Theoretical Investigation of the Properties of the Hot Carrier Solar Cell and a Candidate Material

Abstract

The hot carrier solar cell (HCSC) is a novel concept of an advanced solar cell whose efficiency has the potential to exceed the Shockley-Queisser efficiency limit. The HCSC requires an absorber with slowed carrier relaxation time, energy selective contacts (ESC) and a good compatibility between these two components. The aim of the study presented in this thesis is to theoretically investigate a candidate material for the hot carrier solar cell (HCSC) from both the device level and the atomic level. The device level theoretical modelling of the HCSC using the modified relaxation time approximation (RTA) model with parameterization from the experimental data of InAlAs/ InGaAs MQW. The primary goal of this simulation is to find the optimized ESC setup which includes both the carrier extraction energy level and energy window width. The atomic level theoretical modelling of the Lead Selenide (PbSe) material and its corresponding quantum dot facades have been illustrated in searching for a suitable material for the HCSC. The first goal of the study is to understand the nature of the PbSe QD passivation from the inorganic ligand treatment and to investigate the relationship between the corresponding ligand density and the passivation quality. The PbSe (001), (110) and (111) surfaces with chlorine, bromine and iodine ligands are investigated with the density functional theory (DFT) calculations with the linear combination of atomic orbital (LCAO) basis and the Perdew–Burke–Ernzerhof (PBE) exchange correlation functional implemented. The second aspect is to quantitatively identify the carrier transport between the PbSe QD facades with various types of halide ligand and ligand coverage levels. In addition, the impact of surface defects and passivation on the carrier transport between surfaces is analysed with quantitative results. The quantum conductance profiles are calculated with the non-equilibrium Greens functions (NEGF) where the DFT calculations are also employed for the feed-in Hamiltonian matrices.