| Conjugated polymers with a ladder-type framework possess a two-dimensional geometry and are thus intermediate between linear and three-dimensional systems. The steric inhibition of electron delocalization is drastically reduced as the limited conformational freedom of conjugated ladder-type polymers. The ladder-type polymers with such a regular structure can get widely applications in many optic and electronic fields such as polymer light-emitting diodes, field-effect transistors, plastic lasers and photovoltaic devices. These polymers are of considerable current interest in the corresponding fields both in chemistry and physics, and many research works about these polymers have been reported in the past decade. In this thesis, we prepared a type of ladder-type poly(p-phenylenes) with fluorene units in polymer backbone by Suzuki coupling and presented full characterization of their structure and properties. The polymers have high molecular weights, low defect in backbone, excellent thermal stability, and good solubility in common organic solvents. The low-energy emission band from the aggregation of planar polymers or keto defect sites can't exert an effective influence to the photoluminescence spectra of LPFs. These attractive properties established the LPFs as widely useful materials for polymer-based optical and elcetro-optical applications. Light-emitting devices using LPFs as the active layer show blue-green emission. The self-absorption effect can be avoid by reducing the thickness of emission layer of the single-layer light-emitting device. Further improvement in device efficiency and brightness is obtained by introducing the electron transfer layer and hole block layer. The multi-layer devices show a maximum luminance efficiency of 2.56 cd/A. We also prepared a novel kind of semi-ladder poly(p-phenylene)s containing carbazole moieties with a facile and short synthetic strategy. The backbone of the polymer contained...
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