Theoretical studies on conjugated phenyl-cored thiophene dendrimers for photovoltaic applications

Muhammet E. Köse, William J. Mitchell, Nikos Kopidakis, Christopher H. Chang, Sean E. Shaheen, Kwiseon Kim, Gary Rumbles

Research output: Contribution to journalArticle

124 Citations (Scopus)

Abstract

π-Conjugated dendrimers are an important class of materials for optoelectronic devices, especially for light-harvesting systems. We report here a theoretical investigation of the optical response and of the excited-state properties of three-arm and four-arm phenyl-cored dendrimers for photovoltaic applications. A variety of theoretical methods are used and evaluated against each other to calculate vertical transition energies, absorption and excitation spectra with vibronic structure, charge transport, and excitonic behavior upon photoexcitation and photoemission processes. Photophysical phenomena in these dendrimers are, in general, better explained with ab initio methods rather than with semiempirical techniques. Calculated reorganization energies were found to correlate well with the device photocurrent data where available. The excitons formed during photoexcitation are calculated to be more delocalized than the ones formed after vibrational relaxation in the excited states for fluorescence emission. The localization of excitons in emission processes is a result of geometrical changes in the excited state coupled with vibronic modes. Correlated electron-hole pair diagrams illustrate breaking of π-conjugation in three-arm dendrimers due to meta linkage of arms with the core, whereas four-arm dendrimers are not affected by such breaking due to presence of ortho and para branching. Yet, ortho branching causes large twist angles between the core and the arms that are detrimental to π-electron system delocalization over the structure.

Original languageEnglish
Pages (from-to)14257-14270
Number of pages14
JournalJournal of the American Chemical Society
Volume129
Issue number46
DOIs
Publication statusPublished - Nov 21 2007

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Dendrimers
Thiophenes
Thiophene
Theoretical Models
Excited states
Photoexcitation
Excitons
Electrons
Equipment and Supplies
Energy absorption
Photoemission
Photocurrents
Optoelectronic devices
Charge transfer
Fluorescence
Light

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Theoretical studies on conjugated phenyl-cored thiophene dendrimers for photovoltaic applications. / Köse, Muhammet E.; Mitchell, William J.; Kopidakis, Nikos; Chang, Christopher H.; Shaheen, Sean E.; Kim, Kwiseon; Rumbles, Gary.

In: Journal of the American Chemical Society, Vol. 129, No. 46, 21.11.2007, p. 14257-14270.

Research output: Contribution to journalArticle

Köse, Muhammet E. ; Mitchell, William J. ; Kopidakis, Nikos ; Chang, Christopher H. ; Shaheen, Sean E. ; Kim, Kwiseon ; Rumbles, Gary. / Theoretical studies on conjugated phenyl-cored thiophene dendrimers for photovoltaic applications. In: Journal of the American Chemical Society. 2007 ; Vol. 129, No. 46. pp. 14257-14270.
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