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Absolute Energy Level Positions in CdSe Nanostructures from Potential-Modulated Absorption Spectroscopy (EMAS)
Spittel, D. Poppe, J. Meerbach, C. Ziegler, C. Hickey, Stephen G. Eychmüller, A.
Spittel, D.
Poppe, J.
Meerbach, C.
Ziegler, C.
Hickey, Stephen G.
Eychmüller, A.
Publication Date
2018
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© 2018 ACS. This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano.
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Abstract
Semiconductor nanostructures like CdSe quantum dots and colloidal nanoplatelets
exhibit remarkable optical properties, making them interesting for applications in optoelectronics
and photocatalysis. For both areas of application a detailed understanding of
the electronic structure is essential to achieve highly efficient devices. The electronic
structure can be probed using the fact that optical properties of semiconductor nanoparticles
are found to be extremely sensitive to the presence of excess charges that can for
instance be generated by means of an electrochemical charge transfer via an electrode.
Here we present the use of potential modulated absorption spectroscopy (EMAS) as
a versatile spectroelectrochemical method to obtain absolute band edge positions of
CdSe nanostructures versus a well-defined reference electrode under ambient conditions.
In this the spectral properties of the nanoparticles are monitored dependent on an
applied electrochemical potential. We developed a bleaching model that yields the lowest
electronic state in the conduction band of the nanostructures. A change in the band
edge positions caused by quantum confinement is shown both for CdSe quantum dots as
well as for colloidal nanoplatelets. In the case of CdSe quantum dots these findings are
in good agreement with tight binding calculations. The method presented is not limited
to CdSe nanostructures but can be used as a universal tool. Hence, this technique allows
the determination of absolute band edge positions of a large variety of materials used in
various applications.
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Accepted manuscript
Citation
Spittel D, Poppe J, Meerbach C et al (2018) Absolute Energy Level Positions in CdSe Nanostructures from Potential-Modulated Absorption Spectroscopy (EMAS). ACS Nano. 11(12): 12174-12184.
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