Universal Strategy for Efficient Electron Injection into Organic Semiconductors Utilizing Hydrogen Bonds

Abstract

Molecular n-dopants that can lower the electron injection barrier between organic semiconductors and electrodes are essential in present-day organic electronics. However, the development of stable molecular n-dopants remains difficult owing to their low ionization potential, which generally renders them unstable. It is shown that the stable bases widely used in organic synthesis as catalysts can lower the electron injection barrier similar to that in conventional n-doping in organic optoelectronic devices. In contrast to conventional n-doping, which is based on the electron transfer from dopants with low ionization potential, the reduction of the injection barrier caused by adding bases is determined by the formation of hydrogen bonds between the hosts and the bases, providing energy-level-independent electron injection. The observation of the efficient electron injection induced by hydrogen bonding affords new perspectives on the method for controlling the behavior of electrons unique to organic semiconductors.