BA2XBr4 (X = Pb, Cu, Sn): from lead to lead-free halide perovskite scintillators

Abstract

Solution-processed hybrid organic–inorganic lead halide perovskites have potential for next generation X-ray imaging applications. Here, we discuss the effect of Pb replacement by Cu or Sn on the optical and scintillation properties of the high-light-yield and fast crystal scintillators of BA₂PbBr₄. By replacing Pb with Cu or Sn, the measured bandgap shifts from 3.59 to 3.90 and 3.44 eV, while the photoluminescence decay time slows down from 3.0 ns to 1.3 and 8.5 μs, respectively. The bandgaps and the structures are also validated by density functional theory calculations. Although BA₂CuBr₄ and BA₂SnBr₄ have large Stokes shifts of 2.06 and 1.13 eV, respectively, both crystals show no radioluminescence (RL) at room temperature (RT). Temperature-dependent RL measurements demonstrate that BA₂PbBr₄ has negative thermal quenching, while Pb replacement by Cu or Sn results in strong thermal quenching, affecting the light yields at RT. Despite slow decay times and low light yields for BA₂CuBr₄ and BA₂SnBr₄, this study opens new understanding for lead-free perovskite crystals and the trends in their scintillation properties.