The effect of substitutional doping of Yb2+on structural, electronic, and optical properties of CsCa X3(X: Cl, Br, I) phosphors: a first-principles study

Rashid Khan; Kaleem Ur Rahman; Qingmin Zhang; Altaf Ur Rahman; Sikander Azam; Alaa Dahshan

doi:10.1088/1361-648X/ac3583

The effect of substitutional doping of Yb²⁺on structural, electronic, and optical properties of CsCa X₃(X: Cl, Br, I) phosphors: a first-principles study

J Phys Condens Matter. 2021 Nov 18;34(6). doi: 10.1088/1361-648X/ac3583.

Authors

Rashid Khan¹, Kaleem Ur Rahman², Qingmin Zhang¹, Altaf Ur Rahman³, Sikander Azam⁴, Alaa Dahshan^{5

6}

Affiliations

¹ School of Energy and Power Engineering, Xi'an Jiaotong University (XJTU), 28 Xianning W.Rd., Xi'an 710049, People's Republic of China.
² Department of Physics, Quaid-i-Azam University, Islamabad, Pakistan.
³ Department of Physics, Riphah International University, Lahore, Pakistan.
⁴ Department of Physics, Riphah International University, Islamabad, Pakistan.
⁵ Department of Physics, Faculty of Science, King Khalid University, PO Box 9004, Abha, Saudi Arabia.
⁶ Department of Physics, Faculty of Science, Port Said University, Port Said, Egypt.

PMID: 34727528
DOI: 10.1088/1361-648X/ac3583

Abstract

Using first-principles calculations, the effects of Yb²⁺substitutional doping on structural, electronic, and optical properties of a series of perovskite compounds CsCaX₃(X: 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 CsCaX₃(X: 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 CsCaX₃(X: Cl, Br, I) are 3.7 eV (GGA) and 4.5 eV (HSE) for CsCaI₃, 4.5 eV (GGA) and 5.3 eV (HSE) for CsCaBr₃, and 5.4 eV (GGA) and 6.4 eV (HSE) for CsCaCl₃. According to formation energies, the Yb²⁺doped at the Ca-site is thermodynamically more stable as compared to all possible atomic sites. The electronic band structures show that the Yb²⁺doping induces defective states within the bandgaps of pristine CsCaX₃(X: Cl, Br, I). As a result, the Yb²⁺doped CsCaX₃(X: Cl, Br, I) become the direct bandgap semiconductors. The defective states above the valence band maximum are produced due to thef-orbital of the Yb atom. The impurity states near the conduction band minimum are induced due to the major contribution ofd-orbital of the Yb atom and the minor contribution ofs-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 Yb²⁺doped CsCaX₃(X: 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 Yb²⁺doped CsCaX₃(X: Cl, Br, I) are appealing candidates for optoelectronic devices.

Keywords: DFT; electronic structure; inorganic phosphor materials; optical properties; perovskite.