Solid-state-concentration effects on the optical absorption and emission of poly({ital p}-phenylene vinylene)-related materials
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
- Department of Physics and Centre for Molecular Materials, University of Sheffield, Sheffield S3 7RH (United Kingdom)
- Dyson Perrins Laboratory, Oxford University, Oxford OX1 3QY (United Kingdom)
- The University of Texas at Dallas, Richardson, Texas 75080 (United States)
- Max-Planck-Institut fuer Polymerforschung, Mainz (Germany)
We present measurements of the optical absorption and emission properties of poly({ital p}-phenylene vinylene) (PPV) -related materials focusing on the differences between molecules isolated by dispersion in an inert host and concentrated molecular films. Optical absorption spectra, photoluminescence (PL) spectra, PL efficiency, and time-resolved PL spectra of dilute blends of PPV oligomers with 2{endash}5 phenylene-phenyl rings are compared with those of dense oligomer and polymer films. In dilute oligomer-poly(methyl methacrylate) (PMMA) blends with high PL efficiency, the PL decay is exponential, independent of both temperature and oligomer length. This implies that the fundamental radiative lifetime of PPV oligomers is essentially independent of oligomer length. Concentrated spin-cast oligomer films and polymers have a faster and strongly temperature-dependent PL decay that approaches that of the dilute oligomer results at low temperature. The differences in PL decay correspond to changes in PL efficiency. The efficiency of the oligomer-PMMA blend is high and only weakly temperature dependent, whereas that of concentrated films is lower and strongly temperature dependent, decreasing by more than a factor of 3 from 10 to 350 K. The quenching of the PL efficiency in concentrated films is due to migration to extrinsic, impurity related centers as opposed to an intrinsic intermolecular recombination process. The PL spectrum of a dilute oligomer blend redshifts substantially, both as the excitation energy is decreased and as the emission time increases. This spectral redshift is due to disorder-induced site-to-site variation and not to diffusion to lower-energy sites. In contrast, no spectral shift with excitation energy or emission time was observed for dense oligomer films. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 392708
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 54, Issue 8; Other Information: PBD: Aug 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
Synthesis and electroluminescence study of a novel copolymer: Poly(phenylene vinylene-co-quinoline vinylene)
Use of solid state NMR to probe the order, dynamics and conformations of poly(p-phenylene vinylene) and poly(2,5-dimethoxy-p-phenylene vinylene). [NMR (nuclear magnetic resonance)]