Efeito da adição dos dopantes Co e N nas estruturas eletrônicas de perovskitas à base de (K, Na)NbO3: um estudo computacional via Teoria do Funcional da Densidade

Abstract

The present work addresses a theoretical/computational study of the electronic properties of KNbO3 and NaNbO3 perovskites. Using the Density Functional The ory (DFT), the effect of doping and co-doping with cobalt and nitrogen is evaluated as a way of maximizing the photovoltaic effect and, consequently, enabling its use in perovskites solar cells (CSP). As DFT demonstrably underestimates certain prop erties such as band gap, the use of the pseudo-hybrid approximation of the ACBN0 functional is proposed and evaluated, which incorporates the Hubbard correction as a natural function of electron density and chemical environment. In this context, density of states (DOS) and band structure calculations, charge analysis, geometry, effective masses of charge carriers and formation and binding energies of defects (doping) were established. The strategy of adding barium and strontium is also examined as a way of stabilizing the structure and charges. The methodology proved to be efficient, since, among other issues, it showed reductions and adjustment band gap through the ap pearance of intermediate states generated by dopants, spin polarization that highlights magnetic effects (doping with cobalt), increase in the effective masses of charge car riers in the valence band (BV), which decrease mobility, but also minimize the charge recombination rate and formation and binding energies, which showed that codoping produces more stable structures than individual dopings. As a result, the photovoltaic potential of the studied perovskites and their application in CSP are confirmed.