Novel zero-dimensional halide perovskite Li2Hf(Br,I)6 with red/NIR emission wavelength for thermal neutron detection

Novel neutron Li 2 Hf(Br,I) 6 scintillators were developed, and their luminescence and scintillation properties were investigated both experimentally and via density functional theory calculations. The development of conventional neutron scintillators has been dominated by materials with emission wavelengths in the range of 400–500 nm that have wavelength sensitivity of photomultiplier tubes (PMTs). However, with the recent emergence of detectors having higher quantum efficiencies than PMTs, such as Si-based photodetectors, there is a need for neutron scintillators with red-to-near-infrared (NIR) emission wavelengths that match the wavelength sensitivity of these detectors. Therefore, this study demonstrates that Li 2 Hf(Br,I) 6 exhibits self-trapped exciton emission under both X-ray and thermal neutron irradiation, with an emission peak at approximately 650 nm, which is 100–200 nm longer than the corresponding peak wavelength of conventional neutron scintillators. The emission wavelength of Li 2 Hf(Br,I) 6 matches the wavelength sensitivity of Si-APD. In addition, Li 2 HfBr 4 I 2 is the first neutron scintillator to combine emission in the NIR region with a high light output of approximately 40,000 photons per thermal neutron, which is six to seven times that observed in commercial Ce:Li-glass (GS20). Furthermore, the pulse shape discrimination (PSD) Figure of Merit (FOM) was found to be 2.47, indicating excellent neutron/gamma-ray discrimination capability. This study opens a new avenue for both red/infrared emission and high-light-output neutron scintillators. • Li 2 Hf(Br,I) 6 is a new family of halide single crystal scintillators. • Li 2 HfBr 4 I 2 exhibits self-trapped exciton (STE) luminescence at 650 nm. • DFT reveals I-substitution lowers the band gap, causing 650 nm STE emission. • Li 2 HfBr 4 I 2 shows the highest light output among red-emitting neutron scintillators. • Excellent neutron/gamma-ray (n/γ) discrimination capability was demonstrated.