| 项目编号: | 1438608
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| 项目名称: | Core-shell Upconverting Nanostructures (CSUNs) for Photovoltaics |
| 作者: | Mark Wistey
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| 承担单位: | University of Notre Dame
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| 批准年: | 2013
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| 开始日期: | 2014-09-01
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| 结束日期: | 2018-08-31
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| 资助金额: | USD365865
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| 资助来源: | US-NSF
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| 项目类别: | Standard Grant
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| 国家: | US
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| 语种: | 英语
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| 特色学科分类: | Engineering - Chemical, Bioengineering, Environmental, and Transport Systems
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| 英文关键词: | solar cell
; csun
; energy
; core-shell
; efficiency
; project
; upconversion
; solar spectrum
; process
; core-shell nanostructure
; core-shell upconverting nanostructure
; work
; electron
; new csun design
; step
|
| 英文摘要: | Principal Investigator: Mark Wistey
Number: 1438608
The sun represents the most abundant potential source of pollution-free energy on earth. Solar cells for producing electricity require materials that absorb the sun's energy and convert its photons to electrons, a process called photovoltaics. Current photovoltaic solar cells are not able to fully utilize all of the energy in the solar spectrum. This project seeks to sharply improve the efficiency of solar cells beyond 50%, and maintain this efficiency even when the spectrum changes due to morning light, evening light, and haze. A conventional solar cell is only efficient at generating electricity from a single color of light. This proposal seeks to capture more of the solar spectrum using upconversion, a process where several low-energy colors are absorbed in separate steps, producing high energy electrons as the output. Upconversion requires a process called energy ratcheting, with allows electrons to lift to a higher energy state. Typical upconversion materials such as germanium allow only one ratcheting step. The goal of this project is use core-shell materials ordered at the nanoscale to promote two ratcheting steps. These core-shell upconverting nanostructures (CSUNs) have strong potential to increase the efficiency of even the best existing solar cells. CSUNs would also deliver power more uniformly during overcast and dusk/dawn hours, which would provide more even production of power for distribution to the electrical grid. This project also includes educational and outreach science demonstrations to reach economically disadvantaged schools in the South Bend/Michiana area of Indiana to stimulate interest in STEM fields.
Technical Description
Current photovoltaic solar cells are not able to fully utilize all of the energy in the solar spectrum. Upconversion is a process to capture more of the solar spectrum where several low-energy colors are absorbed in separate steps, producing high energy electrons as the output. The overall goal of this project is to develop core-shell nanostructures for upconversion in photovoltaic solar cells to improve solar energy conversion efficiency. A major challenge in upconversion is the need for energy ratcheting, which allows for electrons to be lifted to successively higher energies without falling back down. Energy ratcheting is possible using a material such as germanium, which strongly absorbs light but does not re-emit it. The proposed research seeks to add a second energy ratcheting step using core-shell nanostructures within the solar cell. In this design, excited electrons can escape from the core directly into the host solar cell, but a shell barrier prevents them from falling back into the core. The proposed research will synthesize heterogeneous, interleaved growth of III-V (AlGaAs) and Group IV (Ge) semiconductors with no extended defects, and then fabricate a family of core-shell upconverting nanostructures (CSUNs) using germanium self-assembled quantum dots or islands embedded as individual cores within a wide bandgap AlAs or AlGaAs shell layer. The shell layer is embedded in a contiguous host of AlGaAs or GaAs with a slightly smaller bandgap. Ge is chosen as the core material because its excited carrier lifetimes of around one millisecond are long enough for absorption of a second photon. Within this context, the first objective in this work is to optimize growth of the Ge-AlAs-GaAs core-shell structure to maximize upconversion efficiency, and examine whether this system can exceed the efficiency of a conventional tandem cell. The second objective is to test whether self-assembled CSUNs are sufficient for high efficiency, by characterizing faceted growth, host mobility, and absorption strengths. The third objective is to use these experimental results to predictively model and identify optimal band structures and materials for new CSUN designs. The final objective is to combine CSUNs with advanced techniques such as plasmon resonant absorption, photon management, and bandpass absorption, and insert them in multi-junction cells and characterize efficiency. If successful, this work has the potential to significantly increase solar cell efficiency and preserve current matching in multi-junction cells. The physical principles developed in this work also have strong potential to enable the design and evaluation of a new generation of nanocomposite solar materials. This project also includes educational and outreach science demonstrations to reach economically disadvantaged schools in the South Bend/Michiana area to stimulate K12 student interest in STEM fields. |
| 资源类型: | 项目
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/95717
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| Appears in Collections: | 影响、适应和脆弱性
气候减缓与适应
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| Recommended Citation: | |
Mark Wistey. Core-shell Upconverting Nanostructures (CSUNs) for Photovoltaics. 2013-01-01.
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