Higher order effects in organic LEDs with sub-bandgap turn-on

Sebastian Engmann, Adam J. Barito, Emily G. Bittle, Noel C. Giebink, Lee J. Richter, David J. Gundlach

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


Spin-dependent nonlinear processes in organic materials such as singlet-fission and triplet-triplet annihilation could increase the performance for photovoltaics, detectors, and light emitting diodes. Rubrene/C 60 light emitting diodes exhibit a distinct low voltage (half-bandgap) threshold for emission. Two origins for the low voltage turn-on have been proposed: (i) Auger assisted energy up-conversion, and (ii) triplet-triplet annihilation. We test these proposals by systematically altering the rubrene/C 60 interface kinetics by introducing thin interlayers. Quantitative analysis of the unmodified rubrene/C 60 device suggests that higher order processes can be ruled out as the origin of the sub-bandgap turn-on. Rather, band-to-band recombination is the most likely radiative recombination process. However, insertion of a bathocuproine layer yields a 3-fold increase in luminance compared to the unmodified device. This indicates that suppression of parasitic interface processes by judicious modification of the interface allows a triplet-triplet annihilation channel to be observed.

Original languageEnglish (US)
Article number227
JournalNature communications
Issue number1
StatePublished - Dec 1 2019

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Biochemistry, Genetics and Molecular Biology
  • General Physics and Astronomy


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