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FEB 3Abstract:
The detection of γ-rays at room temperature with high-energy resolution using semiconductors is one of the most challenging applications. The presence of even the smallest amount of defects is sufficient to kill the signal generated from γ-rays which makes the availability of semiconductors detectors a rarity. Lead halide perovskite semiconductors exhibit unusually high defect tolerance leading to outstanding and unique optoelectronic properties and are poised to strongly impact applications in photoelectric conversion/detection. Here we demonstrate for the first time that large size single crystals of the all-inorganic perovskite CsPbCl3 semiconductor can function as a high-performance detector for γ-ray nuclear radiation at room temperature. CsPbCl3 is a wide-gap semiconductor with a bandgap of 3.03 eV and possesses a high effective atomic number of 69.8. We identified the two distinct phase transitions in CsPbCl3, from cubic (Pm-3m) to tetragonal (P4/mbm) at 325 K and finally to orthorhombic (Pbnm) at 316 K. Despite crystal twinning induced by phase transitions, CsPbCl3 crystals in detector grade can be obtained with high electrical resistivity of ~1.7 X 109 Ω·cm. The crystals were grown from the melt with volume over several cubic centimeters and have a low thermal conductivity of 0.6 W m-1 K-1. The mobilities for electron and hole carriers were determined to ~30 cm2/(V s). Using photoemission yield spectroscopy in air (PYSA), we determined the valence band maximum at 5.66 ± 0.05 eV. Under gamma-ray exposure, our Schottky-type planar CsPbCl3 detector achieved an excellent energy resolution (~16% at 122 keV) accompanied by a high figure-of-merit hole mobility-lifetime product 3.2 x 10-4 cm2/V and a long hole lifetime (16 μs). The results demonstrate considerable defect tolerance of CsPbCl3 and suggest its strong potential for γ-radiation and X-ray detection at room temperature and above.
