Insight into Charge Carrier Recombination Mechanisms in Lead Based Mixed Cation and Halide Perovskite

Charge recombination dynamics inside a Cs(0.05)FA(0.80)MA(0.15)PbI(2.75)Br(0.25) perovskite film were studied by employing picosecond -microsecond transient absorption spectroscopy. A wide range of excitation intensity from 0.18 to 127 mu J cm( -2) revealed two different charge recombination mechanisms. The charge recombination occurs in the 1st order with the excitation intensity of <2 J cm (-2) , while with the higher excitation intensity of >2 mu J cm (-2 ), the recombination occurs in the addition of the 2nd order. The analysis of the 1(st) order reactions revealed that trap states with at least 3 different potential levels exist in the Cs(0.05)FA(0.80)MA(0.15)PbI(2.75)Br(0.25) perovskite film. From the transition of the reaction order from the 1(st) to the 2(nd ), the trap density inside the perovskite film is evaluated to be 1 x 10(17) cm (-3).