Tuning of metal work functions with self-assembled monolayers

Work functions of gold and silver are varied by over 1.4 and 1.7 eV, respectively, by using self-assembled monolayers. Using these modified electrodes, the hole current in a poly(2-methoxy-5-(2'-ethylhexyloxy)- 1,4-phenylene vinylene) light-emitting diode is tuned by more than six orders of magnitude (see Figure). Suppression of the hole current enables measurement of the electron current in a polymer/polymer blend photovoltaic cell.