Transient electroluminescence under short and strong voltage pulses

Haim Chayet, Roman Pogreb, Dan Davidov

Research output: Contribution to journalConference articlepeer-review

4 Scopus citations


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 (centered at 390 nm, ≈3.17 eV); 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 pulses. 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.

Original languageEnglish
Pages (from-to)34-44
Number of pages11
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 1997
Externally publishedYes
EventOrganic Light-Emitting Materials and Devices - San Diego, CA, United States
Duration: 30 Jul 19971 Aug 1997


  • Conjugated polymers
  • Electroluminescence
  • Exciton
  • High-voltage pulses
  • Light-emitting diode
  • PPV
  • UV emission


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