da Silva, S D C*; Foschini, M*; Silva, H S*; Tozoni, J R*; Castro, F A; Silva, R A*; Marletta, A* (2012) Molecular relaxation temperature effects on emission efficiency of organic light-emitting diodes. Organic Electron., 13 (12). pp. 2935-2939.

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Abstract

This paper reports the influence of the molecular relaxation temperature and electric field on the emission efficiency of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) in Organic Light-Emitting Diode (OLED) structure. We observe that the photoluminescence (PL) depends on the OLED polarization (forward and reverse) and on MEH-PPV molecular ß-relaxation (Tß ~ 220 K) and a-relaxation (Ta ~ 330 K) temperatures. Above Tß unbalance in charge carrier concentration in the device have a significant effect on the emission efficiency. The exciton energy transfer as a function of the sample temperature was determined using emission ellipsometry within the Stokes’ theory scope. Regardless of the OLED voltage polarization, the emission is partially linearly polarized and the polarization degree decreases significantly above Tß and Ta temperatures. Finally, we propose an approach to enhance the emission efficiency of luminescence polymers by controlling the molecular relaxation temperatures of the multilayer polymer OLEDs.

Item Type:	Article
Keywords:	OLED, photoluminescence, organic electronics
Subjects:	Advanced Materials Advanced Materials > Photovoltaics
Identification number/DOI:	10.1016/j.orgel.2012.07.046
Last Modified:	02 Feb 2018 13:14
URI:	http://eprintspublications.npl.co.uk/id/eprint/5675

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