Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Photoluminescence of poly(p-phenylenevinylene)-silica nanocomposites: Evidence for dual emission by Franck-Condon analysis
Autore:
Ho, PKH; Kim, JS; Tessler, N; Friend, RH;
Indirizzi:
Univ Cambridge, Cavendish Lab, Cambridge CB3 0HE, England Univ Cambridge Cambridge England CB3 0HE Lab, Cambridge CB3 0HE, England Technion Israel Inst Technol, Dept Elect Engn, IL-3200 Haifa, Israel Technion Israel Inst Technol Haifa Israel IL-3200 IL-3200 Haifa, Israel
Titolo Testata:
JOURNAL OF CHEMICAL PHYSICS
fascicolo: 6, volume: 115, anno: 2001,
pagine: 2709 - 2720
SICI:
0021-9606(20010808)115:6<2709:POPNE>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
SITE-SELECTIVE FLUORESCENCE; LIGHT-EMITTING-DIODES; PHENYLENE VINYLENE OLIGOMERS; CONJUGATED POLYMERS; SEMICONDUCTING POLYMERS; INTERCHAIN INTERACTIONS; OPTICAL-ABSORPTION; THIN-FILMS; SPECTRA; EXCITON;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
66
Recensione:
Indirizzi per estratti:
Indirizzo: Ho, PKH Univ Cambridge, Cavendish Lab, Madingley Rd, Cambridge CB3 0HE, England Univ Cambridge Madingley Rd Cambridge England CB3 0HE HE, England
Citazione:
P.K.H. Ho et al., "Photoluminescence of poly(p-phenylenevinylene)-silica nanocomposites: Evidence for dual emission by Franck-Condon analysis", J CHEM PHYS, 115(6), 2001, pp. 2709-2720

Abstract

The vibronic mode intensity pattern of the photoluminescence (PL) spectra of poly(p-phenylenevinylene) (PPV) nanocomposites dispersed with 5-nm-diam silica particles shows an apparent redistribution toward the nominal 0-0 mode with increasing silica volume fraction. Franck-Condon analysis of this variation, corrected for refractive index dispersion, reveals the presence of overlapping emission from two excited electronic states separated by 180 meV. The principal emission arises from the molecular exciton while the lower-lying one is assigned to a dipole-dipole coupled two-chain aggregate exciton. The quantum yield of the aggregate emission decreases monotonically with silica loading up to 50 vol %, whereas that of the molecular state exhibits a maximum at 15 vol %. When the samples are photoexcited below the pi-pi (*) localization edge, both of these emissions jointly redshift without a change in their relative intensities. When cooled below a transition temperature centered at 120 K, the yield of the aggregate exciton decreases sharply relative to the molecular exciton and the overall PL quantum yield (eta (pl)) rises. The aggregate exciton therefore appears to be formed from the molecular exciton through a phonon-assisted mechanism. At room temperature, this directly competes with de-excitation of the molecular exciton. Thisbehavior differs from the dialkoxy-PPVs which show site-selective excitation and thus direct population of the aggregate domains. Using classical dielectric medium theories to correct for the effects of refractive index, theradiative lifetime (tau (r)) of the molecular exciton in the various PPV compositions can be estimated. Together with the experimentally determined eta (pl), this gives the eta (pl)tau (r) product of the molecular exciton asa function of composition. This function exhibits a maximum at 15 vol % silica, indicative of a crossover behavior that shows the competing influenceof morphological disorder on the population and radiative de-excitation ofthis state. (C) 2001 American Institute of Physics.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 01/12/20 alle ore 12:21:27