Electroless surface polymerization of polyaniline films on aniline primed ITO electrodes: a simple method to fabricate good modified anodes for polymeric light emitting diodes

Polyaniline (PANI) films were prepared by electroless surface polymerization of the aniline on an aniline–silane (C6H5NHC3H6Si(OMe)3) modified (aniline primed) ITO electrode. Dense, smooth and strongly adhered films with thickness in the range of 100 nm to 1 µm were isolated. The polyaniline films deposited on aniline primed ITO electrodes (polyaniline/ITO) have a smoother surface, higher electrochemical activity and stability than those deposited on unmodified ITO electrodes or spin casting polyaniline films. The PANI films on ITO electrodes are very stable. The contamination on a used PANI/ITO modified electrode can be easily removed by washing the electrode with proper solvents and then drying under vacuum. Polyaniline film deposited on an aniline primed ITO electrode was used as a modified anode in a polymeric light emitting diode (PLED), which used poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) as an emitting layer and Al as a cathode. The PLED device, tested at an ambient atmosphere, has a turn on voltage 2.0 V lower than that of a device without a polyaniline interlayer. A PLED device using polyaniline/ITO as an anode can also sustain higher electric current, is more stable toward on/off switching, and has a better reproducibility compared to those without a polyaniline layer or using solution cast polyaniline film as an anode modification layer.