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

Abstract 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 (FAPbBr ₃ ) 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 FAPbBr ₃ single crystals without any trapped solvent molecules in the lattices. The FAPbBr ₃ single crystals exhibited a tenfold reduction in bulk charge recombination rate, and this enabled the FAPbBr ₃ gamma‐ray spectrometer to achieve an energy resolution of 1.47 ± 0.05% for 662 keV ¹³⁷ Cs gamma rays, which is the best among solution‐grown semiconductor detectors. The unencapsulated FAPbBr ₃ gamma‐ray spectrometer exhibited more than three months of operational and storage stability.