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Trap Generation Dynamics in Photo-Oxidised DEH Doped Polymers

Division of Physics, University of Dundee, Perth Road, Dundee DD1 4HN, UK
Academic Editor: Alessandro Lavacchi
Coatings 2015, 5(3), 263-277;
Received: 27 May 2015 / Revised: 23 June 2015 / Accepted: 29 June 2015 / Published: 3 July 2015
(This article belongs to the Special Issue Trends in Coatings and Surface Technology—Feature Papers)
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A series of polyester films doped with a hole transport molecule, p-diethylaminobenzaldehyde-1,1'-diphenylhydrazone (DEH), have been systematically exposed to ultraviolet radiation with a peak wavelength of about 375 nm. The electronic performance of the films, evaluated using time-of-flight and space-charge current injection methods, is observed to continuously degrade with increasing ultraviolet exposure. The degradation is attributed to photo cyclic oxidation of DEH that results in the creation of indazole (IND) molecules which function as bulk hole traps. A proposed model for the generation dynamics of the IND traps is capable of describing both the reduction in current injection and the associated time-of-flight hole mobility provided around 1% of the DEH population produce highly reactive photo-excited states which are completely converted to indazole during the UV exposure period. The rapid reaction of these states is incompatible with bulk oxygen diffusion-reaction kinetics within the films and is attributed to the creation of excited states within the reaction radius of soluble oxygen. It is suggested that encapsulation strategies to preserve the electronic integrity of the films should accordingly focus upon limiting the critical supply of oxygen for photo cyclic reaction. View Full-Text
Keywords: DEH; photo-oxidation; indazole; traps DEH; photo-oxidation; indazole; traps

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Goldie, D.M. Trap Generation Dynamics in Photo-Oxidised DEH Doped Polymers. Coatings 2015, 5, 263-277.

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