Scalable In‐Plane Directional Crystallization for The Printable Hole‐Conductor‐Free Perovskite Solar Cell Based on The Carbon Electrode

Abstract Popular solution‐processed approaches for producing the active layer of perovskite solar cells (PSCs) generally have to make compromise between crystallinity and compactness by inducing a rapid crystallization process with explosive nucleation and limited growth via removing solvent quickly. Here, a practical growth‐dominated in‐plane directional crystallization technique (IPDC) with a deeply retarded crystallization process for the scalable preparation of PSCs are reported. During the low‐temperature annealing, a tiny chamber with a small height is built atop the wet perovskite precursor film to restrain the vertical diffusion and removal of solvent vapor. The chamber eliminates the vertical solvent vapor gradient and induce a horizonal in‐plane gradient of solvent vapor pressure (SVP) toward the preset exhaust port which allows the slow escape of solvent vapor to outer space. In this way, nucleation is induced preferentially near the port and the as‐formed heterogeneous nuclei then grow continuously and directionally. With IPDC, sufficient filling of perovskite with high crystallinity and obvious growth orientation is realized in non‐ordered mesoporous scaffolds. An encouraging power conversion efficiency of 19.35% and 16.53% is achieved respectively for the 0.1 and 52.3‐cm 2 printable mesoscopic hole‐conductor‐free PSCs with carbon electrodes.