Large bipolaron density at organic semiconductor/electrode interfaces
- Pennsylvania State Univ., University Park, PA (United States). Dept of Electrical Engineering
- Pennsylvania State Univ., University Park, PA (United States). Dept of Chemistry
- Dow Chemical Co., Midland, MI (United States)
- Pennsylvania State Univ., University Park, PA (United States). Dept of Materials Science
Bipolaron states, in which two electrons or two holes occupy a single molecule or conjugated polymer segment, are typically considered to be negligible in organic semiconductor devices due to Coulomb repulsion between the two charges. Here we use charge modulation spectroscopy to reveal a bipolaron sheet density >1010 cm–2 at the interface between an indium tin oxide anode and the common small molecule organic semiconductor N,N'-Bis(3-methylphenyl)-N,N'-diphenylbenzidine. We find that the magnetocurrent response of hole-only devices correlates closely with changes in the bipolaron concentration, supporting the bipolaron model of unipolar organic magnetoresistance and suggesting that it may be more of an interface than a bulk phenomenon. These results are understood on the basis of a quantitative interface energy level alignment model, which indicates that bipolarons are generally expected to be significant near contacts in the Fermi level pinning regime and thus may be more prevalent in organic electronic devices than previously thought.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
- Contributing Organization:
- Dow Chemical Company
- Grant/Contract Number:
- SC0012365
- OSTI ID:
- 1523500
- Journal Information:
- Nature Communications, Vol. 8, Issue 1; ISSN 2041-1723
- Publisher:
- Nature Publishing GroupCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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