Microstructure tailoring of conjugated polymer-electrolyte blends for light-emitting electrochemical cells

We report on a strategy to reduce the size scale of the phase-separation in blends of conjugated polymers and solid state electrolytes. Blending a blue-green emitting conjugated polymer (methyl substituted ladder-type poly(p-phenylene), mLPPP) with a crown ether-based solid state electrolyte (Dicyclohexano18crown6 (DCH18C6), as an ion co-ordinating and transporting component and a Li salt, Lithium trifluoromethanesulfonate (Li triflate, LiTf for short) that provides the ionic species) evokes pronounced phase-separation. Endowing the backbone of mLPPP with convenient structural units largely reduces the size scale of this phase-separation. In particular we show that carbazole groups, which are generally applied in organic electronics to facilitate charge carrier transport, accessorily abate the tendency for phase-separation from a micro- to a sub-micro-scale. This attitude is investigated by UV/VIS/NIR absorption measurements, infrared spectroscopy, atomic force microscopy (AFM) and X-ray analysis by means of energy dispersive X-ray spectrometry (EDXS) in the scanning electron microscope (SEM).