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- All Subjects: Applied physics
- Creators: Holman, Zachary
- Resource Type: Text
Description
Interconnection methods for IBC photovoltaic (PV) module integration have widely been explored yet a concrete and cost-effective solution has yet to be found. Traditional methods of tabbing and stringing which are still being used today impart increased stress on the cells, not to mention the high temperatures induced during the soldering process as well. In this work and effective and economical interconnection method is demonstrated, by laser welding an embossed aluminum (Al) electrode layer to screen-printed silver (Ag) on the solar cell. Contact resistivity below 1mΩ.cm2 is measured with the proposed design. Cross-sectional analysis of interfaces is conducted via Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDXS) methods. Typical laser weld phenomenon observed involves Al ejection at the entrance of the weld, followed by Al and Ag fusing together mid-way through the weld spot, as revealed by cross-sectional depth analysis. The effects of voltage and lamp intensity are also tested on the welding process. With the range of voltages tested, 240V seems to show the least process variability and the most uniform contact between Al and Ag layers, upon using an Ethylene-Vinyl Acetate (EVA) encapsulant. Two lamp intensities were also explored with a Polyolefin (POE) encapsulant with Al and Ag layers seen welded together as well. Smaller effect sizes at lamp 2 intensity showed better contact. A process variability analysis was conducted to understand the effects of the two different lamps on welds being formed. Lamp 2 showed a bi-modal size distribution with a higher peak intensity, with more pulses coupling into the sample, as compared to lamp 1.
ContributorsSukumar Mony, Sujyot (Author) / Holman, Zachary (Thesis advisor) / Alford, Terry (Committee member) / Yu, Zhengshan (Committee member) / Arizona State University (Publisher)
Created2019
Description
In this dissertation, far UV spectroscopy is applied to investigate the optical properties of dielectric thin films grown by atomic layer deposition. The far UV (120 – 200 nm) reflectance for several dielectric oxides and fluorides, including AlF3, Al2O3, Ga2O3, HfO2, and SiO2, was measured at variable angles and thicknesses. Multiple optical calculation methods were developed for the accurate determination of the optical constants from the reflectance. The deduced optical constants were used for optical designs, such as high-reflectivity coatings, and Fabry-Perot bandpass interference filters. Three filters were designed for use at 157 nm, 212 nm, and 248 nm wavelengths, based on multilayer structures consisting of SiO2, Al2O3, HfO2, and AlF3. A thorough error analysis was made to quantify the non-idealities of the optical performance for the designed filters. Far UV spectroscopy was also applied to analyze material mixtures, such as AlF3/Al and h-BN/c-BN mixtures. Using far UV spectroscopy, different phases in the composite can be distinguished, and the volume concentration of each constituent can be determined. A middle UV reflective coating based on A2O3 and AlF3 was fabricated and characterized. The reflective coating has a smooth surface (?? < 1 nm), and a peak reflectance of 25 – 30 % at a wavelength of 196 nm. The peak reflectance deviated from the design, and an analysis of the AlF3 layer prepared by plasma-enhanced atomic layer deposition (PEALD) indicated the presence of Al-rich clusters, which were associated with the UV absorption. Complementary techniques, such as spectroscopic ellipsometry, and X-ray photoelectron spectroscopy, were used to verify the results from far UV spectroscopy. In conclusion, this Dissertation demonstrated the use of in-situ far UV spectroscopy to investigate the optical properties of thin films at short wavelengths. This work extends the application of far UV spectroscopy to ultrawide bandgap semiconductors and insulators. This work supports a path forward for far UV optical filters and devices. Various errors have been discussed with solutions proposed for future research of methods and materials for UV optics.
ContributorsHuang, Zhiyu (Author) / Nemanich, Robert (Thesis advisor) / Ponce, Fernando (Committee member) / Menéndez, Jose (Committee member) / Holman, Zachary (Committee member) / Arizona State University (Publisher)
Created2021