Entropy and disorder enable charge separation in organic solar cells

Hood, Samantha N. and Kassal, Ivan (2016) Entropy and disorder enable charge separation in organic solar cells. Journal of Physical Chemistry Letters, 7 22: 4495-4500. doi:10.1021/acs.jpclett.6b02178


Author Hood, Samantha N.
Kassal, Ivan
Title Entropy and disorder enable charge separation in organic solar cells
Journal name Journal of Physical Chemistry Letters   Check publisher's open access policy
ISSN 1948-7185
Publication date 2016-11-17
Sub-type Article (original research)
DOI 10.1021/acs.jpclett.6b02178
Open Access Status Not yet assessed
Volume 7
Issue 22
Start page 4495
End page 4500
Total pages 6
Place of publication Washington, DC, United States
Publisher American Chemical Society
Language eng
Abstract Although organic heterojunctions can separate charges with near-unity efficiency and on a subpicosecond time scale, the full details of the charge-separation process remain unclear. In typical models, the Coulomb binding between the electron and the hole can exceed the thermal energy kBT by an order of magnitude, suggesting that it is impossible for the charges to separate before recombining. Here, we consider the entropic contribution to charge separation in the presence of disorder and find that even modest amounts of disorder have a decisive effect, reducing the charge-separation barrier to about kBT or eliminating it altogether. Therefore, the charges are usually not thermodynamically bound at all and could separate spontaneously if the kinetics otherwise allowed it. Our conclusion holds despite the worst-case assumption of localized, thermalized carriers and is only strengthened if mechanisms like delocalization or "hot" states are also present.
Formatted abstract
Although organic heterojunctions can separate charges with near-unity efficiency and on a subpicosecond time scale, the full details of the charge-separation process remain unclear. In typical models, the Coulomb binding between the electron and the hole can exceed the thermal energy kBT by an order of magnitude, suggesting that it is impossible for the charges to separate before recombining. Here, we consider the entropic contribution to charge separation in the presence of disorder and find that even modest amounts of disorder have a decisive effect, reducing the charge-separation barrier to about kBT or eliminating it altogether. Therefore, the charges are usually not thermodynamically bound at all and could separate spontaneously if the kinetics otherwise allowed it. Our conclusion holds despite the worst-case assumption of localized, thermalized carriers and is only strengthened if mechanisms like delocalization or "hot" states are also present.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
HERDC Pre-Audit
 
Versions
Version Filter Type
Citation counts: Scopus Citation Count Cited 13 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Tue, 06 Dec 2016, 10:53:00 EST by System User on behalf of Learning and Research Services (UQ Library)