Efficient inverted all inorganic CsPbI3 planar solar cells via twice-coating in air condition

Recently, solar cells based on inorganic cesium lead triiodide perovskite materials have received considerable attention. However, the quality and thickness of perovskite films are still out from satisfaction due to the limited solubility of the precursor materials. Here, a simple twice-coating process is reported for fabrication of high quality perovskite films in a complete air condition. Defects such as pinholes, can be effectively eliminated by the second coating with further growth of the grain sizes, thus greatly suppressing charge recombination in these perovskite films. Furthermore, the improved film thickness can ameliorate the absorption of incident light. In consequence, the power conversion efficiency of 11.05% with comprehensively improved device parameters is obtained in traditional inverted planar perovskite solar cells, with a dramatic increase of 42% being compared with the control device (7.83%). In addition, the device's stability is also improved due to such high quality twice-coated perovskite films. The results reveal that such twice-coating technique is a promising choice for high-stablilty and efficient perovskite solar cells.