Super hydrophilic, ultra bubble repellent substrate for pinhole free Dion–Jacobson perovskite solar cells

The progress in efficiency improvements of blade-coated two-dimensional perovskite solar cells (PSCs) lags behind that of spin-coated ones. Pinholes and voids are two important structural defects hiding in blade-coated large-area perovskite films to deteriorate device efficiency and stability. However, the formation of pinholes and voids is still difficult to predict. On substrates with moderate wettability, Dion–Jacobson perovskite films can be blade-coated with good coverage, but we highlight that the formation of nanoscale voids buried at the bottom side of perovskite films can occur frequently, depending critically on the wettability of substrates. It is revealed that super hydrophilic NiOx substrates with contact angle θ < 5° possesses strong bubble repellent property, which thermal dynamically prevents the retraction of precursor solution and plays an important role to suppress the attachment and growth of bubbles on its surface. The probabilities of forming both pinholes and buried voids in perovskite films on super hydrophilic NiOx substrates are one order of magnitude lower than that on hydrophilic PTAA and poly-TPD substrates. The blade-coated (BDA)MA4Pb5I16 films on NiOx substrate offer PSCs with excellent interfacial hole extraction and reduced leakage current, contributing a significant power conversion efficiency improvement from ∼10% to 16.26%.