期刊
ACS NANO
卷 8, 期 6, 页码 5863-5872出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn500897c
关键词
lead sulfide; ligands; quantum dots; nanocrystals; ultraviolet photoelectron spectroscopy; density functional theory; solar cells; photovoltaics
类别
资金
- Fannie and John Hertz Foundation
- National Science Foundation
- Samsung Scholarship Foundation
- Samsung Advanced Institute of Technology
The electronic properties of colloidal quantum dots (QDs) are critically dependent on both QD size and surface chemistry. Modification of quantum confinement provides control of the QD bandgap, while ligand-induced surface dipoles present a hitherto underutilized means of control over the absolute energy levels of QDs within electronic devices. Here, we show that the energy levels of lead sulfide QDs, measured by ultraviolet photoelectron spectroscopy, shift by up to 0.9 eV between different chemical ligand treatments. The directions of these energy shifts match the results of atomistic density functional theory simulations and scale with the ligand dipole moment. Trends in the performance of photovoltaic devices employing ligand-modified QD films are consistent with the measured energy level shifts. These results identify surface-chemistry-mediated energy level shifts as a means of predictably controlling the electronic properties of colloidal QD films and as a versatile adjustable parameter in the performance optimization of QD optoelectronic devices.
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