Crystallization Control Assists Annealing‐Free Fabrication of Printable Mesoscopic Perovskite Solar Cells with PCE Over 17%

The one‐step drop‐casting for preparing perovskite films in three‐layer mesoporous for printed mesoscopic perovskite solar cells always results in insufficient filling of mesopores. A binary solvent based on 2‐methoxyethanol and 1‐methyl‐2‐pyrrolidone offers a method suitable for room‐temperature, annealing‐free to prepare dense perovskite films in mesopores. The crystallization process of perovskite films in mesopores can be adjusted by the content of NMP in the solvent. Time‐of‐flight secondary ion mass spectrometry and cross‐sectional scanning electron microscopy results demonstrate that the introduction of NMP enhances the density of the perovskite film based on the binary solvent system, optimizing the contact between the perovskite film and the mesoporous scaffold. When the ratio of 2‐methoxyethanol to 1‐methyl‐2‐pyrrolidone is 9:1, the optimal device achieves impressive performance metrics, including a power conversion efficiency of 17.28%, an open‐circuit voltage of 0.98 V, a short‐circuit current of 23.80 mA cm‐2, and a fill factor of 74.08%. This represents the highest power conversion efficiency achieved to date in the room‐temperature, anneal‐free preparation of perovskite films for printable mesoscopic perovskite solar cells. Furthermore, devices based on this binary solvent system exhibit remarkable stability, with almost no loss in efficiency even after 120 days of storage in an air environment without encapsulation.This article is protected by copyright. All rights reserved.