Intermediate Phase Formation and its Manipulation for Vacuum‐Assisted Blade‐Coated Wide‐Bandgap Perovskite

Large‐scale all‐perovskite tandem photovoltaic has raised more attention as the power conversion efficiency (PCE) of this device in a small area reaches 28%. However, the wide‐bandgap (WBG)‐perovskite (Cs 0.2 FA 0.8 Pb(I 0.6 Br 0.4 ) 3 ‐1.77 eV) fabrication on a large scale still faces difficulty in nucleation and crystallization control, leading to complicated intermediates and poor‐quality films. Through a systematic investigation of the vacuum‐assisted blade‐coated WBG perovskite film formation process, the origin for poor film quality is attributed to the numerous nucleation pathways under rapid vacuum pressure decrease, resulting in a mix in intermediates of (Cs,FA) 2 Pb 3 (I,Br) 8 · x NMP, δ ‐FAPbI 3 · x NMP, and PbI 2 · x NMP. To solve this problem, a proper additive MACl is selected and added. By lowering the formation energy of intermediate ((Cs,FA)Pb(I,Br) 3 ·MACl· x NMP), the nucleation and crystallization process is successfully modulated into a single way, resulting in a single‐orientation (100) film and an enhanced device performance of 16.75%, which is the champion PCE of blade‐coated 1.77 eV perovskite so far.