Printable and Homogeneous NiOx Hole Transport Layers Prepared by a Polymer‐Network Gel Method for Large‐Area and Flexible Perovskite Solar Cells

Abstract As one of the most promising hole transport layers (HTLs), nickel oxide (NiO x ) has received extensive attention due to its application in flexible large‐area perovskite solar cells (PSCs). However, the poor interface contact caused by inherent easy‐agglomeration phenomenon of NiO x nanoparticles (NPs) is still the bottleneck for achieving high‐performance devices. Herein, a general strategy to synthesize NiO x NPs with high crystallinity and good dispersibility via the polymer network micro‐precipitation method is reported. Promisingly, this approach realizes the flow‐division of precipitant and the restraint of the NPs motion, thereby effectively alleviating the coagulation phenomenon caused by excessive local concentration and secondary movement adsorption. Furthermore, the addition of ionic liquid not only inhibits the secondary aggregation of NiO x NPs during the dispersion process, but also significantly enhances the properties of the colloidal solution. Ultimately, the 1.01 cm 2 PSCs based on the optimized NiO x HTLs achieve the champion power conversion efficiency of 20.91% and 19.17% on rigid and flexible substrates, respectively. Moreover, the reproducibility and stability of PSCs are also significantly improved, especially for flexible devices. Overall, this strategy provides the possibility for flexible, large‐area fabrication of high‐quality NiO x HTLs to promote the development of stable and efficient perovskite devices.