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

Matsuzaki, Hiroyuki, Furube, Akihiro, Katoh, Ryuzi, Singh, Samarendra Pratap, Sonar, Prashant, Williams, Evan Laurence, Vijila, Chellappan, Subramanian, Gomathy Sandhya, Gorelik, Sergey, & Hobley, Jonathan (2014) Excited-state dynamics in diketopyrrolopyrrole-based copolymer for organic photovoltaics investigated by transient optical spectroscopy. Japanese Journal of Applied Physics, 53(1S), 01AB11-1.

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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.

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ID Code: 75230
Item Type: Journal Article
Refereed: Yes
Keywords: Donor-acceptor copolymers, Femtosecond transient absorption measurements, Femtosecond transient absorption spectroscopy, Fluorescence intensities, Fluorescence measurements, Singlet-singlet annihilation, Time-resolved fluorescence, Transient optical spectroscopy, Copolymers, Excitons, Naphthalene, Nuclear physics, Photobleaching, Rate constants, Fluorescence
DOI: 10.7567/JJAP.53.01AB11
ISSN: 0021-4922
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2014 The Japan Society of Applied Physics.
Deposited On: 08 Oct 2014 22:51
Last Modified: 17 Feb 2015 06:57

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