Tailoring the electronic and optical properties of CsAuCl₃ via rare-earth doping: A GGA + U + SOC DFT study for phosphor-converted LEDs and advanced optoelectronic applications

Abstract

This study presents aninclusive first-principles investigation of pristine CsAuCl₃ and its rare-earth doped variants (Eu, Tb) using density functional theory (DFT) with the Wien2k implementation of the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method. The calculations incorporate Generalized Gradient Approximation (GGA) with Hubbard U correction and Spin-Orbit Coupling (SOC) to accurately model the strongly correlated f-electrons of the rare-earth dopants. The electronic structure calculations reveal that pristine CsAuCl₃ exhibits semiconducting behavior with an indirect bandgap of 0.672 eV. Upon doping, significant modifications occur: Eu-doped CsAuCl₃ maintains semiconducting character but with a substantially reduced bandgap of 0.034 eV, while Tb-doping induces a transition to metallic behavior. Density of States (DOS) analysis demonstrates pronounced spin polarization in Eu-doped samples, suggesting potential magnetic properties arising from the interaction between Eu 4f states and the host electronic structure. Formation energy calculations confirm the thermodynamic stability of both pristine and doped configurations. Optical property calculations show that rare-earth doping significantly enhances the material's optical response. Doping of Eu and Tb enhances the absorption in infrared, visible, and ultraviolet spectral regions. Notably, Eu-doped CsAuCl₃ exhibits a dramatic enhancement in its static dielectric constant (ε₁(0) = 26.41) compared to the pristine material (ε₁(0) = 2.26). This systematic investigation demonstrates the potential of rare-earth doping for tailoring the electronic and optical properties of CsAuCl₃, suggesting promising applications in phosphor-converted LEDs, photovoltaics, and advanced optoelectronic devices. The results provide fundamental insights into the quantum mechanical mechanisms underlying the observed property modifications while establishing a theoretical framework for future materials engineering in this class of compounds.