In this study, we systematically investigated the stoichiometric dependence of titanium oxide (TiOx, x=1.56-1.93) as a cathode modifier on the device performance of polymer solar cells. Electronic structures of the synthesized TiOx modifier layers were controlled by tuning the compositions of various O/Ti ratios. The effective cathode work-functions and the corresponding device performances of polymer solar cells are systematically changed as a result of inserting the TiOx modification layers. Interfacial modification of the Al cathode with a low O/Ti ratio of TiO x layer yields the best performing photovoltaic device as a result of a largest built-in potential. The correlation of power conversion efficiencies and carrier dynamics of these devices by inserting various TiOx modification layer is further examined by using the Mott-Schottky analysis and the impedance spectroscopy technique. The consistent result shows an enhanced carrier collection efficiency and a reduced charge recombination rate of the device via adequate band alignment between the photoactive layer and the cathode using the TiOx modification layer with an optimized O/Ti ratio.
ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films
Yeh, Y. C., Li, S. S., Wu, C. C., Shao, T. W., Kuo, P. C., & Chen, C. W. (2014). Stoichiometric dependence of TiOx as a cathode modifier on band alignment of polymer solar cells. Solar Energy Materials and Solar Cells, 125, 233-238. https://doi.org/10.1016/j.solmat.2014.03.017