Interface control of organic devices by using self-assembled monolayers

Interface between inorganic electrode and organic layer bears various problems, such as poor adhesion strength and charge injection barrier due to inconsistency in physicochemical properties of both materials. This paper reviews the experimental results of using self-assembled monolayers (SAMs) that have reactive terminal groups to resolve the problems of organic/inorganic interface. Polymer thin films that are covalently tethered to inorganic surfaces can be prepared by vapor-depositing monomer molecules on the substrates that were modified with SAMs having a function of polymerization initiator. The reactive units can be amino group for ring-opening polymerization, azo group for UV-assisted vinyl polymerization, and benzophenone unit for thermally-assisted vinyl polymerization. A polymer thin film prepared by spin-coating can also be tethered via a benzophenone-terminated SAM by photochemical reaction. The chemical tethering at the interface resulted in increase of adhesion strength, improvement of surface morphology, and increase of charge injection from the inorganic substrates. © 2015 The Institute of Electrical Engineers of Japan.