A microfluidics applicator is used in the fabrication of a polyfluorene based polymer light emitting diode (PLED). This procedure results in a single contiguous polymer trace and, as a consequence of the high deposition speed, shows unusual characteristics in both the film morphology and polymer microstructure. These aspects are studied using fluorescence microscopy, profilometry, and optical absorption and emission spectroscopies. Room temperature analysis of the poly(di--octylfluorene) indicates that the combination of high-speed deposition and rapid drying process traps the polymer into a metastable conformational state. Optical spectroscopy at reduced temperature identifies emission from at least two distinct conformational chromophores. At elevated temperature there is an abrupt, irreversible transition to a more conventional structural form. Electroluminesence data from PLED test devices are shown and this demonstrates some of the unique opportunities afforded by this method of polymer film formation and device fabrication. Device operation is not optimized.
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Chen et al. use only toluene in their study whereas chlorobenzene, used in our work, has a much lower vapor pressure and is hence more difficult to effect a “rapid” drying.
