Spectroscopic Identification of the Charge Transfer State in Thiophene/Fullerene Heterojunctions: Electroabsorption Spectroscopy from GW/BSE Calculations
Citation:
Sahoo, Smruti Ranjan, Patterson, Charles H., Spectroscopic Identification of the Charge Transfer State in Thiophene/Fullerene Heterojunctions: Electroabsorption Spectroscopy from GW/BSE Calculations, The Journal of Physical Chemistry C, 127, 32, 2023, 15928-15942Download Item:
Abstract:
Creation of charge transfer (CT) states in bulk heterojunction systems such as C60/polymer blends is an
important intermediate step in creation of carriers in organic photovoltaic systems. CT states generally have small
oscillator strengths in linear optical absorption spectroscopy owing to limited spatial overlap of electron and hole wave
functions in the CT excited state. Electroabsorption spectroscopy (EA) exploits changes in wave function character
of CT states in response to static electric fields to enhance detection of CT states via nonlinear optical absorption
spectroscopies. A 4x4 model Hamiltonian is used to derive splittings of even and odd Frenkel (FR) excited states and
changes in wave function character of CT excited states in an external electric field. These are used to explain why FR
and CT states yield EA lineshapes which are first and second derivatives of the linear optical absorption spectrum. The
model is applied to ammonia-borane molecules and pairs of molecules with large and small B-N separations and CT
or FR excited states. EA spectra are obtained from differences in linear optical absorption spectra in the presence or
absence of a static electric field and from perturbative sum over states (SOS) configuration interaction singles
χ(2) andχ(3) nonlinear susceptibility calculations. Good agreement is found between finite field (FF) and SOS methods at field
strengths similar to those used in EA experiments. EA spectra of three C60/oligothiophene complexes are calculated
using the SOS method combined with GW /BSE methods. For these C60/oligothiophene complexes we find several CT
states in a narrow energy range in which charge transfer from the thiophene HOMO level to several closely spaced C60
acceptor levels yields an EA signal around 10% of the signal from oligothiophene.
Sponsor
Grant Number
Irish Research Council (IRC)
GOIPD/2020/792
Science Foundation Ireland (SFI)
19/FFP/6582
Author's Homepage:
http://people.tcd.ie/cpttrsonDescription:
PUBLISHED
Author: Patterson, Charles
Sponsor:
Irish Research Council (IRC)Science Foundation Ireland (SFI)
Type of material:
Journal ArticleCollections
Series/Report no:
The Journal of Physical Chemistry C127
32
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Full text availableSubject (TCD):
Condensed matter, optical and dielectric properties , FULLERENES AND DERIVATIVES , Photovoltaic systems, cells and modules manufacturing , Theory and computational physicsDOI:
https://doi.org/10.1021/acs.jpcc.3c03734ISSN:
1932-7447Metadata
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