Abstract:
Theoretical investigation of solar cell materials facilitates strong precision of structure, and determination of electronic properties. Within this thesis, the electronic properties of cubic metal-halide ABX3 perovskites (A=Cs,MA B=Pb,Sn X=Cl,Br,I) are modelled in order to elucidate phase-dependent electronic properties and systematic accuracy. These materials are of interest for solar cell applications, and are shown to be heavily dependent upon the extent of both internal and external pressure upon the perovskite structure. These results highlight possibilities for band-tuning in metal-halide perovskites, thereby providing insight on how to optimize photovoltaic materials based on structure and composition. The photovoltaic materials CsPbBr3 and MAPbBr3 exhibit similar electronic properties. [1, 2] In this thesis, the phase-and-structure-dependent electronic properties of these two systems are calculated and compared. Slight distortion of the Br6 framework is responsible for substantial changes in electronic properties. Investigation reveals MAPbBr3 to be more sensitive to distortion of the lead-halide framework than CsPbBr3. Thallium lead halides were modelled in order to compare to experimental novel thallium lead chloride bromide and iodide nanocrystals and nanowires. These results supported the existence of halide and mixed halide thallium compounds. Finally, gallium, another group 13 element, was investigated as a 2-dimensional nanomaterial. The robust metallicity of this material was demonstrated by density functional calculations, including simulation of lattice strain.
