Growth of monolithically grained CH3NH3PbI3 film by a uniform intermediate phase for high performance planar perovskite solar cells

The growth of high-quality perovskite layers is dependent on the formed intermediate phases by an anti-solvent extraction technique. However, the intermediate phase formation is often not uniform due to the uncontrolled solvent extraction, and finally effects the perovskite layer growth. Here, a solvent-vapor-assisted post treatment is developed to obtain a homogeneous perovskite intermediate phase after anti-solvent extraction. The homogenization of the intermediate phase renders the sole upward growth mechanism of perovskite crystals during heating, affording optimal alignment with few horizontal grain boundaries and large grains. These coarsened grains across the whole perovskite film facilitate efficient carrier transport and reduce charge recombination. As a result, the resulting planar perovskite solar cell (PeSC) has achieved a power conversion efficiency of 18.3%, compared to the as-prepared PeSC of 15.7%. Via solvent-vapor-assisted treatment, the operating time window of anti-solvent extraction was prolonged significantly, and correspondingly, a narrowed efficiency distribution was obtained. Thus, the influence of the operating time on the cell efficiency is released, effectively promoting the operability of practical applications. (C) 2018 Elsevier B.V. All rights reserved.