In this presentation we report the realization of novel semiconductor materials, as well as thin-film processing and morphology engineering, for flexible and stretchable organic electronic devices such as thin film transistors, solar cells, electrolyte gated transistors, sensors and neuromorphic circuits. On material development, we present “soft” small-molecules and polymers by co-polymerizing pi-deconjugated building blocks, properly designed additives and tuned backbone conformation. New transistor architectures using semiconductor film porosity as the key element for enhancing mechanical flexibility and tune charge transport are also demonstrated. These films, combined with pre-stretched elastomeric substrates, enabling unprecedentedly stable current-output characteristic upon mechanical deformation, which are used for sensing analytes, strain, light, temperature and physiological parameters. Furthermore, we report our recent work on the design of fluorinated acceptors for organic solar cells and a new route to achieve ultra-stretchable solar cell devices. Finally, we report our recent work on molecular n-doping of organic semiconductors using a novel strategy involving catalysts.