Solvent–precursor interaction engineering for formamidinium-based perovskites: Role of dimethylacetamide, N-methyl-2-pyrrolidone, and methylammonium chloride in film formation and device performance

Abstract

In the solution-processing method of perovskites, selecting appropriate solvents for each precursor is crucial for synthesizing homogeneous perovskite films, as the interaction energy and mechanism between each solvent and precursor vary significantly. In this study, we used dimethylacetamide (DMAc) as the host solvent instead of dimethylformamide to match the Hansen solubility parameters (HSP) with N-methyl-2-pyrrolidone (NMP) and anti-solvent. DMAc-based perovskite facilitates the formation of intermediate phase with NMP due to well-matched HSP, resulting in formation of a glossy perovskite film. However, the power conversion efficiency (PCE) of DMAc-based perovskite solar cells did not improve, primarily because of the formation of small grains. Although methylammonium chloride (MACl) was introduced as an additive to promote grain growth, no significant enhancement in the PCE was observed, likely due to the low interaction energy between MACl and NMP. These findings enhance our understanding of solvent-precursor interactions by applying HSP theory and MACl additive.