Unmasking Electronic Energy Transfer of Conjugated Polymers by Suppression of O 2 Quenching

• Published in: Science (American Association for the Advancement of Science) Vol. 289; no. 5483; pp. 1327 - 1330
• Main Authors: Yu, Ji, Hu, Dehong, Barbara, Paul F.
• Format: Journal Article
• Language: English
• Published: 25.08.2000
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.289.5483.1327

The photochemistry of poly[2-methoxy, 5-(2′-ethyl-hexyloxy)- p -phenylene-vinylene] (MEH-PPV) has been found to be highly dependent on the presence of O 2 , which increases singlet exciton quenching dramatically. Spectroscopy on isolated single molecules of MEH-PPV in polycarbonate films that exclude O 2 reveals two distinct polymer conformations with fluorescence maxima near 555 and 580 nanometers wavelength, respectively. Time-resolved single-molecule data demonstrate that the 580-nanometer conformation exhibits a “landscape” for intramolecular electronic energy relaxation with a “funnel” that contains a 580-nanometer singlet exciton trap at the bottom. The exciton traps can be converted to exciton quenchers by reaction with O 2 . Conformationally induced, directed-energy transfer is arguably a critical dynamical process that is responsible for many of the distinctive photophysical properties of conjugated polymers.