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

Authors :
Akihiro Furube
Gomathy Sandhya Subramanian
Jonathan Hobley
Samarendra P. Singh
Ryuzi Katoh
Evan L. Williams
Hiroyuki Matsuzaki
Sergey Gorelik
Chellappan Vijila
Prashant Sonar
Source :
Japanese Journal of Applied Physics. 53:01AB11
Publication Year :
2013
Publisher :
IOP Publishing, 2013.

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. Time-resolved 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) × 10−9 cm3 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.

Details

ISSN :
13474065 and 00214922
Volume :
53
Database :
OpenAIRE
Journal :
Japanese Journal of Applied Physics
Accession number :
edsair.doi...........ef2a2c00cb7557a2ffeabad401b9a884