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 Ce3+-doped LuAlO3 as a model material system, using density functional theory (DFT)-based DFT + U and hybrid Heyd-Scuseria-Ernzerhof (HSE) calculations. From spin-polarized hybrid HSE calculations, the Ce3+ activator ground-state 4f position is determined to be 2.81 eV above the valence band maximum in LuAlO3. Except for the oxygen vacancies which have a deep level inside the band gap, all other radiation-induced defects in LuAlO3 have shallow defect states or are outside the band gap, that is, relatively far away from either the 5d1 or the 4f Ce3+ levels. Finally, we examine the role of Ga doping at the Al site and found that LuGaO3 has a band gap that is more than 2 eV smaller than that of LuAlO3. 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.