Effect of cation doping on tuning intrinsic defects in LuI3

LuI₃:Ce is considered to be a candidate scintillator in radiation detectors for high energy physics and nuclear medicine due to high light yield. However, slow decay induced by energy transfer from self-trapped excitons on intrinsic defects to Ce limits the time resolution of detectors. The effect of Li, Cu, Mg, and Zn doping on tuning the intrinsic defects in LuI₃ are investigated using first-principles calculations. The thermodynamic levels introduced by the Lu interstitials and the I vacancies turn out to match emission energies of the self-trapped excitons. The cation interstitials enhance the formation energies of the Lu interstitials and I vacancies because of charge balance. Importantly, Mg doping is demonstrated to effectively suppress the Lu interstitials and the I vacancies in LuI₃