INCREASING SOLAR ENERGY CONVERSION EFFICIENCY IN HYDROGENATED AMORPHOUS SILICON PHOTOVOLTAIC DEVICES WITH PLASMONIC PERFECT META – ABSORBERS
Date of Award
Open Access Dissertation
Doctor of Philosophy in Materials Science and Engineering (PhD)
Administrative Home Department
Department of Materials Science and Engineering
Committee Member 1
Durdu O Guney
Committee Member 2
Paul L Bergstrom
Committee Member 3
Solar photovoltaic (PV) devices are an established, technically-viable and sustainable solution to society’s energy needs, however, in order to reach mass deployment at the terawatt scale, further decreases in the levelized cost of electricity from solar are needed. This can be accomplished with thin-film PV technologies by increasing the conversion efficiency using sophisticated light management methods. This ensures absorption of the entire solar spectrum, while reducing semiconductor absorber layer thicknesses, which reduces deposition time, material use, embodied energy and greenhouse gas emissions, and economic costs. Recent advances in optics, particularly in plasmonics and nanophotonics provide new theoretical methods to improve the optical enhancement in thin-film PV. The project involved designing and fabricating a plasmonic perfect meta-absorber integrated with hydrogenated amorphous silicon (a-Si:H) solar PV device to exhibit broadband, polarization-independent absorption and wide angle response simultaneously in the solar spectrum.
First, recent advances in the use of plasmonic nanostructures forming metamaterials to improve absorption of light in thin-film solar PV devices is reviewed. Both theoretical and experimental work on multiple nanoscale geometries of plasmonic absorbers and PV materials shows that metallic nanostructures have a strong interaction with light, which enables unprecedented control over the propagation and the trapping of light in the absorber layer of thin-film PV device. Based on this, the geometry with the best potential for the proposed device is identified and used for device modelling and, finally the plasmonic enhanced n-i-p a-Si:H solar cell with top surface silver (Ag) metallic structure is proposed. In order for the plasmonic enhanced PV device to be commercialized the means of nanoparticle deposition must also be economical and scalable. In addition, the method to fabricate silver nanoparticles (AgNPs) must be at lower temperatures than those used in the fabrication process for a a-Si:H PV device (less than 180 0C). The results indicate the potential of multi-disperse self-assemble nanoparticles (SANPs) to achieve broadband resonant response for a-Si:H PV devices. Finally a plasmonic enhanced a-Si:H PV using multi-disperse SANPs is realized when AgNPs are integrated to the commercially fabricated nip-a-Si:H PV devices. The devices are characterized for both quantum efficiency and light I–V to evaluate the cell parameters (Jsc, Voc, FF and η). Real–time spectroscopic ellipsometry (RTSE) data is used to model the device performance and the theoretical parameters are compared with the experimental data. Conclusions are drawn and recommendations and future work is suggested.
Gwamuri, Jephias, "INCREASING SOLAR ENERGY CONVERSION EFFICIENCY IN HYDROGENATED AMORPHOUS SILICON PHOTOVOLTAIC DEVICES WITH PLASMONIC PERFECT META – ABSORBERS", Open Access Dissertation, Michigan Technological University, 2016.