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Quantitative Fermi level tuning in amorphous organic semiconductor by molecular doping: Toward full understanding of the doping mechanism.
- Source :
-
Applied Physics Letters . 9/5/2016, Vol. 109 Issue 9, p093302-1-093302-5. 5p. 4 Graphs. - Publication Year :
- 2016
-
Abstract
- The doping mechanism in organic-semiconductor films has been quantitatively studied via ultrahigh-sensitivity ultraviolet photoelectron spectroscopy of N,N-bis(1-naphthyl)-N,N-diphenyl-1,1-biphenyl-4,4-diamine (α-NPD) films doped with hexaazatriphenylene-hexacarbonitrile [HAT(CN)6]. We observed that HOMO of α-NPD shifts to the Fermi level (EF) in two different rates with the doping concentration of HAT(CN)6, but HOMO distributions of both pristine and doped amorphous α-NPD films are excellently approximated with a same Gaussian distribution without exponential tail states over ∼5 × 1018 cm-3 eV-1. From the theoretical simulation of the HAT(CN)6-concentration dependence of the HOMO in doped films, we show that the passivation of Gaussian-distributed hole traps, which peak at 1.1 eV above the HOMO onset, occurs at ultralow doping [HAT(CN)6 molecular ratio (MR) < 0.01], leading to a strong HOMO shift of ∼0.40 eV towards EF, and MR dependence of HOMO changes abruptly at MR∼0.01 to a weaker dependence for MR>0.01 due to future of the dopant acceptor level. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00036951
- Volume :
- 109
- Issue :
- 9
- Database :
- Academic Search Index
- Journal :
- Applied Physics Letters
- Publication Type :
- Academic Journal
- Accession number :
- 117844940
- Full Text :
- https://doi.org/10.1063/1.4962052