Superwetting Nanofluids of NiO <sub>x</sub> ‐Nanocrystals/CsBr Solution for Fabricating Quality NiO <sub>x</sub> ‐CsPbBr <sub>3</sub> Gradient Hybrid Film in Carbon‐Based Perovskite Solar Cells
Zengyi Wang, Lele Zhang, Xuanling Liu, Lin Ye, Shuang Zhao, Yingyu Chen, Huiyu Yan, Jianhua Han, Hong Lin
Abstract
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 (NiO x ) nanocrystals (NCs)‐CsBr solution are first utilized to fabricate quality NiO x ‐CsPbBr 3 hybrid film with gradient‐distributed NiO x 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 NiO x ‐CsPbBr 3 hybrid film are improved after incorporating NiO x NCs into CsPbBr 3 . This originates from the superb wettability of NiO x ‐CsBr NFs on substrates and the excellent hole‐transport properties of NiO x . Consequently, the C‐PSCs with the structure of FTO/SnO 2 /NiO x ‐CsPbBr 3 /C displays a power conversion efficiency of 10.07%, resulting in a 23.6% improvement as compared with the pristine CsPbBr 3 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.