃NH₃Pb_(1-x)Sn_xI₃ (0 ≤ x ≤ 1) perovskite thin films with full coverage were obtained via solvent engineering. In particular, the intermediate complexes of PbI₂/(SnI₂)∙(DMSO)_x were proved to retard the crystallization of CH₃NH₃SnI₃, thus allowing the realization of high quality Sn-introduced perovskite thin films. The external quantum efficiency (EQE) of as-prepared solar cells were demonstrated to extend a broad absorption minimum over 50% in the wavelength range from 350 to 950 nm accompanied by a noteworthy absorption onset up to 1050 nm. The CH₃NH₃Pb_0.75Sn_0.25I₃ perovskite solar cells with inverted structure were consequently realized with maximum power conversion efficiency (PCE) of 14.12%.