Interface evolution in the formation of low work function metal ohmic contacts on organic layers in photonic devices

Low work function metals are commonly used as electron-selective ohmic contacts with electron transport layers in molecular photonic and electronic devices such as organic photovoltaics (OPVs), organic light emitting diodes (OLEDs) and organic field effect transistors (OFETs). Although the fundamental charge injection physics of such interfaces have been well described, the interfacial chemistry associated with these contacts is poorly understood and characterized. Efforts to characterize the chemistry of such interfaces using surface Raman spectroscopy have been undertaken in this laboratory. In this presentation, chemistry associated with evolution of the interfaces in these ohmic contacts will be explored for the low work function metals Ag, Al, Ca and Mg with solid state organic thin films including simple organic model systems, ordered forms of carbon, and polymeric systems. Implications for device performance will be considered.