Zero‐Dimensional Gua3SbCl6 Crystals as Intrinsically Reabsorption‐Free Scintillators for Radiation Detection

The search for efficient, re‐absorption‐free scintillators has recently focused the attention on antimony‐based halides, which exhibit largely Stokes shifted luminescence due to radiative recombination of excitons self‐trapped (STE) in strongly Jahn–Teller distorted Sb3+ color centers. Here, the synthesis of a hybrid structure is reported with chemical formula (C13H14N3)3SbCl6 consisting of spatially isolated [SbCl6]3− octahedra separated by organic N,N'‐diphenylguanidinium (Gua) molecules. The optical properties of this material are mainly determined by the inorganic component and are characterized by a pronounced Stokes shift of ≈1.3 eV and a room‐temperature photoluminescence (PL) efficiency of up to 85%. Remarkably, highly efficient radioluminescence (RL) is observed with scintillation light yields of ≈2000 ph MeV−1 using both soft X‐rays and a 124 keV gamma source. Temperature‐dependent PL and RL measurements confirm the minor role of non‐radiative channels, which are completely suppressed below 100 K. Thermally stimulated luminescence measurements suggest that the traps in Gua3SbCl6 crystals have a significantly large energy depth distribution below the absorbing state. Here, the optical and scintillation properties of Gua3SbCl6 hybrid crystals are reported, which exhibit largely Stokes‐shifted emission under both optical and ionising excitation (ФPL > 85%, LY ≈ 2 × 103 ph MeV−1) and good radiation hardness to high gamma‐ray doses (1 MGy). Complementary experiments with synchrotron light, X‐rays and 57Co γ‐rays, together with T‐dependent time‐resolved PL measurements, reveal the origin of their luminescence and identify the residual non‐radiative recombination channels quenched at cryogenic temperatures (T