Carrier transport in poly(p-phenylenevinylene) (PPV) and at a PPV/Al interface from impedance spectroscopy

Impedance spectroscopy has been used to study the charge transport mechanism for poly(p-phenylenevinylene) (PPV) and its interface with aluminum. By separating the bulk and the interface contributions, the bulk and junction resistance and capacitance have been determined at various temperatures. The dependence of bulk d.c. conductivity on temperature yields an activation energy of 0.36 eV, which implies that interchain hopping is the dominant transport process in PPV. It is also found that the slower relaxation process occurs at the interface, which limits the carrier injection across the Al/PPV junction. The observation of high interfacial resistance and low electron mobility in PPV leads to the conclusion that most of the electron-hole recombination occurs at the Al/PPV junction, thus lowering the efficiency and lifetime of electroluminescent display devices based on PPV.