Abstract : We study the interplay between morphology of the organic layer and carrier transport. Two methods have been used to determine carrier mobility : time of flight and field effect transistor characterizations. The first part of this study concerns polymers derived from fluorene. New copolymers based on fluorene and fluorenone have been synthesized to enhance p-stacking, and thus excimer and/or aggregate formation. This helps us to understand the origin of the red-shifted emission occurring with fluorene. Moreover, we present the bright yellow and efficient luminescence property of this copolymer. An analogy with poly(alkylthiophene) allows us to understand the limits of carrier transport in films based on fluorene derived materials. Finally, we study the interplay between morphology and transport in two polymers derived from thiophene : thiophene-bipyridine copolymers and soluble fractions of polythiophene gels.