Mechanistic description of the efficiency loss in organic phosphorescent host–guest systems due to triplet-polaron quenching

Arnout Ligthart, Teun D.G. Nevels, Christ H.L. Weijtens, Peter A. Bobbert, Reinder Coehoorn (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

In this study we demonstrate how a mechanistic description can be obtained of the interplay of all processes that give rise to the efficiency loss due to triplet polaron quenching (TPQ) in phosphorescent host-guest systems such as used in organic light-emitting diodes (OLEDs). We study unipolar devices with an emissive layer consisting of m-MTDATA:Ir(ppy)2(acac), in which excitons on the phosphorescent Ir(ppy)2(acac) molecules are quenched by holes on the m-MTDATA host. The final TPQ-process is disentangled from all other relevant processes, such as polaron and exciton diffusion and field-induced exciton dissociation, by carrying out a combination of electrical, photoluminescence (PL) and field-induced dissociation experiments. The analysis is supported by carrying out kinetic Monte Carlo simulations. We find that a conventional approach, within which the loss is phenomenologically quantified using a rate coefficient, cannot consistently describe all experimental results. For a wide temperature range a fair mechanistic description of all results is obtained when using a TPQ Förster radius of 3.8 nm and a triplet exciton binding energy of 0.9 eV.

Original languageEnglish
Article number106058
Number of pages10
JournalOrganic Electronics
Volume91
DOIs
Publication statusPublished - Apr 2021

Keywords

  • Field-induced dissociation
  • Kinetic Monte Carlo simulations
  • Organic light-emitting diodes
  • Organic semiconductors
  • Roll-off
  • Triplet-polaron quenching

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