The effect of substitutional doping of Ybon structural, electronic, and optical properties of CsCa(: Cl, Br, I) phosphors: a first-principles study.

Using first-principles calculations, the effects of Ybsubstitutional doping on structural, electronic, and optical properties of a series of perovskite compounds CsCa(: Cl, Br, I), have been investigated. We employed generalized gradient approximation (GGA) and HSE hybrid functional to study the electronic and optical properties. A series of pristine CsCa(: Cl, Br, I) is characterized as a non-magnetic insulator with indirect bandgap perovskite materials. These phosphor materials are suitable candidates for doping with lanthanide series elements to tune their electronic bandgaps according to our requirements because of their wide bandgaps. The calculated electronic bandgaps of CsCa(: Cl, Br, I) are 3.7 eV (GGA) and 4.5 eV (HSE) for CsCaI, 4.5 eV (GGA) and 5.3 eV (HSE) for CsCaBr, and 5.4 eV (GGA) and 6.4 eV (HSE) for CsCaCl. According to formation energies, the Ybdoped at the Ca-site is thermodynamically more stable as compared to all possible atomic sites. The electronic band structures show that the Ybdoping induces defective states within the bandgaps of pristine CsCa(: Cl, Br, I). As a result, the Ybdoped CsCa(: Cl, Br, I) become the direct bandgap semiconductors. The defective states above the valence band maximum are produced due to the-orbital of the Yb atom. The impurity states near the conduction band minimum are induced due to the major contribution of-orbital of the Yb atom and the minor contribution of-orbital of the Cs atom. The real and imaginary parts of the dielectric function, optical reflectivity, electron energy loss spectrum, extinction coefficient, and refractive index of pristine and Ybdoped CsCa(: Cl, Br, I) were studied. The optical dispersion results of dielectric susceptibility closely match their relevant electronic structure and align with previously reported theoretical and experimental data. We conclude that the Ybdoped CsCa(: Cl, Br, I) are appealing candidates for optoelectronic devices.