Masahiro Morimoto

Assistant Professor, Academic Assembly Faculty of Engineering, University of Toyama *Profile is at the time of the award.

2021Inamori Research GrantsBiology & Life sciences

Research topics
Polarization and Carrier Transfer Characteristics at Metal/Organic Semiconductor Interface
The charge transfer and injection mechanisms at the metal/organic semiconductor interface have been investigated, but almost studies have explained existing material systems, and the transfer and injection of holes and electrons have been discussed separately. In this study, I aim to elucidate the correlation between the physical chemical structure of the molecular polarization and the electronic properties such as hole and electron transfer and injection. I try improving the charge transfer between metal and semiconductor by controlled molecular dipoles on the metal electrode surface.


I think it is interesting to try to control the "conductivity" at the metal/semiconductor interface with an "insulator" called a molecular dipole.

Outline of Research Achievments

An efficient carrier injection at the electrode/organic semiconductor interface of organic light-emitting diodes (OLEDs) is challenging. It is well-known that an electric dipole at the electrode/semiconductor interface improves the carrier injection from the electrode because of a vacuum-level shift. In this study, poly (vinylidene fluoride-trifluoroethylene) [P(VDF/TrFE)] is used as a polar polymer with spontaneous polarization. P(VDF/TrFE) is spin-coated on an indium tin oxide (ITO) electrode surface as a hole injection layer for OLEDs. The P(VDF/TrFE) layer enhances the hole injection from the ITO electrode by causing a vacuum-level shift. As a result, the device driving voltage can be lowered. In addition, annealing temperature dependence is observed. To investigate the origin of the hole injection effect, the P(VDF/TrFE)-layered ITO surface and the thin film structure of the P(VDF/TrFE) layer are measured. The P(VDF/TrFE) layers at different annealing temperatures show no difference in surface properties but show significant differences in the thin film structure. The hole injection of OLEDs is significantly enhanced because of the structural change in ultrathin P(VDF/TrFE) layer.

Fukazawa, R., Maegawa, Y., Morimoto, M., Matsubara, R., Kubono, A. and Naka, S. (2023), Hole Injection Characteristics and Annealing Temperature Dependence for Organic Light-Emitting Diodes Using Spontaneous Polarization. Phys. Status Solidi A, 220: 2300161.

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Biology & Life sciences