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(I0.6Br0.4)(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)& BULL;xNMP, & delta;-FAPbI(3)& BULL;xNMP, and PbI2 & BULL;xNMP. 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)& BULL;MACl & BULL;xNMP), 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.