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  4. Critical role of H-aggregation for high-efficiency photoinduced charge generation in pristine pentamethine cyanine salts
 
research article

Critical role of H-aggregation for high-efficiency photoinduced charge generation in pristine pentamethine cyanine salts

Fish, George C.  
•
Moreno-Naranjo, Juan Manuel
•
Billion, Andreas
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October 8, 2021
Physical Chemistry Chemical Physics

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.

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Type
research article
DOI
10.1039/D1CP03251H
Author(s)
Fish, George C.  
Moreno-Naranjo, Juan Manuel
Billion, Andreas
Kratzert, Daniel
Hack, Erwin
Krossing, Ingo  
Nüesch, Frank  
Moser, Jacques-E.  
Date Issued

2021-10-08

Published in
Physical Chemistry Chemical Physics
Volume

23

Start page

23886

End page

23895

Subjects

Cyanine dyes

•

Molecular aggregation

•

Organic salts semiconductors

•

Symmetry-breaking photoinduced charge separation

•

Weakly-coordinating anions

•

Ultrafast spectroscopy

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
GR-MO  
IMX  
FunderGrant Number

FNS

200021_175729

FNS-NCCR

MUST Phase III

RelationURL/DOI

IsSupplementedBy

https://infoscience.epfl.ch/record/290028

IsSupplementedBy

10.5281/zenodo.5681239
Available on Infoscience
October 27, 2021
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/182579
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