Soft-cover deposition of scaling-up uniform perovskite thin films for high cost-performance solar cells

Low-cost and high energy conversion efficiency are the crucial factors for large scale application of solar cells. In recent years, a promising high cost-performance photovoltaic technology, organometal halide perovskite solar cells (PSCs), has attracted great attention. However, most of the reported high efficiencies were obtained on a small working area of about 0.1 cm 2 with the material utilization ratio of only 1% during film deposition, which actually hinders the advancement in future application of PSCs. Here we present the soft-cover deposition (SCD) method where surface wettability, solution viscosity and thermal crystallization are the processing key factors for the deposition of uniform perovskite films with high material utilization ratios. Scaling-up, pinhole-free, large crystal grains and rough-border-free perovskite films were obtained over a large area of 51 cm 2 , which were processed continuously in ambient air with a significant enhancement in the material utilization ratio up to ∼80%. Highly reproducible power conversion efficiencies up to 17.6% were achieved in unit cells with a working area of 1 cm 2 , leading to a high overall cost-performance. We believe that the present SCD technology will benefit the low-cost fabrication of highly efficient perovskite solar cells and open up a route for the deposition of other solution processed thin-films. A large area perovskite film with less structural defects and a high material utilization ratio was formed by a continuous solution processing method, soft-cover deposition.