Electronic structure evolution and energy level alignment at C{sub 60}/4,4′-cyclohexylidenebis[N,N-bis(4-methylphenyl) benzenamine]/MoO{sub x}/indium tin oxide interfaces

Journal Article · Mon Apr 28 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4873959· OSTI ID:22273489

Liu, Xiaoliang ^[1]; Yi, Shijuan ^[1]; Wang, Chenggong; Wang, Congcong; Gao, Yongli ^[2]

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1. Hunan Key Laboratory for Super-microstructure and Ultrafast Process, College of Physics and Electronics, Central South University, Changsha 410083 (China)
2. Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States)

The electronic structure evolution and energy level alignment have been investigated at interfaces comprising fullerene (C{sub 60})/4,4′-cyclohexylidenebis[N,N-bis(4-methylphenyl) benzenamine] (TAPC)/ molybdenum oxide (MoO{sub x})/ indium tin oxide with ultraviolet photoemission spectroscopy and inverse photoemission spectroscopy. With deposition of TAPC upon MoO{sub x}, a dipole of 1.58 eV was formed at the TAPC/MoO{sub x} interface due to electron transfer from TAPC to MoO{sub x}. The highest occupied molecular orbital (HOMO) onset of TAPC was pinned closed to the Fermi level, leading to a p-doped region and thus increasing the carrier concentration at the very interface. The downward band bending and the resulting built-in field in TAPC were favorable for the hole transfer toward the TAPC/MoO{sub x} interface. The rigid downward shift of energy levels of TAPC indicated no significant interface chemistry at the interface. With subsequent deposition of C{sub 60} on TAPC, a dipole of 0.27 eV was observed at the C{sub 60}/TAPC heterojunction due to the electron transfer from TAPC to C{sub 60}. This led to a drop of the HOMO of TAPC near the C{sub 60}/TAPC interface, and hence further enhanced the band bending in TAPC. The band bending behavior was also observed in C{sub 60}, similarly creating a built-in field in C{sub 60} film and improving the electron transfer away from the C{sub 60}/TAPC interface. It can be deduced from the interface analysis that a promising maximum open circuit voltage of 1.5 eV is achievable in C{sub 60}/TAPC-based organic photovoltaic cells.

• OSTI ID: 22273489
• Journal Information: Journal of Applied Physics, Vol. 115, Issue 16; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CONCENTRATION RATIO
DIPOLES
ELECTRON TRANSFER
ELECTRONIC STRUCTURE
EMISSION SPECTROSCOPY
FERMI LEVEL
FULLERENES
HETEROJUNCTIONS
HOLES
INDIUM COMPOUNDS
INTERFACES
MOLECULAR ORBITAL METHOD
MOLYBDENUM OXIDES
PHOTOEMISSION
PHOTOVOLTAIC CELLS
THIN FILMS
TIN OXIDES
ULTRAVIOLET RADIATION