Thallium lead iodide (TlPbI₃) single crystal inorganic perovskite: Electrical and optical characterization for gamma radiation detection

TlPbI₃ has been suggested as a candidate semiconductor material for room temperature gamma ray and charged particle detection, motivated by its wide bandgap (2.17–2.3 eV), and high density (6.6 gm/cm³) required for low noise and high intrinsic detection efficiency. In this work, we studied the optical and electronic properties of Bridgeman-grown TlPbI₃ single crystal using ultraviolet–visible–infrared absorption spectroscopy, low temperature cathodoluminescence, temperature dependent current-voltage measurements, and charge carriers’ mobility-lifetime measurements. The fabricated Ag/TlPbI₃/Ag device showed Ohmic behavior in temperatures ranging between −7 °C to 22 °C and exhibited high resistivity (~2 × 10¹¹ Ω.cm at RT). Fermi level pinning at 0.72 eV above valence band minimum or below conduction band maximum was calculated from the temperature dependent resistivity measurement, and the 2.17 eV bandgap was determined from ultraviolet–visible–infrared absorption spectroscopy. The cathodoluminescence spectrum of TlPbI₃ was resolved to two peaks at 1.45 eV and 1.48 eV indicating deep level traps. The mobility-lifetime product was estimated to be 3.43 × 10⁻⁵ cm²/V and 2.29 × 10⁻⁶ cm²/V for electrons and holes, respectively. Possible interpretations are presented suggesting the presence of vacancy type defects. Our results provide new essential information for developing such a new class of room temperature radiation detector material for a wide range of applications.