NIR spectrophotometry characterization of ITO electronic property changes at the interface with a PPV derivative

The electronic effects at polymer/indium tin oxide (ITO) interface play a crucial role in light-emitting devices as controlling charge injection. Near-infrared spectrophotometry has been used to characterize the modifications of the ITO electronic properties induced by the deposition of a PPV derivative. Near-infrared (NIR) spectra have been analyzed using Drude free electron theory providing information on the free carriers density and local conductivity. The optical analysis reveals a 10% reduction of the ITO free carrier concentration at the contact with the PPV derivative, which has been attributed to the formation of a polarization layer at the interface. Comparison has been done between polymer deposited directly on ITO or on ITO functionalized with a phosphonic acid layer (SAM) to improve the electronic/polymer interface. The NIR study indicates that charge transfers occur with the first deposited layer, providing confirmation of an interface effect. (C) 2003 Elsevier Science B.V. All rights reserved.