Single-Crystalline InGaAs/InP Dense Micro-Pillar Forest on Poly-Silicon Substrates for Low-Cost High-Efficiency Solar Cells
The ultimate goal of this project is to develop a photovoltaic system high conversion efficiency (>20%) using high quality III-V compound-based three-dimensional micro-structures on silicon and poly-silicon. Such a PV-system could be of very low cost due to minimum usages of III-V materials. This project will address the barriers that currently hamper the performance of solar cells based on three-dimensional micro-structures. To accomplish this goal the project is divided into 4 tasks, each dealing with a different aspect of the project: materials quality, micropillar growth control, light management, and pillar based solar cells. Materials Quality: the internal quantum efficiency (IQE) - by which is meant here the internal fluorescence yield - of the micro-pillars has to be increased. We aim at achieving an IQE of 45% by the end of the first year. By the end of the second year there will be a go-no-go milestone of 65% IQE. By the end of year 3 and 4 we aim to achieve 75% and 90% IQE, respectively. Micropillar growth control: dense forests of micropillars with high fill ratios need to be grown. Pillars within forests should show minimum variations in size. We aim at achieving fill ratios of 2%, 10%, >15%, >20% in years 1, 2, 3, and 4, respectively. Variations in dimension should be minimized by site-controlled growth of pillars. By the end of year 1 we will aim at achieving site-controlled growth with > 15% yield. By end of year 2 the variation of critical pillar dimensions should be less than 25%. Light management: high light absorption in the spectral range of the sun has been to be demonstrated for the micropillar forests. By the end of year 1 we will employ FDTD simulation techniques to demonstrate that pillar forests with fill ratios <20% can achieve 99% light absorption. By end of year 2 our original goal was to demonstrate >85% absorption. By end of year 3 > 90% absorption should be demonstrated. Pillar based solar cells: devices will be studied to explore ways to achieve high open-circuit voltages which will lead to high efficiency micropillar-based solar cells. We will start on single pillar devices and the findings in these studies should pave the way for devices based on forests/ arrays of pillars. By the end of the second year we aim to demonstrate a single pillar device with an open-circuit voltage of 0.7 V, as well as a pillar-forest based device with 8% conversion efficiency. By the end of year 3 these numbers should be improved to 0.9 V open-circuit voltage for single pillar devices and >15% efficiency for forest/array-based devices. We will aim to realize a device with 20% efficiency by the end of the project period.
- Research Organization:
- Univ. of California, Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- DOE Contract Number:
- EE0005316
- OSTI ID:
- 1178992
- Report Number(s):
- DOE-UC Berkeley-0005316-Q13
- Country of Publication:
- United States
- Language:
- English
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