The Influence of Solvent Permittivity and Polarity on Solution-Based Perovskite Synthesis

Abstract The choice of solvents in solution-based perovskite synthesis critically influences precursor solubility, crystallization pathways, and final film morphology, with direct consequences for the performance and stability of perovskite solar cells (PSCs) and optoelectronic applications. This review examines the roles of two key macroscopic solvent properties—dielectric constant (permittivity) and polarity—in guiding perovskite film and nanocrystal formation across various deposition strategies. High-permittivity solvents enhance precursor solvation and intermediate phase stability but may also induce lattice degradation and ligand stripping in post-treatment steps. In contrast, moderate-permittivity solvents often promote larger grain sizes, improved crystallinity, and superior optoelectronic performance, particularly in sequential deposition techniques. Solvent polarity affects wetting behavior, diffusion dynamics, and surface interactions, where moderately polar systems provide a balance between nucleation control and defect passivation. The review further discusses how solvent-induced variations in film morphology correlate with photovoltaic/optoelectronic performance and long-term device stability. While additional parameters such as donor number and hydrogen bonding capabilities refine solvent selection, permittivity and polarity represent accessible and practically relevant descriptors that can complement other solvent parameters in guiding solvent engineering. Overall, this work underscores the importance of rational solvent design in achieving high efficiency, stability, and scalable perovskite optoelectronic devices.