Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH₂)₂PbX₃ (FAPbX₃), it has been considered to be a better optoelectronic material than conventional CH₃NH₃PbX₃ (MAPbX₃). Herein, we fabricated a FAPbBr₃ microcrystal-based photodetector that exhibited a good responsivity of 4000 A W⁻¹ and external quantum efficiency up to 10⁶% under one-photon excitation, corresponding to the detectivity greater than 10¹⁴ Jones. The responsivity is two orders of magnitude higher than that of previously reported formamidinium perovskite photodetectors. Furthermore, the FAPbBr₃ photodetector’s responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W⁻¹, which is four orders of magnitude higher than that of its MAPbBr₃ counterparts. The response time of this photodetector is less than 1 ms. This study provides solid evidence that FAPbBr₃ can be an excellent candidate for highly sensitive and fast photodetectors.

Both trap-state densities and energy levels affect carrier transfer, resulting in a maximum diffusion length of 380 μm in CH₃NH₃PbI_3−xCl_x(x= 0.005).