Uncoordinated lead in perovskites is a critical factor affecting solar cells’ performance. It readily forms deep-level defects acting as non-radiative recombination centers

detrimental to power conversion efficiency. This work employs a synergistic passivation strategy using 12-crown-4 and phenethylammonium iodide at the interface between the wide-bandgap perovskite and the electron transport layer

addressing the insufficient passivation of uncoordinated lead defects by a single passivator. Results demonstrate that both phenethylammonium iodide and 12-crown-4 provide electrons to coordinate lead on the perovskite surface. However

synergistic passivation yields significantly greater gains in power conversion efficiency compared with either single passivator. It reduces non-radiative recombination

leading to increased steady-state photoluminescence intensity and prolonged transient carrier lifetime

consequently enhancing the open-circuit voltage. Furthermore

synergistic passivation increases recombination resistance and reduces series resistance

thereby improving the fill factor

without altering the perovskite structure or morphology. Based on this strategy

inverted wide-bandgap perovskite solar cells fabricated with the synergistic passivation achieved an efficiency of 21.63%

demonstrating great potential for high-efficiency perovskite tandem cells.