Matching Items (2)
Description
GaAs-based solar cells have attracted much interest because of their high conversion efficiencies of ~28% under one sun illumination. The main carrier recombination mechanisms in the GaAs-based solar cells are surface recombination, radiative recombination and non-radiative recombination. Photon recycling reduces the effect of radiative recombination and is an approach to obtain the device performance described by detailed balance theory. The photon recycling model has been developed and was applied to investigate the loss mechanisms in the state-of-the-art GaAs-based solar cell structures using PC1D software. A standard fabrication process of the GaAs-based solar cells is as follows: wafer preparation, individual cell isolation by mesa, n- and p-type metallization, rapid thermal annealing (RTA), cap layer etching, and anti-reflection coating (ARC). The growth rate for GaAs-based materials is one of critical factors to determine the cost for the growth of GaAs-based solar cells. The cost for fabricating GaAs-based solar cells can be reduced if the growth rate is increased without degrading the crystalline quality. The solar cell wafers grown at different growth rates of 14 μm/hour and 55 μm/hour were discussed in this work. The structural properties of the wafers were characterized by X-ray diffraction (XRD) to identify the crystalline quality, and then the as-grown wafers were fabricated into solar cell devices under the same process conditions. The optical and electrical properties such as surface reflection, external quantum efficiency (EQE), dark I-V, Suns-Voc, and illuminated I-V under one sun using a solar simulator were measured to compare the performances of the solar cells with different growth rates. Some simulations in PC1D have been demonstrated to investigate the reasons of the different device performances between fast growth and slow growth structures. A further analysis of the minority carrier lifetime is needed to investigate into the difference in device performances.
ContributorsZhang, Chaomin (Author) / Honsberg, Christiana (Thesis advisor) / Goodnick, Stephen (Committee member) / Faleev, Nikolai (Committee member) / Arizona State University (Publisher)
Created2014
Description
This project details the learning of processes in nanofabrication and sensor detection fields. We sought to apply this knowledge to develop a processing procedure to fabricate sensors used to detect high energy protons. We seek to create such a sensor to be applied to aid Mayo Clinic’s Proton Beam Therapy center for cancer treatment through providing beam detection measurements. Developed plans would allow for proton beam detectors to be able to measure beam intensity and direction which would allow for more accurate beam treatments. Current detectors require much calibration and solid state detectors can’t withstand the high-energy exposure of the proton beam for long durations. By fabricating pixelated diamond sensors we expect to produce sensitive beam readings, while extending detector length time due to diamonds durable crystalline lattice. We report processing procedures for simple 2-3 contact detectors as well as more complex multi-contact pixelated sensors used for spatial resolution of the beam. Testing of simple sensors is additionally reported with successful radioactive source detection.
ContributorsVan Engelhoven, Trevor James (Author) / Nemanich, Robert (Thesis director) / Zaniewski, Anna (Committee member) / Department of Physics (Contributor, Contributor) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12