Investigation of the structural, electronic, and optical properties of Mn-doped CsPbCl: theory and experiment.

Wide energy gap inorganic halide perovskites have become emerging candidates for potential applications in modern optoelectronics devices. However, to date, these semiconducting compounds have not been explored theoretically to a significant extent. Herein, we performed computations to explain the structural, electronic and optical behaviour of inorganic CsPbCl and Mn-doped CsPbCl nanocrystals (NCs). We also synthesized these NCs and further validated our experimental results with density functional theory (DFT) calculations. The results provide insight into the effect of Mn doping on the important properties of CsPbCl NCs such as their lattice parameter, electronic band structure, density of states, dielectric constant, absorption coefficient and refractive index. After geometry optimization using the Limited-memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) algorithm, a reduction in the lattice parameter from 5.605 Å to 5.574 Å was observed after doping Mn in the CsPbCl NCs, which is in good agreement with the calculated results from the X-ray diffraction (XRD) pattern (5.610 Å to 5.580 Å) and high-resolution transmission electron microscopy (HRTEM) images (5.603 Å to 5.575 Å). The incorporation of Mn in CsPbCl was observed in the electronic band structure in the form of additional states present in the energy gap and an increment in the band gap of the CsPbCl NCs. This result is consistent with the photoluminescence (PL) plot, which showed dual color emission in the case of the Mn-doped CsPbCl, which is attributed to the Mn d-band to d-band transition. The partial density of states (PDOS) of the Mn-doped CsPbCl NCs clearly indicates the contribution of the Mn 3d orbitals to the upper valence band and conduction band together with the contribution of the Pb 6p and Cl 3p orbitals. Moreover, a blue-shift phenomenon was observed from the dielectric constant and absorption coefficient spectra, which is due to the incorporation of Mn in CsPbCl. Also, a significant peak was observed in the absorption coefficient and dielectric constant spectra around 2.08 eV, which is in good agreement with the PL plot. This DFT study with experimental observation provides a way to investigate this type of compound and to tailor its interesting characteristics through doping.