Effect of bromine on the formation of δ-CsPbI3 in Cs0.22FA0.78Pb(I1-xBrx)3 perovskite solar cells

Applying Cs(x)FA(1-x)PbI(3 )perovskite is a useful strategy for synthesizing high-efficiency organic-inorganic lead halide perovskite solar cells because it improves the stability of the perovskite structure. High concentration of cesium (Cs) in CsFAPbI3 synthesized under ambient conditions typically lead to phase separation due to S-CsPbI3 formation and moisture, thereby reducing light absorption and increasing non-radiative recombination. To counter this, we fabricated the mixed halide Cs(0.22)FA0.78Pb(I1-xBrx)(3) perovskite films. Introducing bromine (Br) content effectively reduced the S-CsPbI3 formation and grain boundaries, thus suppressing the non-radiative recombination between perovskite and charge transport layers. Employing this approach, our perovskite solar cells with a 10 % Br concentration achieved a power conversion efficiency of 15.81 %. This demonstrates the potential of Br incorporation in enhancing the stability and efficiency of perovskite solar cells.