Ultraviolet--visible near-field microscopy of phase-separated blends of polyfluorene-based conjugated semiconductors
We have used fluorescence scanning near-field microscopy to characterize polymer blends for electroluminescent applications, and thereby identify compositional nonhomogeneities. In particular, we have focused on the binary system constituted by poly(9,9{prime}-dioctylfluorenealt-benzothiadiazole) and poly(9,9{prime}-dioctylfluorene) (PFO), known to give efficiencies of up to 22 cd/A in light-emitting devices with suitable electrodes. Our primary aim was the assignment of the morphological features revealed in shear-force and atomic-force images of spin-coated films, and suggestive of phase separation on a 300-nm-length scale. From analysis of the fluorescence images (325 and 488 nm excitation), and quantitative correlation of optical and topographic data, we identify the raised features with PFO-rich regions. However, the limited variation in fluorescence intensity reveals a high extent of mixing within each phase on the length scale accessible in our experiment, approximately 100 nm for our focused-ion-beam-processed probe apertures. {copyright} 2001 American Institute of Physics.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40230720
- Journal Information:
- Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 6 Vol. 79; ISSN 0003-6951
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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