New Scalable Cold-Roll Pressing for Post-treatment of Perovskite Microstructure in Perovskite Solar Cells

We introduce a new cold-roll pressing technique to enhance microstructure of deposited pinholed perovskite layers in perovskite solar cells. This technique is proposed as an efficient post-treatment method for deposited perovskite layers that are mainly suffering from excessive number of pinholes. In this regard, we followed a set of sequential steps of partial dissolving the perovskite layer surface and a cold-roll pressing to compress and spread the semidissolved portion of the perovskite that is exposed to slight N, N -dimethylformamide (DMF) vapor. Because of applying no heating during the compressing process, the cells showed good stability against decomposition. Transformation of perovskite layer from columnar microstructures containing a large amount of uncoated TiO 2 surface to a continuous and approximately pinhole-free structure resulted in an increase in the power conversion efficiency (PCE) of the cells from 8.16 to 13.24%, showing a 62% enhancement in the cell performance. For cell performance enhancement observed in this study, we can propose three considerable explanations: drop of the recombination regions, increasing the visible light absorbance, and the increase in contact surface between perovskite and TiO 2 layer.