TY - JOUR
T1 - Correlation between energy level alignment and device performance in planar heterojunction organic photovoltaics
AU - Akaike, Kouki
AU - Kubozono, Yoshihiro
N1 - Funding Information:
This work was supported partly by Grants-in-Aids 22244045 and 22850012 from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), the special budget for solar cells of Okayama prefecture, and the Okayama University COE project.
PY - 2013/1
Y1 - 2013/1
N2 - 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.
AB - 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.
KW - Donor/acceptor interface
KW - Energy level alignment
KW - Interfacial electronic structure
KW - Kelvin probe method
KW - Organic photovoltaics
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U2 - 10.1016/j.orgel.2012.09.025
DO - 10.1016/j.orgel.2012.09.025
M3 - Article
AN - SCOPUS:84869875078
SN - 1566-1199
VL - 14
SP - 1
EP - 7
JO - Organic Electronics
JF - Organic Electronics
IS - 1
ER -