Inorganic Halide Perovskitoid TlPbI₃ for Ionizing Radiation Detection

Room temperature semiconductor detector (RTSD) materials for γ-ray and X-ray radiation are in great demand for the nonproliferation of nuclear materials as well as for biomedical imaging applications. Halide perovskites have attracted great attention as emerging and promising RTSD materials. In this contribution, the material synthesis, purification, crystal growth, crystal structure, photoluminescence properties, ionizing radiation detection performance, and electronic structure of the inorganic halide perovskitoid compound TlPbI₃ are reported on. This compound crystallizes in the ABX₃ non-perovskite crystal structure with a high density of d = 6.488 g·cm^–3, has a wide bandgap of 2.25 eV, and melts congruently at a low temperature of 360 °C without phase transitions, which allows for facile growth of high quality crystals with few thermally-activated defects. High-quality TlPbI₃ single crystals of centimeter-size are grown using the vertical Bridgman method using purified raw materials. A high electrical resistivity of ≈10¹² Ω·cm is readily obtainable, and detectors made of TlPbI₃ single crystals are highly photoresponsive to Ag K_α X-rays (22.4 keV), and detects 122 keV γ-rays from ⁵⁷Co radiation source. The electron mobility-lifetime product µ_eτ_e was estimated at 1.8 × 10^–5 cm²·V^–1. A high relative static dielectric constant of 35.0 indicates strong capability in screening carrier scattering and charged defects in TlPbI₃.