Composition engineering to enhance the photovoltaic performance and to prolong the lifetime for silver bismuth iodide solar cell

•Manipulation of bismuth ratio in Ag3BiI6 confers the film to have pore-free surface morphology.•Cation balance of Ag3BiI6 renders it to exhibit superior carrier mobility, film morphology, and light response.•Modified rudorffite solar cell of Ag3BiI6 can enhance its PCE around 30% and achieve 2.60%.•The unencapsulated devices can maintain 80% of initial PCE after 3,000 h stability test in an ambient condition (∼25°C and 35 RH%).