Magnetic resonance spectroscopy of fullerenes and {pi}-conjugated polymers

Thesis/Dissertation · Thu Oct 20 04:00:00 EDT 1994

OSTI ID:50891

Lane, P A

Photophysics of two {pi}-conjugated systems, buckminsterfullerene and {pi}-conjugated polymers, were studied using photoluminescence-detected magnetic resonance (PLDMR). PLDMR of C{sub 60} and C{sub 70} dissolved in toluene/polystyrene glasses and of fullerene films is described. PLDMR of the glasses is due to a triplet exciton delocalized over the entire molecule; that of {sup 3}C{sub 70} differs from {sup 3}C{sub 60} due to its longer triplet lifetime. In the films, the delocalized triplet, distorted by intermolecular interactions, reveals a half-field resonance due to triplet-triplet fusion; a second triplet localized on a pentagon or hexagon face next to a neighbor molecule is also detected. Narrow PL-enhancing resonances at g=2.0017 and 2.0029 for C{sub 60} and C{sub 70} are observed; these are attributed to recombination of long-lived charged polarons. PLDMR of photooxidized and photopolymerized C60 and C70 reveals a third triplet exciton delocalized across several molecules. The PLDMR of a number of {pi}-conjugated polymer systems showed 3 features: a narrow PL-enhancing polaron resonance, broad full-, and half-field triplet exciton powder patterns. PLDMR on fullerene-doped polymers indicate that polarons and triplet excitons quench the PL and are stabilized by defects which break the conjugation. Results on conjugated polymers incorporating non-carbon atoms suggest that these sites trap both polarons and triplet excitons, increasing their lifetimes and populations. This and other results on electroluminescent devices implies that the energy levels of the polarons are distributed over a significant range.

• Research Organization: Ames Lab., IA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 50891
• Report Number(s): IS-T--1717; ON: DE95010131
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
40 CHEMISTRY
66 PHYSICS
COPOLYMERS
DOPED MATERIALS
EXCITONS
FULLERENES
MAGNETIC RESONANCE
PHOTOLUMINESCENCE
POLARONS
POLYMERS
TRIPLETS