Excited-state dynamics in diketopyrrolopyrrole-based copolymer for organic photovoltaics investigated by transient optical spectroscopy

Hiroyuki Matsuzaki, Akihiro Furube, Ryuzi Katoh, Samarendra Pratap Singh, Prashant Sonar, Evan Laurence Williams, Chellappan Vijila, Gomathy Sandhya Subramanian, Sergey Gorelik, Jonathan Hobley

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4 Citations (Scopus)

Abstract

We investigate the photoexcited state dynamics in a donor-acceptor copolymer, poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]- pyrrole-1,4-dione-alt-naphthalene} (pDPP-TNT), by picosecond fluorescence and femtosecond transient absorption spectroscopies. Timeresolved fluorescence lifetime measurements of pDPP-TNT thin films reveal that the lifetime of the singlet excited state is 185 ± 5 ps and that singlet-singlet annihilation occurs at excitation photon densities above 6 × 1017 photons/cm3. From the results of singlet-singlet annihilation analysis, we estimate that the single-singlet annihilation rate constant is (6.0 ± 0.2) × 109cm3 s-1 and the singlet diffusion length is -7 nm. From the comparison of femtosecond transient absorption measurements and picosecond fluorescence measurements, it is found that the time profile of the photobleaching signal in the charge-transfer (CT) absorption band coincides with that of the fluorescence intensity and there is no indication of long-lived species, which clearly suggests that charged species, such as polaron pairs and triplet excitons, are not effectively photogenerated in the neat pDPP-TNT polymer.

Original languageEnglish
Article number01AB11
JournalJapanese journal of applied physics
Volume53
Issue number1 PART 2
DOIs
Publication statusPublished - 2014

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physics and Astronomy(all)

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