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Proceedings Paper

Luminescence of thin films of conjugated rigid-rod polymer PBT
Author(s): Li-Wei Tu; K. H. Lee; Chih-Ming Lai; S. J. Bai; C. C. Wu
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Paper Abstract

Heterocyclic aromatic polymer poly(p- phenylenebenzobisthiazole), PBT, is a rigid-rod polymer having a fully conjugated backbone as well as excellent dimensional, thermo-oxidative, and solvent stabilities. A PBT polymer with intrinsic viscosity of 18.0 dL/g was dissolved in methanesulfonic acid or Lewis acid. The PBT solution was spin- coated, doctor-bladed or extruded for freestanding films or onto an indium-tin-oxide (ITO) substrate. The acid was removed via coagulation resulted in PBT films of about 80 nm in thickness on the ITO substrate as determined by scanning electron microscopy. X-ray scattering demonstrated that the extruded freestanding films were uniaxial while the others were isotropic without long-range order. Both temperature and excitation power dependences of the photoluminescence measurements were performed. The laser excitation power dependence of the emission intensity is fitted well with a bimolecular recombination model. Light-emitting devices were fabricated with a structure of Al(Mg)/PBT/ITO/glass, and gave out green-yellow light. A threshold voltage as low as 1 V was achieved. Electroluminescence spectra showed a blue-shift with increasing voltage, which is ascribed to the band-filling effect. Vibrational structure emerged in the photoluminescence spectra at low temperatures, and was observed in the electroluminescence spectra at high voltages, which gives a vibrational mode spacing of 186 meV for the lowest levels.

Paper Details

Date Published: 14 May 2001
PDF: 9 pages
Proc. SPIE 4278, Light-Emitting Diodes: Research, Manufacturing, and Applications V, (14 May 2001); doi: 10.1117/12.426849
Show Author Affiliations
Li-Wei Tu, National Sun Yat-Sen Univ. (Taiwan)
K. H. Lee, National Sun Yat-Sen Univ. (Taiwan)
Chih-Ming Lai, National Sun Yat-Sen Univ. (Taiwan)
S. J. Bai, National Sun Yat-Sen Univ. (Taiwan)
C. C. Wu, National Sun Yat-Sen Univ. (Taiwan)

Published in SPIE Proceedings Vol. 4278:
Light-Emitting Diodes: Research, Manufacturing, and Applications V
H. Walter Yao; E. Fred Schubert, Editor(s)

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