Viscosity Blending Approach for 22.42% Efficient Perovskite Solar Cells

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/cm 2 , 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.