Electron transfer in hydrogenated nanocrystalline silicon observed by time-resolved terahertz spectroscopy

被引:19
作者
Bergren, Matthew R. [1 ,4 ]
Simonds, Brian J. [1 ]
Yan, Baojie [2 ]
Yue, Guozhen [2 ]
Ahrenkiel, Richard [3 ,4 ]
Furtak, Thomas E. [1 ]
Collins, Reuben T. [1 ]
Taylor, P. Craig [1 ]
Beard, Matthew C. [4 ]
机构
[1] Colorado Sch Mines, Dept Phys, Golden, CO 80401 USA
[2] United Solar Ovon, Auburn Hills, MI 48326 USA
[3] Colorado Sch Mines, Met & Mat Engn Dept, Golden, CO 80401 USA
[4] Natl Renewable Energy Lab, Golden, CO 80401 USA
关键词
DEFECT; SI;
D O I
10.1103/PhysRevB.87.081301
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
We report on the ultrafast carrier dynamics in hydrogenated nanocrystalline silicon (nc-Si: H) using time-resolved terahertz spectroscopy. Photoexcitation at 407 nm primarily produces charge carriers in the a-Si phase, but they undergo a rapid electron transfer to the c-Si phase prior to complete thermalization into the band-tail states of a-Si. We studied the carrier dynamics on a range of nc-Si: H samples with varying crystalline volume fractions (X-c) and mapped out the carrier dynamics with sub-ps resolution. Our measurements are consistent with a model in which electrons are first trapped at interface states at the a-Si-c-Si boundary prior to being thermally emitted into the c-Si phase. Wavelength and temperature dependent measurements are consistent with our model. The phenomena observed here have implications toward solar cell structures that utilize an amorphous material as an absorber layer, previously thought to have a mobility value too low to attain effective charge transport in a device. DOI: 10.1103/PhysRevB.87.081301
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页数:5
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