Laser-induced degradation studies of photoluminescence of PPV and CNPPV thin films

Degradation of active polymer materials in presence of light, oxygen and moisture is known to be the most important reason limiting the lifetime of devices fabricated using light-emitting polymers. We focus on the monitoring of degradation of the two most popular light-emitting polymers PPV and CNPP...

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Bibliographic Details
Published in:Thin solid films 2005-04, Vol.477 (1), p.162-168
Main Authors: Ghosh, D., Samal, G.S., Biswas, A.K., Mohapatra, Y.N.
Format: Article
Language:English
Subjects:
CNPPV
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
Laser degradation
Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation
Photodegradation
Photoluminescence
Photooxidation
Physical radiation effects, radiation damage
Physics
PL enhancement
PPV
Solid organic materials
Structure of solids and liquids
crystallography
Ultraviolet, visible, and infrared radiation effects (including laser radiation)
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Summary:Degradation of active polymer materials in presence of light, oxygen and moisture is known to be the most important reason limiting the lifetime of devices fabricated using light-emitting polymers. We focus on the monitoring of degradation of the two most popular light-emitting polymers PPV and CNPPV. We develop a procedure for accelerated laser-induced degradation and quantify degradation rate by monitoring loss of photoluminescence (PL) with irradiation time. We use this procedure to optimise thin film preparation conditions in terms of ambient and heat treatment schedule. Laser irradiation of PPV in air shows second-order exponential decay of PL intensity along with blue shift, while the decay is first order for CNPPV with no significant blue shift. Similar experiments with laser irradiation for vacuum-dried PPV films show PL enhancement under vacuum with slower subsequent degradation in air, demonstrating efficacy of vacuum drying in reducing oxygen content of processed films. No PL peak shift is observed with laser irradiation under vacuum, clearly indicating absence of contribution from chains of reduced conjugation length. In addition to PL enhancement, significant resistance to photodegradation is observed on laser irradiation in vacuum.
ISSN:0040-6090
1879-2731
DOI:10.1016/j.tsf.2004.08.126