Incubating High‐Quality Perovskite Film via Facial Mask Technique for Efficient and Stable Solar Cells

Abstract High‐performance perovskite film with superior internal and surface qualities is critical for perovskite solar cells (PSCs) but hardly achievable due to the rapid crystallization rate of perovskite itself. Herein, a novel technique by in situ manipulating perovskite crystal growth and modifying the surface properties is developed using organic passivating agent‐assisted polydimethylsiloxane membrane as a facial mask (FM) of perovskites. By placing the perovskite‐precursor films with their faces toward the designed FM during thermal annealing, a favorable microenvironment is constructed for incubating high‐quality perovskite films with smooth surface, enhanced vertical orientation of (100) plane, and well‐adjusted interfacial energy levels. With this versatile FM incubation technique, efficient PSCs for both methylammonium (MA)‐based and formamidinium (FA)‐MA‐Cs mixed perovskite systems are facilely fabricated, delivering excellent humidity/thermal stabilities and promising efficiencies up to 21.4% with an improved open‐circuit voltage of 1.15 V in MA‐based devices. This study not only provides a facile and efficient approach to rationally manage the perovskite growth process, but also reveals the fundamental characteristics of high‐quality perovskite films comprehensively for the construction of efficient and stable PSCs.