Fundamental tradeoff between emission intensity and efficiency in light-emitting electrochemical cells

S. van Reenen, R.A.J. Janssen, M. Kemerink

Research output: Contribution to journalArticleAcademicpeer-review

46 Citations (Scopus)
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Abstract

The characteristic doping process in polymer light-emitting electrochemical cells (LECs) causes a tradeoff between luminescence intensity and efficiency. Experiments and numerical modeling on thin film polymer LECs show that, on the one hand, carrier injection and transport benefit from electrochemical doping, leading to increased electron-hole recombination. On the other hand, the radiative recombination efficiency is reduced by exciton quenching by polarons involved in the doping. Consequently, the quasi-steady-state luminescent efficiency decreases with increasing ion concentration. The transient of the luminescent efficiency shows a characteristic roll-off while the current continuously increases, attributed to ongoing electrochemical doping and the associated exciton quenching. Both effects can be modeled by exciton polaron-quenching via diffusion-assisted Förster resonance energy transfer. These results indicate that the tradeoff between efficiency and intensity is fundamental, suggesting that the application realm of future LECs should be sought in high-brightness, low-production cost devices, rather than in high-efficiency devices. A fundamental tradeoff between emission intensity and efficiency in light-emitting electrochemical cells is reported. The admixed ions in LECs on the one hand improve charge transport by electrochemical doping, but on the other hand reduce the luminescent efficiency by quenching of excitons for KCF3SO3 densities of >1025 m-3.

Original languageEnglish
Pages (from-to)3066-3073
Number of pages8
JournalAdvanced Functional Materials
Volume25
Issue number20
DOIs
Publication statusPublished - 27 May 2015

Keywords

  • charge transport
  • conjugated polymers
  • doping
  • organic light-emitting electrochemical cells
  • recombination

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