Direct determination of trap density function based on the photoinduced charge carrier extraction technique

Hiroyuki Tajima, Tomohiko Suzuki, Motoi Kimata

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Photoinduced charge carrier extraction experiments using a linearly increasing voltage (photo-CELIV) are reported for an organic thin film device from 1.8 to 150 K. This device is composed of an active layer of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Photo-CELIV data for a zigzag shape voltage sweep provide critical evidence that the CELIV signal reflects the evacuation of charged carriers captured by traps under a high electric field. The data are analyzed using the Poole-Frenkel model. The trap density as a function of escape energy is obtained as ρ()=Dexp{-(-0)2/σ2}, with D = 1.0 × 1024 states m-3 eV-1, 0=0.087eV, and σ=0.029eV. The carrier drift mobility is estimated to be 2.3 × 10-6 cm2 V-1 s -1 at 1.8 K. As inferred from the light intensity dependence of the photo-CELIV data, geminate pairs are proposed as the origin of traps. This study demonstrates that carrier evacuation from a Coulomb potential effectively plays an important role in the electrical conduction of organic thin films.

Original languageEnglish
Pages (from-to)2272-2280
Number of pages9
JournalOrganic Electronics
Volume13
Issue number11
DOIs
Publication statusPublished - 2012 Nov
Externally publishedYes

Keywords

  • CELIV
  • Geminate pair
  • Photovoltaic effect
  • Solar cell
  • Trap

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering

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