TU Darmstadt / ULB / TUbiblio

Trap concentration dependence of thermally stimulated currents in small molecule organic materials

Weise, Wieland and Keith, Torsten and Malm, Norwin von and Seggern, Heinz von (2005):
Trap concentration dependence of thermally stimulated currents in small molecule organic materials.
In: Physical Review B, 72 (4), American Physical Society, pp. 045202-1, ISSN 1098-0121,
[Online-Edition: http://dx.doi.org/10.1103/physRevB.72.045202],
[Article]

Abstract

The effect of doping of thin organic glassy films of the hole transport material N,N′-di(1-naphthyl)N,N′-diphenylbenzidine (α-NPD) with various concentrations of 4,4′, 4″-tris(N-(1-naphthyl)-N-phenylamino)-triphenylamine (1-NaphDATA) is investigated with respect to the resulting charge carrier mobility and the effect on thermally stimulated currents (TSC). The energetic trap structure is obtained utilizing the fractional TSC technique. At low doping concentrations of a few percent the activation energy of an about 0.5 eV deep trap level is measured, which is related to the higher lying highest occupied molecular orbital level of 1-NaphDATA compared to the α-NPD matrix. A strong shift of the TSC peak towards higher temperatures with increasing dopant concentration is observed. It can be attributed to re-trapping despite the low film thickness of 200 nm. Thereby the effect of re-trapping is theoretically investigated and found to be composed of a mobility change and a change of the trap depth, as it is measured in fractional TSC measurements. The latter is related to enhanced re-trapping into deeper traps. The maximal peak shift occurs at about 4 vol % of dopant concentration, corresponding to about 2.7% molecular concentration. For higher concentrations of 1-NaphDATA the mobility increases again, and the TSC peak gradually changes to that of pure 1-NaphDATA, explainable by a progressive change from a deep-trap-controlled transport to a percolating transport on the 1-NaphDATA molecules.

Item Type: Article
Erschienen: 2005
Creators: Weise, Wieland and Keith, Torsten and Malm, Norwin von and Seggern, Heinz von
Title: Trap concentration dependence of thermally stimulated currents in small molecule organic materials
Language: English
Abstract:

The effect of doping of thin organic glassy films of the hole transport material N,N′-di(1-naphthyl)N,N′-diphenylbenzidine (α-NPD) with various concentrations of 4,4′, 4″-tris(N-(1-naphthyl)-N-phenylamino)-triphenylamine (1-NaphDATA) is investigated with respect to the resulting charge carrier mobility and the effect on thermally stimulated currents (TSC). The energetic trap structure is obtained utilizing the fractional TSC technique. At low doping concentrations of a few percent the activation energy of an about 0.5 eV deep trap level is measured, which is related to the higher lying highest occupied molecular orbital level of 1-NaphDATA compared to the α-NPD matrix. A strong shift of the TSC peak towards higher temperatures with increasing dopant concentration is observed. It can be attributed to re-trapping despite the low film thickness of 200 nm. Thereby the effect of re-trapping is theoretically investigated and found to be composed of a mobility change and a change of the trap depth, as it is measured in fractional TSC measurements. The latter is related to enhanced re-trapping into deeper traps. The maximal peak shift occurs at about 4 vol % of dopant concentration, corresponding to about 2.7% molecular concentration. For higher concentrations of 1-NaphDATA the mobility increases again, and the TSC peak gradually changes to that of pure 1-NaphDATA, explainable by a progressive change from a deep-trap-controlled transport to a percolating transport on the 1-NaphDATA molecules.

Journal or Publication Title: Physical Review B
Volume: 72
Number: 4
Publisher: American Physical Society
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Electronic Materials
Zentrale Einrichtungen
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue > D - Component properties
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue > D - Component properties > Subproject D4: Fatigue of organic electronic devices
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres
DFG-Collaborative Research Centres (incl. Transregio)
Date Deposited: 16 Sep 2011 14:00
Official URL: http://dx.doi.org/10.1103/physRevB.72.045202
Additional Information:

SFB 595 D4

Identification Number: doi:10.1103/physRevB.72.045202
Export:
Suche nach Titel in: TUfind oder in Google
Send an inquiry Send an inquiry

Options (only for editors)

View Item View Item