Photoexcited states in poly(p-phenylene vinylene): Comparison withtrans,trans-distyrylbenzene, a model oligomer
- 15 December 1990
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 42 (18), 11670-11681
- https://doi.org/10.1103/physrevb.42.11670
Abstract
We present measurements of the photoexcited states of poly(p-phenylene vinylene), PPV, and a model oligomer, trans,trans-distyrylbenzene, probed by detection of photoluminescence and photoinduced absorption. Photoluminescence is strong in both materials and due to radiative recombination of the singlet exciton. Triplet excitons are also photogenerated, and in the case of the oligomer are seen directly in light-induced ESR measurements. We find a signal with a peak-to-peak width of 12 G at 1580 G for a probe frequency of 9.14 GHz. We assign this to the ‘‘forbidden’’ Δ=2 transition between the triplet sublevels. From the position of the minimum field for this microwave transition, we determine the zero-field splitting of the triplet sublevels to be 0.07 . We find an associated photoinduced absorption at 1.95 eV in the oligomer which we attribute to a triplet-triplet transition of the excited state. For the polymer we find a photoinduced absorption response at 1.45 eV, very similar to that of the oligomer, and we consider that this is similarly due to a triplet exciton, although we have not been able yet to find direct ESR evidence. In the case of the polymer, charged photoexcitations are also seen in photoinduced absorption measurements, characteristic of bipolarons, with induced absorption at 0.6 and 1.6 eV. We do not find similar excitations in the oligomer, and we consider that intermolecular charge transport is necessary for the generation of the long-lived charged excitations probed in our experiments.
Keywords
This publication has 36 references indexed in Scilit:
- Photoexcited states in poly(3-alkyl thienylenes)Journal of Physics: Condensed Matter, 1990
- Spectroscopic and cyclic voltammetric studies of poly(p-phenylene vinylene) prepared from two different sulphonium salt precursor polymersPolymer, 1989
- Excited states and their relaxation dynamics intrans-polyacetylenePhysical Review B, 1989
- Photoexcitation in poly(p-phenylene vinylene)Synthetic Metals, 1989
- Mechanism for photogeneration of metastable charged solitons in polyacetylenePhysical Review B, 1988
- Ultraviolet and visible spectroscopy of poly(paraphenylene vinylene)The Journal of Chemical Physics, 1987
- Correlation between conjugation length and non-radiative relaxation rate in poly(p-phenylene vinylene): a picosecond photoluminescence studyJournal of Physics C: Solid State Physics, 1987
- Molecular orientation and conductivity in highly drawn poly(p-phenylene vinylene)Synthetic Metals, 1987
- Structure investigation of poly(p‐phenylene vinylene)Journal of Polymer Science Part B: Polymer Physics, 1986
- Oligomere als modelle für poly‐p‐xylyliden. Untersuchungen über stilbene. XLIX.1Die Makromolekulare Chemie, 1970