Investigation of structural, electronic, and optical properties of Er-doped KNN system based on first-principles calculations

Abstract

Potassium sodium niobate (KNN)-based ceramics exhibit electrical (such as ferroelectric) and photoluminescence (PL) properties and have great application potential in the field of multifunctional optoelectronics. To promote its development in the field of optoelectronics, researchers have been making efforts to improve its photoelectric performance, but mainly through experimental approach with little fundamental theoretical calculations. In this paper, the structural, electronic, and optical properties of (K_0.5Na_0.5)NbO₃, K_0.375Na_0.5Er_0.125NbO₃ and K_0.5Na_0.375Er_0.125NbO₃ material were simulated based on first-principles calculations. The calculation of formation energy reveals that Er is more inclined to replace Na than A-site K. The introduction of Er leads to a decrease in the lattice constant of the structure, and the oxygen octahedron relaxes inward, which is beneficial to the enhancement of ferroelectricity. The orbital hybridization of Er-4f and O-2p leads to a narrower band gap and an increase in absorbance and conductivity. The A-site substitution of Er produces a non-uniform chemical bond environment locally, which is beneficial to the improvement of PL performance. These results provide theoretical insights for doping mechanism of the KNN-Er system and show its potential in the field of optoelectronic applications.