Charge-transfer character of excitons in poly[2,7-(9,9-di-n-octylfluorene)((1-x))-co-4,7-(2,1,3-benzothiadiazole) ((x))]
- Authors
- Winfield, Jessica M.; Van Vooren, Antoine; Park, Moo-Jin; Hwang, Do-Hoon; Cornil, Jerome; Kim, Ji-Seon; Friend, Richard H.
- Issue Date
- 21-Jul-2009
- Publisher
- AMER INST PHYSICS
- Keywords
- charge exchange; excited states; excitons; oscillator strengths; photoluminescence; polymer blends; spectral line shift
- Citation
- JOURNAL OF CHEMICAL PHYSICS, v.131, no.3
- Journal Title
- JOURNAL OF CHEMICAL PHYSICS
- Volume
- 131
- Number
- 3
- URI
- https://scholarworks.bwise.kr/kumoh/handle/2020.sw.kumoh/27310
- DOI
- 10.1063/1.3177327
- ISSN
- 0021-9606
1089-7690
- Abstract
- Quantum-chemical calculations performed on poly[2,7-(9,9-di-n-octylfluorene)((1-x))-co-4,7-(2,1,3-benzothiadiazole)((x))] copolymers (0 < x < 0.5) show that the lowest unoccupied molecular orbital is always highly localized on the benzothiadiazole (BT) units while the highest occupied molecular orbital is delocalized over the whole chain. Chains with a low BT content are characterized by a reduced oscillator strength of the lowest optical transition and by an increased charge-transfer character of the exciton. These results are supported experimentally by a blueshift of the lowest energy absorption band upon reduction in the BT ratio, lower photoluminescence efficiency, longer excited state lifetimes, and greater solvent dependence of the emission properties.
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