A research group from the National Institute of Advanced Industrial Science and Technology (AIST) and the University of Tsukuba found that coating the electrodes of an organic semiconductor device with caffeic acid, a component found in coffee, increases the current flowing through the device by up to 100 times. I discovered.
In order to increase the current flowing through an organic semiconductor device and improve the performance of the device, it is important to improve the efficiency of charge injection from the electrode to the semiconductor.The researchers focused on phenylpropanoids as molecules with a large permanent dipole moment because modification of the electrode surface with molecules with a large permanent dipole moment can promote charge injection from the electrode to the semiconductor.
Phenylpropanoids are substances produced by plants and exhibit the property of adsorbing to metals.Among them, "caffeic acid", which is contained in coffee and has a large permanent dipole moment, was used, and a thin film layer of caffeic acid was formed on the electrode surface of an organic semiconductor device and observed.As a result, the caffeic acid molecules spontaneously aligned on the electrode surface, and the current flowing through the organic semiconductor device increased up to 100 times compared to the case without caffeic acid.The catechol group of caffeic acid easily binds to the solid surface and preferentially adsorbs to the electrode surface. As a result, the caffeic acid exhibits a specific orientation, which changes the potential of the electrode surface and promotes charge injection into the semiconductor. The research group believes that
The effect of the thin film layer of caffeic acid is confirmed even when the type of electrode is changed to gold, silver, copper, iron, silicon, etc., and functions as a versatile electrode modification layer.Conductive polymers and transition metal oxides are known as electrode modification layers that have been conventionally used to facilitate the flow of electric charge, but the environmental load at the time of disposal has been viewed as a problem.The present discovery that caffeic acid, which can be obtained from plants, can improve the performance of electrodes, is expected to be a step toward the realization of biomass-derived organic semiconductor devices with low environmental impact.
Paper information:[Advanced Materials Interfaces] Increasing Electrode Work Function Using a Natural Molecule
