We investigate the fundamental properties of conjugated-polymer semiconductors from the novel viewpoint of solid-state ab initio approaches, that are appropriate for extended and crystalline systems. The impact of interchain interactions on optics and transport of these materials is analyzed by developing computational schemes for transfer integrals and exciton states. We focus on a prototype polymer of great interest for optoelectronics, poly-para-phenylenevinylene (PPV), and compare different solid-state packings, where the character of interactions ranges from quasi-one-dimensional to quasi-three-dimensional. Interchain coupling is found to control light emission and charge conduction, and can thus be used as a tunable parameter for the design of devices based on organic materials.
