A Sustainable Approach Using Nanocrystals Functionalized Green Alkanes as Efficient Antisolvents to Fabricate High‐Quality Perovskite Films

Abstract To address the toxicity concern of extensively used chlorobenzene (CB) and toluene antisolvents, it is urgent to explore green and more efficient antisolvents. In this work, a general and highly reproducible methodology of employing CsPbI3 nanocrystals (NCs) functionalized green alkanes with ultralow‐polarity (Alkane/NCs) as antisolvents to fabricate high‐quality perovskite films is reported. Compared with the CB processed, the perovskite films with much improved quality and high‐orientation are achieved by the Alkane/NCs approach. NCs in the alkane antisolvents are proven to provide enough heterogeneous nuclei, solving effectively the discontinuous film problem encountered from using pure alkanes. Strikingly, the lattice anchoring effect of NCs accounts for the high‐orientation growth of the perovskite films as revealed directly by cryo‐electron microscopy (cryo‐EM). Moreover, the phase segregation that easily occur in the CB processed perovskite film is successfully suppressed by the Alkane/NCs method. The optimal device conversion efficiency is enhanced from 21.59% to 23.10% from CB to octane (OCT)/NCs. Impressively, the alkane/NCs processed perovskite films and their devices exhibit much improved stability over CB, with the conversion efficiency remaining at 94% of its initial value after 500 h light soaking for OCT/NCs device, while the CB device fails at around 100 h.