Crystallization Regulation by Introducing Multistage Growth Template Enables Efficient and Stable Inverted Perovskite Solar Cells

Abstract

The non-homogeneity of nickel oxide (NiOx) nanoparticles (NPs) and the problematic interlayer interconnectivity with perovskite film are the current major bottlenecks for the further development of corresponding perovskite solar cells (PVSCs). Herein, a multistage growth template strategy is proposed to successively ameliorate the crystallization kinetics of NiOx NPs and perovskite film by modulating the intermolecular forces in nickel precursor solutions and the interfacial interactions of NiOx/perovskite, respectively. The incorporated multifunctional imidazole tetrafluoroborate ([CnMIM]BF4) ionic liquids (ILs) can initially serve as soft template for NiOx growth, and altering the alkyl chain length achieves the controllable sizes and tunable electronic structures of NiOx NPs. Meanwhile, the excellent solution dispersibility of ILs-optimized NiOx owing to the electrostatic and steric-hindrance effects allows for good printability. Specially, the interface adherent ILs can subsequently regulate the Gibbs free-energy of perovskites nucleation and provide the growth sites to assist high-quality crystallization for obtaining homogeneous perovskite film with excellent interfacial interconnectivity. Resultantly, the unencapsulated PVSCs displays an impressive efficiency of 25.73%, and superior stability which maintaining over 80% of initial efficiencies after 800 h of storage in N2 at 85 °C or 1400 h of aging in air with 40-50% relative humidity.