Unravelling the mechanism of high efficiency photoinduced charge generation in pentamethine cyanine dye films

Abstract: The mechanism of photoinduced symmetry-breaking charge separation in solid cyanine salts at the base of organic photovoltaic and optoelectronic devices is still debated. Here, we employ femtosecond transient absorption spectroscopy (TAS) to monitor the charge transfer processes occurring in thin films of pristine pentamethine cyanine (Cy5). Oxidized dye species are observed in Cy5-hexafluorophosphate salts upon photoexcitation, resulting from electron transfer from monomer excited states to H-aggregates. The charge separation proceeds with a quantum yield of 86%, providing the first direct proof of high efficiency intrinsic charge generation in organic salt semiconductors. The impact of the size of weakly coordinating anions on charge separation and transport is studied using TAS alongside electroabsorption spectroscopy and time-of-flight techniques. The degree of H-aggregation decreases with increasing anion size, resulting in reduced charge transfer. However, there is little change in carrier mobility, as despite the interchromophore distance increasing, the decrease in energetic disorder helps to alleviate the trapping of charges by H-aggregates

Location
Deutsche Nationalbibliothek Frankfurt am Main
Extent
Online-Ressource
Notes
Physical chemistry, chemical physics. - 23, 41 (2021) , 23886-23895, ISSN: 1463-9084

Event
Veröffentlichung
(where)
Freiburg
(who)
Universität
(when)
2021
Creator
Fish, George C.
Moreno-Naranjo, Juan Manuel
Billion, Andreas
Kratzert, Daniel
Hack, Erwin
Krossing, Ingo
Nüesch, Frank
Moser, Jacques-E

DOI
10.1039/D1CP03251H
URN
urn:nbn:de:bsz:25-freidok-2225455
Rights
Kein Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
Last update
25.03.2025, 1:54 PM CET

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Associated

Time of origin

  • 2021

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