“…[ 2 ] However, the stability is still one of the main problems for the performance of PSCs, which is related to the interface layer. [ 3 ] Although conventional organic hole transport layers (HTLs) (such as, poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate), 2,2′,7,7′‐tetrakis(N,N‐dipmethoxyphenylamine)‐ 9,9′‐spirobifluorene (Spiro‐MeOTAD), and poly(triarylamine)) have a well‐aligned valence band (VB) with perovskite, the simple solution preparation and deposition and high current density throughput, their low crystallization temperature, the weak interaction tendency with the perovskite, [ 4,5 ] and the doping process with hygroscopicity and deliquescence can result in a significant reduction in long‐term stability of these devices. Besides doping processing, [ 6 ] the passivation of the perovskite/HTL interface has been carried out successfully by varieties of interfacial engineering methods, such as 2D perovskite layers, [ 7 ] ligand‐based modification, [ 4,8 ] or even inorganic materials.…”