Viscosity Blending Approach for 22.42% Efficient Perovskite Solar Cells

Abstract

We report here the viscosity blending approach toward high efficiency perovskite solar cells. A binary solvent is introduced in the precursor solution, where 2-methoxyethaol (2ME) is mixed with dimethylformamide (DMF) or dimethylacetamide (DMAc). Viscosity of the binary solvent system is estimated by calculating the viscosity blending number. For the ratio of DMF (DMAc): 2ME = 75:25 leading to the viscosity of 1.0317 (1.1699) cSt, a forward-scanned power conversion efficiency (PCE) of 22.42% is achieved along with photocurrent density of 25.46 mA/cm2, voltage of 1.122 V and fill factor of 0.785, which is higher than the PCE of 20.59% for the single DMF solvent. The binary solvent with optimal viscosity is found to be beneficial to reducing trap density and improving carrier lifetime even in thicker perovskite film. © 2021 Korean Chemical Society, Seoul & Wiley-VCH GmbH