Superwetting Nanofluids of NiO_x‐Nanocrystals/CsBr Solution for Fabricating Quality NiO_x‐CsPbBr₃ Gradient Hybrid Film in Carbon‐Based Perovskite Solar Cells

Abstract

The wettability of precursor solution on substrates is the critical factor for fabricating quality film. In this work, superwetting nanofluids (NFs) of non‐stoichiometric nickel oxide (NiOx) nanocrystals (NCs)‐CsBr solution are first utilized to fabricate quality NiOx‐CsPbBr3 hybrid film with gradient‐distributed NiOx NCs in the upper part for constructing hole transport ladder in carbon‐based perovskite solar cells (C‐PSCs). As anticipated, the crystalline properties (improved crystalline grain diameters and reduced impurity phase) and hole extraction/transport of the NiOx‐CsPbBr3 hybrid film are improved after incorporating NiOx NCs into CsPbBr3. This originates from the superb wettability of NiOx‐CsBr NFs on substrates and the excellent hole‐transport properties of NiOx. Consequently, the C‐PSCs with the structure of FTO/SnO2/NiOx‐CsPbBr3/C displays a power conversion efficiency of 10.07%, resulting in a 23.6% improvement as compared with the pristine CsPbBr3 cell. This work opens up a promising strategy to improve the absorber layer in PSCs by incorporating NCs into perovskite layers through the use of the superwettability of NFs and by composition gradient engineering.