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Title: Long-lived charge carrier generation in ordered films of a covalent perylenediimide–diketopyrrolopyrrole–perylenediimide molecule

The photophysics of a covalently linked perylenediimide–diketopyrrolopyrrole–perylenediimide acceptor–donor–acceptor molecule (PDI–DPP–PDI, 1) were investigated and found to be markedly different in solution versus in unannealed and solvent annealed films. Photoexcitation of 1 in toluene results in quantitative charge separation in τ = 3.1 ± 0.2 ps, with charge recombination in τ = 340 ± 10 ps, while in unannealed/disordered films of 1, charge separation occurs in τ < 250 fs, while charge recombination displays a multiexponential decay in ~6 ns. The absence of long-lived, charge separation in the disordered film suggests that few free charge carriers are generated. In contrast, upon CH₂Cl₂ vapor annealing films of 1, grazing-incidence X-ray scattering shows that the molecules form a more ordered structure. Photoexcitation of the ordered films results in initial formation of a spin-correlated radical ion pair (electron–hole pair) as indicated by magnetic field effects on the formation of free charge carriers which live for ~4 μs. This result has significant implications for the design of organic solar cells based on covalent donor–acceptor systems and shows that long-lived, charge-separated states can be achieved by controlling intramolecular charge separation dynamics in well-ordered systems.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Northwestern Univ., Evanston, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; FG02-99ER14999
Type:
Accepted Manuscript
Journal Name:
Chemical Science
Additional Journal Information:
Journal Volume: 6; Journal Issue: 1; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 14 SOLAR ENERGY
OSTI Identifier:
1164941

Hartnett, Patrick E., Dyar, Scott M., Margulies, Eric A., Shoer, Leah E., Cook, Andrew W., Eaton, Samuel W., Marks, Tobin J., and Wasielewski, Michael R.. Long-lived charge carrier generation in ordered films of a covalent perylenediimide–diketopyrrolopyrrole–perylenediimide molecule. United States: N. p., Web. doi:10.1039/C4SC02551B.
Hartnett, Patrick E., Dyar, Scott M., Margulies, Eric A., Shoer, Leah E., Cook, Andrew W., Eaton, Samuel W., Marks, Tobin J., & Wasielewski, Michael R.. Long-lived charge carrier generation in ordered films of a covalent perylenediimide–diketopyrrolopyrrole–perylenediimide molecule. United States. doi:10.1039/C4SC02551B.
Hartnett, Patrick E., Dyar, Scott M., Margulies, Eric A., Shoer, Leah E., Cook, Andrew W., Eaton, Samuel W., Marks, Tobin J., and Wasielewski, Michael R.. 2015. "Long-lived charge carrier generation in ordered films of a covalent perylenediimide–diketopyrrolopyrrole–perylenediimide molecule". United States. doi:10.1039/C4SC02551B. https://www.osti.gov/servlets/purl/1164941.
@article{osti_1164941,
title = {Long-lived charge carrier generation in ordered films of a covalent perylenediimide–diketopyrrolopyrrole–perylenediimide molecule},
author = {Hartnett, Patrick E. and Dyar, Scott M. and Margulies, Eric A. and Shoer, Leah E. and Cook, Andrew W. and Eaton, Samuel W. and Marks, Tobin J. and Wasielewski, Michael R.},
abstractNote = {The photophysics of a covalently linked perylenediimide–diketopyrrolopyrrole–perylenediimide acceptor–donor–acceptor molecule (PDI–DPP–PDI, 1) were investigated and found to be markedly different in solution versus in unannealed and solvent annealed films. Photoexcitation of 1 in toluene results in quantitative charge separation in τ = 3.1 ± 0.2 ps, with charge recombination in τ = 340 ± 10 ps, while in unannealed/disordered films of 1, charge separation occurs in τ < 250 fs, while charge recombination displays a multiexponential decay in ~6 ns. The absence of long-lived, charge separation in the disordered film suggests that few free charge carriers are generated. In contrast, upon CH₂Cl₂ vapor annealing films of 1, grazing-incidence X-ray scattering shows that the molecules form a more ordered structure. Photoexcitation of the ordered films results in initial formation of a spin-correlated radical ion pair (electron–hole pair) as indicated by magnetic field effects on the formation of free charge carriers which live for ~4 μs. This result has significant implications for the design of organic solar cells based on covalent donor–acceptor systems and shows that long-lived, charge-separated states can be achieved by controlling intramolecular charge separation dynamics in well-ordered systems.},
doi = {10.1039/C4SC02551B},
journal = {Chemical Science},
number = 1,
volume = 6,
place = {United States},
year = {2015},
month = {7}
}