Ab initio study of the linear and nonlinear optical properties of hexagonal CdSe

Abstract

We present an ab initio theoretical study of the electronic, linear and nonlinear optical properties of CdSe using a pseudopotential plane-wave method. Since local density approximation (LDA) underestimates its band gap, we used the GW approximation method to calculate its quasiparticle band structure and obtain a band gap 1.67 eV in agreement with experimental value. The GW corrected gap was used as scissor shift to calculate the linear and nonlinear optical properties. Our calculations show that the optical absorption edge is located around 1.7 eV. The intraband and interband contributions to the imaginary part of second-order nonlinear optical susceptibility ߯ ଷଷଷ (ଶ) (2߱, ߱, ߱) are presented over a broad energy range. The calculated result for ቚ߯ ଷଷଷ (ଶ) (0)ቚ (at zero frequency limitation) is 74 pm/V, which is close to the experimental value 72pm/V.

Electro-optic Response in Germanium Halide Perovskites

“…The use of scissors corrections is necessary due to the problem of bandgap underestimation in DFT and the consequent overestimation of the dielectric properties. 21,30,31 The corrections act as rigid shifts to the conduction bands in order to curtail bandgap estimation and have been widely used in calculations of linear and nonlinear optical properties of many materials. 21,30−46 As empirical adjustments, these corrections introduce a degree of uncertainty to the calculations; however, as we show below, these corrections are validated by the strong agreement between the scissors-corrected and experimental SHG characteristics.…”

“…This activity distorts the perovskite unit cell, causing it to lose its inversion symmetry. The germanium halide perovskites are drawing increased interest as lead-free alternatives for photovoltaic application − and have also previously been reported to exhibit impressive second-harmonic generation (SHG), − a phenomenon intimately linked with LEO. Motivated by this fact, combined with their transparency over the infrared communications wavelengths ,, and evidence for growth of crystals from solution, ,,,,, we investigate herein the electro-optic and nonlinear optical behavior for germanium halide perovskites using density functional theory calculations.…”