Charge and energy transport in films of touching nanocrystals
2017-05
Loading...
View/Download File
Persistent link to this item
Statistics
View StatisticsJournal Title
Journal ISSN
Volume Title
Title
Charge and energy transport in films of touching nanocrystals
Authors
Published Date
2017-05
Publisher
Type
Presentation
Abstract
This talk deals with films of nanocrystals (NC), which touch each other by small facets with radius ρ. First I calculate the matrix element for electron tunneling from one NC to another and show that it is proportional to ρ3. I use this matrix element to calculate two transport properties of NC films: conductivity and exciton diffusion length.
In the first case I focus on the critical concentration of electrons for the insulator-metal transition (IMT) in the film. The famous Mott's criterion answers this question only in bulk materials. The same critical concentration as in a bulk material is not sufficient for the IMT in NC films because of the weak coupling between NCs. For IMT in NC films, one needs much larger concentration at which the typical electron wave packet becomes smaller than the facet radius ρ and can pass through the facet. The predicted critical concentration is proportional to 1/ρ3 and is in good agreement with experimental data obtained by Kortshagen's group for silicon NC films.
In the second part of the talk, I consider the exciton diffusion length in NC films. In photovoltaic devices based on NC films, absorption of a light quantum creates of an exciton (electron-hole pair) in a NC. The diffusion length of an exciton is important parameter determining the volume from which photons are harvested. It is known that an exciton can hop between nearest-neighbor NC via the Forster mechanism. For touching NC, I propose another mechanism where the electron and hole tunnel through the small contact facet in tandem. The tandem tunneling occurs through the intermediate state in which the electron and hole are in different NCs. I show that for majority of materials the tandem tunneling exciton transfer rate is comparable with the Forster rate, while for silicon the tandem tunneling dominates.
Description
Related to
Replaces
License
Series/Report Number
Funding information
Isbn identifier
Doi identifier
Previously Published Citation
Suggested citation
Reich, Kostya. (2017). Charge and energy transport in films of touching nanocrystals. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/188125.
Content distributed via the University Digital Conservancy may be subject to additional license and use restrictions applied by the depositor. By using these files, users agree to the Terms of Use. Materials in the UDC may contain content that is disturbing and/or harmful. For more information, please see our statement on harmful content in digital repositories.