Engineered Type-II Heterostructures For High Efficiency Solar Cell Applications
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The third-generation solar cell technologies are aiming to achieve substantially higher efficiency over the Shockley-Queisser limit of a single junction solar cell while maintaining low fabrication cost per area in order to become cost competitive with coal fuel. The demanding of a breakthrough in efficiency leads the research to the development of photovoltaic devices with a new concept of fundamental operation other than the structure of single junction solar cells and to the employment of various materials and nanostructures to the devices.
The purpose of the projects in this dissertation to present nanostructures with type-II heterointerface that can provide additional possibilities to certain types of third generation solar cells for achieving an efficiency close to the theoretical maximum limit.
First, the electronic structure and optical properties of type-II GaAsBi/GaAsN superlattices with effective lattice match to GaAs are studied based on the 8-band k.p method and Self-consistent Schrodinger-Poisson equations showing a new material system in a spectral range of high importance for the multi-junction solar cells.
Second, the electronic structure, optical properties, and thermal carrier capture and escape mechanisms of the type-II GaSb/GaAs self-assembled quantum dots (QDs) are studied theoretically and experimentally to examine the advantages of the heterostructure for the intermediate band solar cells (IBSCs). GaSb/GaAs QD-IBSCs are fabricated to present the utilization of the type-II QDs on the solar energy conversion in the IBSCs.