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Proceedings Paper

Transient electroluminescence under short and strong voltage pulses
Author(s): Haim Chayet; Roman Pogreb; Dan Davidov
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Paper Abstract

We present high voltage pulsed electroluminescence (EL) measurements on light-emitting diodes (LED) based on thin films of poly(p-phenylenevinylene) (PPV) sandwiched between Indium-Tin-Oxide (ITO) and Aluminum electrodes. We observe two regimes in the LED operation depending on the driving pulsed current density. At low current densities, below 50A/cm2, the pulsed EL follows its DC characteristics with yellow-green emission. Above some threshold current density we observe additional UV-violet emission; the amplitude of the pulsed UV EL increases exponentially with the applied voltage. When the amplitude of the voltage pulses is around 300 V, the current signal exhibits a sharp current peak followed by a dramatic increase in UV EL intensity but only moderate increase of the green emission. We propose a possible explanation for the appearance of the UV emission upon application of strong electrical pulse. It is due, we believe, to 'hot' carriers in strong fields which partially inhibit the formation of singlet excitons and enhance the probability for direct inter-band radiative transitions. We show that our very simple device can be operated at current density as high as 140 A/cm2 and achieve a peak brightness of 105 cd/m2 without appreciable degradation.

Paper Details

Date Published: 1 December 1997
PDF: 11 pages
Proc. SPIE 3148, Organic Light-Emitting Materials and Devices, (1 December 1997); doi: 10.1117/12.279338
Show Author Affiliations
Haim Chayet, Hebrew Univ. of Jerusalem (Israel)
Roman Pogreb, Hebrew Univ. of Jerusalem and College of Judea and Samaria (Israel)
Dan Davidov, Hebrew Univ. of Jerusalem (Israel)

Published in SPIE Proceedings Vol. 3148:
Organic Light-Emitting Materials and Devices
Zakya H. Kafafi, Editor(s)

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