Bulk Charge Recombination Reduction Enabled High Spectral Resolution Perovskite Gamma-Ray Spectrometer

Solution-grown metal halide perovskite single crystals have been demonstrated as potential gamma-ray spectrometer. However, the energy resolution of the solution-grown formamidinum lead bromide (FAPbBr₃) single crystal spectrometer still suffers from strong bulk charge recombination. Here, it is identified that the high bulk charge recombination arises from a gradient Type-I band distribution throughout the crystal. This band distribution is attributed to the strong coordination of solvents with FA⁺ cations, which become incorporated into the perovskite lattice during crystal growth. It is selected a solvent that more easily decomplexed with FA⁺, and successfully obtained FAPbBr₃ single crystals without any trapped solvent molecules in the lattices. The FAPbBr₃ single crystals exhibited a tenfold reduction in bulk charge recombination rate, and this enabled the FAPbBr₃ gamma-ray spectrometer to achieve an energy resolution of 1.47 ± 0.05% for 662 keV ¹³⁷Cs gamma rays, which is the best among solution-grown semiconductor detectors. The unencapsulated FAPbBr₃ gamma-ray spectrometer exhibited more than three months of operational and storage stability.