TITLE:
Impedance Spectroscopy for Annealing-Induced Change of Molybdenum Oxide in Organic Photovoltaic Cell
AUTHORS:
Toshifumi Kobori, Norihiko Kamata, Takeshi Fukuda
KEYWORDS:
Organic Photovoltaic Cells, PTB7-Th, MoOx, Annealing, Impedance Spectroscopy
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.7 No.8,
July
28,
2017
ABSTRACT: Organic photovoltaic cells (OPVs) have been
investigated for a long time, and practical realizations have been also in
progress due to their high photovoltaic performance over 12%. In this study, we
fabricated normal OPVs and investigated the reason of an improved
optical-to-electrical conversion efficiency by annealing the MoOx layer. The photoconversion efficiency was improved up to 5.65% from 2.05% after
annealing at 160°C for 5 min, and the external quantum efficiency also
increased for all the measurement wavelength ranging from 300 to 900 nm. Especially, the short circuit
current density increased among photovoltaic parameters. The carrier transport
resistance of photoactive layer was found to be reduced by evaluating the
impedance measurement. These results indicate that defects at the MoOx/organic
interface were successfully reduced by the thermal annealing process of MoOx layer. The efficient carrier transport was realized for the annealed-device,
resulting in the high device performance. In addition, the relaxation and
electron recombination times were also reduced by the annealing process, which
lead to the improved photovoltaic performance.