Transient electroluminescence under short and strong voltage pulses

Haim Chayet; Roman Pogreb; Dan Davidov

doi:10.1117/12.279338

1 December 1997 Transient electroluminescence under short and strong voltage pulses

Haim Chayet, Roman Pogreb, Dan Davidov

Proceedings Volume 3148, Organic Light-Emitting Materials and Devices; (1997) https://doi.org/10.1117/12.279338
Event: Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United States

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.

Citation Download Citation

Haim Chayet, Roman Pogreb, and Dan Davidov "Transient electroluminescence under short and strong voltage pulses", Proc. SPIE 3148, Organic Light-Emitting Materials and Devices, (1 December 1997); https://doi.org/10.1117/12.279338

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