Enhancement of hole injection and electroluminescence characteristics by a rubbing-induced lying orientation of alpha-sexithiophene

Toshinori Matsushima, Hideyuki Murata

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The authors find that rubbing a film of alpha-sexithiophene (α-6T) with a nylon cloth induces a change from standing to lying orientations in a film surface region. While current densities of hole-only devices based on 4,4′,4″-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (m-MTDATA) are independent of the rubbing number of α-6T, current densities of hole-only devices based on N-N′-diphenyl-N-N′-bis(1- naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) and 4,4′-bis(carbazol-9-yl)-2,2′-biphenyl (CBP) markedly increase (≈42 times at 1 V for the α-NPD devices and ≈236 times at 1 V for the CBP devices) as the rubbing number of α-6T is increased. The increase in current density is ascribed to enhanced hole injection through a -5.28 eV energy level of lying α-6T domains instead of a -4.95 eV energy level of standing α-6T domains and improved overlaps between an electronic cloud of indium tin oxide, π orbitals of lying α-6T molecules, and π orbitals of molecules of α-NPD and CBP at heterojunction interfaces. The rubbing of α-6T is also demonstrated to reduce drive voltages (by ≈40 at 10 mA/cm 2) and increase power conversion efficiency (by ≈26 at 10 mA/cm 2) of organic light-emitting diodes. Finally, half lifetimes are significantly enhanced (4.3 times) at a current density of 50 mA/cm 2.

Original languageEnglish
Article number024503
JournalJournal of Applied Physics
Volume112
Issue number2
DOIs
Publication statusPublished - Jul 15 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Fingerprint Dive into the research topics of 'Enhancement of hole injection and electroluminescence characteristics by a rubbing-induced lying orientation of alpha-sexithiophene'. Together they form a unique fingerprint.

  • Cite this