Perovskite solar cells (PSCs) with solution-based fabrication processes deserve a simple and controllable fabrication process to produce cost-effective new-generation solar cells. Increasing optoelectrical properties of the light-harvesting perovskite layer during the fabrication process is used to enhance photovoltaic efficiency and the stability of PSCs. Here, ellagic acid was added into the lead iodide precursor to control the reaction of lead iodide with formamidinium iodide to generate a perovskite layer with enlarged grains. The obtained results showed the ellagic acid additive reduced charge recombination losses within solar cells and prompted charge transfer from perovskite to electron transporting layer and hole transporting layer, recording a champion efficiency of 22.04 % along with an open circuit voltage of 1.095 V, short-circuit current density of 24.17 mA cm−2, and fill factor of 78.94 %. In addition, the ellagic acid-based PSCs showed considerable stability improvement against the humidity and light irradiance compared to the control PSCs. It can be concluded that the ellagic acid additive may push the PSCs further to commercialization.