Sn-based perovskite solar cells are attracting great attention because of their potential for efficiency enhancement and their relative eco-friendliness compared with Pb-based perovskite solar cells. The main challenges lie in improving the oxidation stability and ensuring a uniform morphology of the Snbased perovskite films. Here, we introduce a bilayer structure of 2D PEA 2 SnI 4 and 3D MASnI 3 perovskite (PEA = phenethylammonium; MA = methylammonium) formed by a sequential vapor process that combines vacuum deposition and vapor reaction. The vapor process ensures that the perovskite thin films are uniform and enables the fabrication of an upper layer with fine thickness control without damaging the lower layer. With the introduction of the 2D layer, Sn oxidation is suppressed and the crystallinity of the 3D layer is enhanced. A planar-type solar cell fabricated using the optimized 2D/3D structure exhibits an average efficiency of 9.2 ± 0.2%.

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High-quality and reproducible perovskite layer fabrication routes are essential for the implementation of efficient planar solar cells. Here, we introduce a sequential vapor-processing route based on physical vacuum evaporation of a PbCl2 layer followed by chemical reaction with methyl-ammonium iodide vapor. The demonstrated vapor-grown perovskite layers show compact, pinhole-free, and uniform microstructure with the average grain size of ~ 320 nm. Planar heterojunction perovskite solar cells are fabricated using TiO2 and spiro-OMeTAD charge transporting layers in regular n-i-p form. The devices exhibit the best efficiency of 11.5% with small deviation indicating the high uniformity and reproducibility of the perovskite layers formed by this route.Electronic supplementary materialThe online version of this article (10.1186/s11671-017-2401-5) contains supplementary material, which is available to authorized users.

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