Melt-grown large-sized Cs2TeI6 crystals for X-ray detection

Abstract

Herein, we report the details of the synthesis and crystal growth of a lead-free perovskite derivative Cs₂TeI₆ crystal, which reveals long-term environmental stability. The synthesis process is optimized to obtain pure Cs₂TeI₆ polycrystals, and to eliminate the formation of residual CsI resulting from high vapor pressure. Subsequently, the Cs₂TeI₆ single crystal with dimensions of Φ10 mm × 55 mm is grown by the vertical Bridgman method. The as-grown 0-D structural Cs₂TeI₆ crystal exhibits a high resistivity of 9.92 × 10¹¹ Ω cm, and resulting mobilities of 4.03 ± 0.33 cm² V⁻¹ s⁻¹ and 9.40 ± 0.45 cm² V⁻¹ s⁻¹ for electrons and holes, respectively. The Au/Cs₂TeI₆/Au device shows a good response for optoelectronic and X-ray detection, with a relatively high X-ray sensitivity of 27.8 μC Gy⁻¹ cm⁻² and a low detection limit of 72.5 nGy s⁻¹.