Surface and Interfacial Properties in Thin Poly(p-Phenylene Vinylene) Multilayers Prepared by Self-Assembly Method

Abstract

ABSTRACTIn this work we report on the influence of interfaces (metal/film, ITO/film) on the optical properties of ultrathin layers of poly(p-phenylene vinylene), PPV, adsorbed by self-assembly. PPV films were prepared exploiting the self-assembly method (SA) in addition to a low temperature conversion process for PPV. Using atomic force microscopy we show that 0.5 nm thick PPV layers can be homogeneously deposited on different metals (50% transmission Au, Cu, Pt, Ag, Cr films), glass and ITO surfaces. Absorption measurements reveal that the transitions involving φ-φ* conjugated states are blue shifted to different extents depending on the interface and on the film thickness. This indicates different extensions of interfacial disorder in the PPV layers. The ITO/PPV interface has the highest extension for disorder (∼16 nm) and highest surface roughness (RMS∼2.5 nm) while the lowest values (∼5 nm and 0.6 nm, respectively) were found for the quartz/PPV interface. The metal interface induces significant luminescence quenching and spectral shifts, which depend on the type of metal used. The effect from incorporation of carbonyl and from chemical modifications of the ITO/organic interface during PPV thermal conversion is discussed.