TY - JOUR
T1 - Large bipolaron density at organic semiconductor/electrode interfaces
AU - Dhanker, Rijul
AU - Gray, Christopher L.
AU - Mukhopadhyay, Sukrit
AU - Nunez, Sean
AU - Cheng, Chiao Yu
AU - Sokolov, Anatoliy N.
AU - Giebink, Noel C.
N1 - Funding Information:
This work was supported in part by the Dow Chemical Company as part of the Flexible Electronics UPI program and by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DE-SC0012365.
Publisher Copyright:
© 2017 The Author(s).
PY - 2017/12/1
Y1 - 2017/12/1
N2 - 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.
AB - 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.
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U2 - 10.1038/s41467-017-02459-3
DO - 10.1038/s41467-017-02459-3
M3 - Article
C2 - 29269880
AN - SCOPUS:85042362401
VL - 8
JO - Nature Communications
JF - Nature Communications
SN - 2041-1723
IS - 1
M1 - 2252
ER -