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 polymerizatio n of the aniline on an aniline-silane (C6H5NHC3H6Si(OMe)(3)) modified (anil ine primed) ITO electrode. Dense, smooth and strongly adhered films with th ickness in the range of 100 nm to 1 mum were isolated. The polyaniline film s deposited on aniline primed ITO electrodes (polyaniline/ITO) have a smoot her surface, higher electrochemical activity and stability than those depos ited on unmodified ITO electrodes or spin casting polyaniline films. The PA NI films on ITO electrodes are very stable, The contamination on a used PAN I/ITO modified electrode can be easily removed by washing the electrode wit h proper solvents and then drying under vacuum. Polyaniline film deposited on an aniline primed ITO electrode was used as a modified anode in a polyme ric light emitting diode (PLED), which used poly[2-methoxy-5-(2-ethylhexylo xy)-1,4-phenylenevinylene] (MEH-PPV) as an emitting layer and Al as a catho de. 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 reproduci bility compared to those without a polyaniline layer or using solution cast polyaniline film as an anode modification layer.