Preparation of carbazole polymer thin films by electron-assisted deposition of 3-(N-Carbazolyl)propyl acrylate

Polymeric thin films having carbazole pendant groups were prepared by physical vapor deposition of 3-(N-carbazolyl)propyl acrylate (CPA). The conventional vacuum evaporation of CPA formed thin films that consist mainly of small molecules. The evaporated films had needlelike crystallites in the as-deposited state, and underwent severe coalescence upon annealing at 125 degrees C. The deposition polymerization of CPA was achieved by initiating polymerization by electron irradiation onto the monomer vapor by ionization-assisted deposition (IAD). Infrared analysis showed that the polymerization reaction was enhanced by increasing the electron current used for irradiation. The deposition polymerization was effective in improving the uniformity and thermal stability of the film. Photoluminescence analysis suggested that excimer formation can be suppressed by the deposition-polymerization of CPA. The deposited film was found to function as the hole transport layer of the organic light-emitting diode.