Microconcentrators for Space Photovoltaics and Sputtered Nanoporous SiO2 Antireflection Coatings
- Ruud, Christian John
- [University Park, Pennsylvania] : Pennsylvania State University, 2022.
- Physical Description:
- 1 electronic document
- Additional Creators:
- Mohney, S. E.
- etda.libraries.psu.edu , Connect to this object online.
- Restrictions on Access:
- Open Access.
- This work explores a new microcell concentrating photovoltaic paradigm for space photovoltaics and develops a method to produce nanoporous SiO2 thin films for antireflection coatings. Optical concentration can improve the efficiency and reduce the cost of photovoltaic power, but has traditionally been too bulky, massive, and unreliable for use in space. Scaling the solar cell down to the microscale reduces the dimensions of the concentrator optics enabling ultra-compact, low-mass, and monolithic microcell concentrating photovoltaics ([mu]CPV) for space. Two [mu]CPV systems are introduced in this work. Design of the first begins with outlining the design principles and the derivation of the basic bounds on the compactness as a function of geometric concentration ratio and angular acceptance. A comparison among existing concentrator designs finds the simple reflective parabolic concentrator provides the best combination of specific power, angular acceptance, and overall fabrication simplicity for space [mu]CPV. The optical, electrical, and thermal performance of this architecture is simulated in detail and validated experimentally by a [mu]CPV built with transfer-printed microscale solar cells and molded microconcentrator optics. Finally, a discussion on the fundamental and practical limits on [mu]CPV is presented. The second space [mu]CPV system uses a new optical concentrator tailored specifically for the demands of space. The ultra-compact design is derived geometrically using the tailored-edge ray principle and is shown to approach the fundamental limit of maximum concentration in two dimensions. Simulations find the compactness, angular tolerance, and specific power of the new concentrator compares favorably against our first parabolic reflector system. The design is demonstrated with a single cell proof-of-concept system constructed with a diamond turned glass optic. The tailored-edge ray concentrator operates at over four times higher concentration than our first system and improves the power conversion efficiency. Together the two designs lay the groundwork for ultra-compact space microconcentrators that could serve as a higher efficiency, lower cost alternative to conventional space photovoltaics. The second major focus of this dissertation is on the development of a magnetron sputtering method to produce graded refractive index antireflection (AR) coatings. Graded index coatings offer wide-angle broadband antireflection, but lack a scalable fabrication process that would enable them to be used more widely in applications such as architecture and solar energy conversion. The method introduced here uses a sacrificial porogen approach to produce multilayer nanoporous SiO2 films with refractive index values tuneable from near SiO2 down to near air. The technique is demonstrated with a step-graded bilayer coating that provides broadband, wide-angle performance. The chemical and morphological structure is investigated to provide insights to the fabrication process. Physical testing finds these films have good adhesion strength, whereas damp heat and ultraviolet illumination testing show promising environmental durability. These results open up a path to produce ultrahigh performance AR coatings over large areas using industrial-scale magnetron sputtering systems. The potential benefit is discussed in context of AR coatings for terrestrial solar cells and simulations find the sputtered coatings increase the annual yield of a photovoltaic panel.
- Other Subject(s):
- Dissertation Note:
- Ph.D. Pennsylvania State University 2022.
- Technical Details:
- The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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