Electronic properties of perovskite nanocrystals

[M. M. Jocić]

214 стр.

Biografija i bibliografija autora: str. [215]. Bibliografija: str. 203-214.

Electronic properties of nanostructures

Halide perovskite materials have been investigated in detail experimentally over the years due to their exceptional optoelectronic properties. However, many questions remained open which call for appropriate theoretical research. Theoretical investigations were mainly focused on crystalline perovskite materials and were based on the application of ab initio methods for calculation of electronic structure of materials. These methods cannot be applied in practice to nanocrystals which contain a large number of atoms and hence the calculation cannot be performed in reasonable timeframe. The methods that enable investigation of electronic states in perovskite nanocrystals are developed in this thesis. The first subject of this work is the development of method that uses the result of ab initio calculation of crystalline material in bulk phase to construct the symmetry-adapted Hamiltonian. The parameters from such Hamiltonian can be used to construct a Hamiltonian in the envelope function representation, which can be applied to nanocrystals. Second, the electronic structure of halide perovskite materials is investigated in detail, taking into account all relevant effects. This includes the electron exchange and correlation effects, as well as temperature effects that stem from electron-phonon interaction. The exchange and correlation is included using hybrid PBE0 functional modified to meet the Koopmans' condition within DFT framework. The temperature effects are obtained using modified Allen-Heine-Cardona method: transition matrix elements due to phononic perturbation are obtained using density functional perturbation theory, phonon frequencies are obtained from selfconsistent phonon method that takes anhаrmonic effects into account, while broadening and renormalization of the bands is treated simultaneously using self-consistent procedure based on Migdal approximation. Finally, the temperature dependent electronic states in perovskite nanocrystals are computed for quantum wells, wires and dots of various sizes.

elektronska svojstva, elektronska struktura, halidni perovskiti, nanokristali, ab initio, teorija funkcionala gustine (DFT), k·p metod, elektron-fonon interakcija, simetrijska adaptacija, grupe simetrija, kvantna jama, kvantna žica, kvantna tačka.

electronic properties, electronic structure, halide perovskites, nanocrystals, ab initio, density functional theory (DFT), k·p method, electron-phonon interaction, symmetry adaptation, symmetry groups, quantum well, quantum wire, quantum dot.

621.38:621.383.51(043.3)

P 260; P 265

Tekst