The effects of polyethylenimine-ethoxylated thin-films on electron injection across organic interfaces

Abstract

The field of organic electronics has historically been frustrated by the difficulty and high cost of creating robust low work function cathode contacts on organic films. Traditional methods have been dominated by the vacuum deposition of highly reactive metals and subsequent device encapsulation against ambient conditions. However, recent research has demonstrated the use of polyethylenimine-ethoxylated (PEIE), a polymer surface modifier, as a means of reducing the work function of a wide variety of electrode materials. The fact that PEIE is stable in ambient conditions and can be deposited using simple spin-coating techniques opens up the possibility of all-polymer, solution processible organic electronics. The remainder of this work reports on the effects of PEIE thin-films on electron injection across material interfaces in a variety of organic electronic devices. Because it serves as the mechanism by which charge carriers are introduced into the organic semiconducting material, charge injection at the electrode/organic interface is central to the operation of a host of organic devices. Ultimately, the PEIE thin-films were found to consistently increase the amount of electron injection by up to three orders of magnitude.