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Title: Exciton Absorption Spectra by Linear Response Methods: Application to Conjugated Polymers

Abstract

The theoretical description of the time-evolution of excitons requires, as an initial step, the calculation of their spectra, which has been inaccessible to most users due to the high computational scaling of conventional algorithms and accuracy issues caused by common density functionals. Previously (J. Chem. Phys.2016, 144, 204105), we developed a simple method that resolves these issues. Our scheme is based on a two-step calculation in which a linear-response TDDFT calculation is used to generate orbitals perturbed by the excitonic state, and then a second linear-response TDDFT calculation is used to determine the spectrum of excitations relative to the excitonic state. Herein, we apply this theory to study near-infrared absorption spectra of excitons in oligomers of the ubiquitous conjugated polymers poly(3-hexylthiophene) (P3HT), poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV), and poly(benzodithiophene-thieno[3,4-b]thiophene) (PTB7). For P3HT and MEH-PPV oligomers, the calculated intense absorption bands converge at the longest wavelengths for 10 monomer units, and show strong consistency with experimental measurements. The calculations confirm that the exciton spectral features in MEH-PPV overlap with those of the bipolaron formation. In addition, our calculations identify the exciton absorption bands in transient absorption spectra measured by our group for oligomers (1, 2, and 3 units) of PTB7. For all of themore » cases studied, we report the dominant orbital excitations contributing to the optically active excited state–excited state transitions, and suggest a simple rule to identify absorption peaks at the longest wavelengths. We suggest our methodology could be considered for further developments in theoretical transient spectroscopy to include nonadiabatic effects, coherences, and to describe the formation of species such as charge-transfer states and polaron pairs.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1];  [1];  [2]; ORCiD logo [1];  [1]
  1. Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry and the Materials Research Center
  2. Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry and the Materials Research Center; Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Argonne-Northwestern Solar Energy Research Center (ANSER)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1388123
Grant/Contract Number:  
SC0001059
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 139; Journal Issue: 10; Related Information: ANSER partners with Northwestern University (lead); Argonne National Laboratory; University of Chicago; University of Illinois, Urbana-Champaign; Yale University; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; catalysis (homogeneous); catalysis (heterogeneous); solar (photovoltaic); solar (fuels); photosynthesis (natural and artificial); bio-inspired; hydrogen and fuel cells; electrodes - solar; defects; charge transport; spin dynamics; membrane; materials and chemistry by design; optics; synthesis (novel materials); synthesis (self-assembly)

Citation Formats

Mosquera, Martín A., Jackson, Nicholas E., Fauvell, Thomas J., Kelley, Matthew S., Chen, Lin X., Schatz, George C., and Ratner, Mark A. Exciton Absorption Spectra by Linear Response Methods: Application to Conjugated Polymers. United States: N. p., 2017. Web. doi:10.1021/jacs.6b12405.
Mosquera, Martín A., Jackson, Nicholas E., Fauvell, Thomas J., Kelley, Matthew S., Chen, Lin X., Schatz, George C., & Ratner, Mark A. Exciton Absorption Spectra by Linear Response Methods: Application to Conjugated Polymers. United States. doi:10.1021/jacs.6b12405.
Mosquera, Martín A., Jackson, Nicholas E., Fauvell, Thomas J., Kelley, Matthew S., Chen, Lin X., Schatz, George C., and Ratner, Mark A. Wed . "Exciton Absorption Spectra by Linear Response Methods: Application to Conjugated Polymers". United States. doi:10.1021/jacs.6b12405. https://www.osti.gov/servlets/purl/1388123.
@article{osti_1388123,
title = {Exciton Absorption Spectra by Linear Response Methods: Application to Conjugated Polymers},
author = {Mosquera, Martín A. and Jackson, Nicholas E. and Fauvell, Thomas J. and Kelley, Matthew S. and Chen, Lin X. and Schatz, George C. and Ratner, Mark A.},
abstractNote = {The theoretical description of the time-evolution of excitons requires, as an initial step, the calculation of their spectra, which has been inaccessible to most users due to the high computational scaling of conventional algorithms and accuracy issues caused by common density functionals. Previously (J. Chem. Phys.2016, 144, 204105), we developed a simple method that resolves these issues. Our scheme is based on a two-step calculation in which a linear-response TDDFT calculation is used to generate orbitals perturbed by the excitonic state, and then a second linear-response TDDFT calculation is used to determine the spectrum of excitations relative to the excitonic state. Herein, we apply this theory to study near-infrared absorption spectra of excitons in oligomers of the ubiquitous conjugated polymers poly(3-hexylthiophene) (P3HT), poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV), and poly(benzodithiophene-thieno[3,4-b]thiophene) (PTB7). For P3HT and MEH-PPV oligomers, the calculated intense absorption bands converge at the longest wavelengths for 10 monomer units, and show strong consistency with experimental measurements. The calculations confirm that the exciton spectral features in MEH-PPV overlap with those of the bipolaron formation. In addition, our calculations identify the exciton absorption bands in transient absorption spectra measured by our group for oligomers (1, 2, and 3 units) of PTB7. For all of the cases studied, we report the dominant orbital excitations contributing to the optically active excited state–excited state transitions, and suggest a simple rule to identify absorption peaks at the longest wavelengths. We suggest our methodology could be considered for further developments in theoretical transient spectroscopy to include nonadiabatic effects, coherences, and to describe the formation of species such as charge-transfer states and polaron pairs.},
doi = {10.1021/jacs.6b12405},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 10,
volume = 139,
place = {United States},
year = {2017},
month = {2}
}

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