Elegant Face-Down Liquid-Space-Restricted Deposition of CsPbBr Films for Efficient Carbon-Based All-Inorganic Planar Perovskite Solar Cells.

It is a great challenge to obtain the uniform films of bromide-rich perovskites such as CsPbBr in the two-step sequential solution process (two-step method), which was mainly due to the decomposition of the precursor films in solution. Herein, we demonstrated a novel and elegant face-down liquid-space-restricted deposition to inhibit the decomposition and fabricate high-quality CsPbBr perovskite films. This method is highly reproducible, and the surface of the films was smooth and uniform with an average grain size of 860 nm. As a consequence, the planar perovskite solar cells (PSCs) without the hole-transport layer based on CsPbBr and carbon electrodes exhibit enhanced power conversion efficiency (PCE) along with high open circuit voltage ( V). The champion device has achieved a PCE of 5.86% with a V of 1.34 V, which to our knowledge is the highest performing CsPbBr PSC in planar structure. Our results suggest an efficient and low-cost route to fabricate the high-quality planar all-inorganic PSCs.