Direct Measurement of the Triplet Exciton Diffusion Length in Organic Semiconductors

Oleksandr V. Mikhnenko*, Roald Ruiter, Paul W. M. Blom, Maria Antonietta Loi

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

We present a new method to measure the triplet exciton diffusion length in organic semiconductors. N,N'-di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine (NPD) has been used as a model system. Triplet excitons are injected into a thin film of NPD by a phosphorescent thin film, which is optically excited and forms a sharp interface with the NPD layer. The penetration profile of the triplet excitons density is recorded by measuring the emission intensity of another phosphorescent material (detector), which is doped into the NPD film at variable distances from the injecting interface. From the obtained triplet penetration profile we extracted a triplet exciton diffusion length of 87 +/- 2.7 nm. For excitation power densities >1 mW/mm(2) triplet-triplet annihilation processes can significantly limit the triplet penetration depth into organic semiconductor. The proposed sample structure can be further used to study excitonic spin degree of freedom.

Original languageEnglish
Article number137401
Pages (from-to)137401-1-137401-5
Number of pages5
JournalPhysical Review Letters
Volume108
Issue number13
DOIs
Publication statusPublished - 29-Mar-2012

Keywords

  • LIGHT-EMITTING-DIODES
  • TRANSIENT ANALYSIS
  • THIN-FILM
  • SINGLET
  • ELECTROPHOSPHORESCENCE
  • FLUORESCENT
  • EFFICIENCY
  • PORPHYRIN
  • DYNAMICS
  • DEVICES

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