Room‐Temperature Meniscus Coating of >20% Perovskite Solar Cells: A Film Formation Mechanism Investigation

Perovskite solar cells (PSCs) are ideally fabricated entirely via a scalable solution process at low temperatures to realize the promise of simple manufacturing, low‐cost processing, compatibility with flexible substrates, and perovskite‐based tandem solar cells. However, high‐quality photoactive perovskite thin films under those processing conditions is a challenge. Here, a laminar air‐knife‐assisted room‐temperature meniscus coating approach that enables one to control the drying kinetics during the solidification process and achieve high‐quality perovskite films and solar cells is devised. Moreover, this approach offers a solid model platform for in situ UV–vis and microscopic investigation of the perovskite film drying kinetics, which provide rich insights correlating the degree of supersaturation, the nucleation, and growth rate during the kinetic drying process, and ultimately, the film morphology and performance of the solar cell devices. Manufacturing friendly, antisolvent‐free room‐temperature coating of hysteresis‐free PSCs with a power conversion efficiency of 20.26% for 0.06 cm2 and 18.76% for 1 cm2 devices is demonstrated. Through a laminar air‐knife‐assisted room‐temperature meniscus coating, assisted by in situ UV–vis and microscopes, fundamental mechanisms of perovskite nucleation and crystal growth are investigated. Upon in‐depth film formation understanding, hysteresis‐free perovskite solar cell with a power conversion efficiency of 20.26% for 0.06 cm2 and 18.76% for 1 cm2 devices are successfully demonstrated by manufacturing a friendly room‐temperature meniscus coating process.