Band-Edge Engineering To Eliminate Radiation-Induced Defect States in Perovskite Scintillators.

Under radiative environments such as extended hard X- or γ-rays, degradation of scintillation performance is often due to irradiation-induced defects. To overcome the effect of deleterious defects, novel design mitigation strategies are needed to identify and design more resilient materials. The potential for band-edge engineering to eliminate the effect of radiation-induced defect states in rare-earth-doped perovskite scintillators is explored, taking Ce-doped LuAlO as a model material system, using density functional theory (DFT)-based DFT + and hybrid Heyd-Scuseria-Ernzerhof (HSE) calculations. From spin-polarized hybrid HSE calculations, the Ce activator ground-state 4f position is determined to be 2.81 eV above the valence band maximum in LuAlO. Except for the oxygen vacancies which have a deep level inside the band gap, all other radiation-induced defects in LuAlO have shallow defect states or are outside the band gap, that is, relatively far away from either the 5d or the 4f Ce levels. Finally, we examine the role of Ga doping at the Al site and found that LuGaO has a band gap that is more than 2 eV smaller than that of LuAlO. Specifically, the lowered conduction band edge envelopes the defect gap states, eliminating their potential impact on scintillation performance and providing direct theoretical evidence for how band-edge engineering could be applied to rare-earth-doped perovskite scintillators.