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Hot Carrier Solar Cell {HC-SC) is one of the advanced photovoltaic technologies. The two main building blocks of a HC-SC are: the absorber, where electrons- holes pairs are photo generated by absorbing the incoming photons, and the energy selective contacts, which allow extraction of these carriers to the external circuit in a narrow range of energies. HC-SCs offer the possibility of operating at very high efficiencies (Limiting efficiency above 65% for un-concentrated light) with structure of reduced complexity. An ideal HC-SC operates at very high efficiency by absorbing wide range of photon energies and extracting the photo-generated carriers at elevated temperatures before they thermalize to the band-edge of the absorber material. The finding of suitable absorber material and its fabrication along with characterisation are the initial steps to implement the HC-SC with a better efficiency. Germanium Carbide {Gee) and Zirconium nitride (ZrN) have a large mass difference between their consecutive elements and exhibit a large phonon band gap sufficient to block the dominant carrier cooling mechanism by Klemens decay route. In this thesis, Gee and ZrN have been studied to investigate their suitability as absorbers for HC-SCs. These material have been fabricated using sputtering and characterised using an array of techniques such as X-ray photoelectron spectroscopy, transmission microscopy, X-ray diffraction, Raman spectroscopy, Atomic Force Microscopy and optical absorption spectroscopy to study structural, compositional and optical properties. Transient absorption spectroscopy was used to study the carrier dynamics. Nano-crystalline Gee has been fabricated which may be suitable for photovoltaic application. Germanium carbide with the record of 15.5 % Gee has been demonstrated. Growth of ZrN have been demonstrated in the range of process parameters. Epitaxial growth of ZrN on MgO substrate has been achieved with DC sputtering at 500°C. Carrier dynamics in ZRN film ha

This study aims to realize effective energy selective contacts (ESCs) for hot carrier solar cells (HCSCs) by using quantum well structures based on silicon or germanium wells. HCSCs require highly selective ESCs to extract optimal hot carriers only, in order to achieve high efficiency. ESCs rely on resonant tunnelling phenomena in ultrathin quantum well devices such as double-barrier resonant tunnelling diodes (DB RTD). To find suitable barrier materials for Si and Ge, an in-depth review is carried out to sort previous DBRTDs according to their materials and to compare their performance, by which Al2O3 is identified as the most potential barrier material. Two experimental approaches are carried out to construct DBRTDs with amorphous Al2O3 (a-Al2O3) and crystalline Al2O3 (c-Al2O3) barriers, respectively. For a-Al2O3 barriers, two types of wells, thermally annealed nanocrystalline Ge (nc-Ge) films and Si quantum dots (QDs) deposited by Langmuir-Blodgett (LB) method, are employed. For the c-Al2O3 barriers, sputtering and pulsed laser deposition (PLD) are used to grow hetero-epitaxial gamma-Al2O3 films on Si substrates. The DBRTD based on a-Al2O3/nc-Ge achieves room temperature resonant tunnelling with peak to valley ratio (PVCR) 2.43, full width at half maximum (FWHM) 0.05V, and peak current density (PCD) 2.1A/cm2, applicable for ESCs. High selection with a quality factor (PVCR 20.5/FWHM 0.012V) 1708/V has been achieved by the DBRTD of a-Al2O3/Si QD at room temperature, very promising for the ESC purpose. A 3nm strained layer of epitaxial gamma-Al2O3 is achieved by sputtering on Si (100) substrates, with ideal interfaces for RTD purpose. The novel e-beam annealed epitaxy of gamma-Al2O3 on Si (111) substrates is observed, with thick strained layers up to 14nm. PLD achieves 56nm thick relaxed hetero-epitaxial gamma-Al2O3 films on Si (111) substrates, potential for RTD and the epitaxy of III-V materials on Si. To integrate ESCs with HCSCs, calculations based on conservati

Photovoltaics is considered to be one of the best alternatives to fossil fuels to meet global energy demand. The improvement of solar cell efficiency beyond the Shockley-Queisser limit and towards the thermodynamic limit may be realized through “third generation photovoltaic” concepts. Two major strands of research in third generation photovoltaics are hot carrier solar cells and tandem solar cells. In the former, carriers are extracted before they cool down to the band edges, while the latter employs superlattices for more effective conversion of sunlight. High efficiencies in these cells are achieved by using materials engineered at the nanoscale.A hot carrier solar cell has two parts: a hot carrier absorber and a selective energy contact for energetically filtering electrons. Quantum dot double barrier structures are the most suitable candidates for making energy selective contacts. In this work, I have developed a 3 dimensional model using effective mass approximation and scatter matrix methods to study resonant tunnelling transport through energy selective contacts. The impacts of disorder in the position and size of the quantum dots on the conductivity of the structure are investigated. A novel design using alternating layered dielectrics is analysed using this model and found to have significant advantages over double barrier structures lacking this feature. The confined energy in quantum dots depends on their size and shape. Recent characterization techniques have shown that only a few dots in a self assembled layer represent an ordered array of spherically shaped dots. An efficient, self-consistent 3 dimensional, model for calculating energy confinement and wavefunctions in quantum dots of arbitrary shapes is developed using Multi Grid algorithms. Silicon quantum dots and their interaction in different dielectric materials are analysed for the best performance in tandem solar cells.Optically assisted I-V is carried out on structures with silicon q