Understanding the Origin of the 535 nm Emission Band in Oxidized Poly(9,9-dioctylfluorene): The Essential Role of Inter-Chain/Inter-Segment Interactions

Autor: Marc Sims, M. Koeberg, Donal D. C. Bradley, Aristidis Asimakis, Martin Grell, David G. Lidzey, M. Ariu
Rok vydání: 2004
Předmět:
Zdroj: Advanced Functional Materials. 14:765-781
ISSN: 1616-3028
1616-301X
DOI: 10.1002/adfm.200305149
Popis: We present a careful study of the effects of photo-oxidation on the emissive properties of poly(9,9-dioctylfluorene) (PFO) that addresses important issues raised by a recent flurry of publications concerning the degradation of blue light-emitting, fluorene-based homo- and copolymers. The photoluminescence (PL) spectra of thin PFO films oxidized at room temperature comprise two major components, namely a vibronically structured blue band and a green, structureless component, referred to hereafter as the ‘g-band’. These are common features in a wide range of poly(fluorene)s (PFs) and whilst the former is uniformly accepted to be the result of intra-chain, fluorene-based, singlet-exciton emission, the origin of the ‘g-band’ is subject to increasing debate. Our studies, described in detail below, support the proposed formation of oxidation-induced fluorenone defects that quench intra-chain, singlet-exciton emission and activate the g-band emission. However, whilst these fluorenone defects are concluded to be necessary for the g-band emission to be observed, they are considered not to be, alone, sufficient. We show that inter-chain/inter-segment interactions are required for the appearance of the g-band in the PL spectra of PFO and propose that the g-band is attributable to emission from fluorenone-based excimers rather than from localized fluorenone π–π* transitions as recently suggested.
Databáze: OpenAIRE
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