Correlation between energy level alignment and device performance in planar heterojunction organic photovoltaics

Kouki Akaike, Yoshihiro Kubozono

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


Information on the interfacial electronic structure in organic photovoltaics (OPVs) is essential for fully understanding features of device operation such as the photocurrent generation and relative energy band offsets at the donor/acceptor interface, which directly affect the open circuit voltage (Voc). Kelvin probe (KP) measurements fully reveal the energy level alignment in a prototype OPV with a copper phthalocyanine (CuPc)/fullerene (C60) planar heterojunction. Energy level pinning at the CuPc/C 60 junction fixes the energy band offsets of C60. A downward energy shift of about 0.9 eV appears at the C60/ bathocuproine junction, which may act as a hole-blocking barrier. A combination of KP and current density-voltage measurements indicates that photocurrent generation depends strongly on the magnitude of the upward energy shift at the CuPc/C60 junction. The dependence of Voc on the substrate work function is also discussed in terms of the energy level alignment at indium tin oxide/CuPc/C60 junctions.

Original languageEnglish
Pages (from-to)1-7
Number of pages7
JournalOrganic Electronics
Issue number1
Publication statusPublished - Jan 2013


  • Donor/acceptor interface
  • Energy level alignment
  • Interfacial electronic structure
  • Kelvin probe method
  • Organic photovoltaics

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering


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