Doping conjugated polymers have attracted significant academic and industrial interest for their broad and various optoelectronic applications. In this regards, molecular doping by blending conjugated polymers and dopants has long been established as a general approach for the generation of free charge carriers. In blending system, however, the formation of polymer-dopant aggregates reduces doping efficiency at high dopant concentration, which consequently limits optimization of electrical conductivity. In this presentation, diffusion controlled sequential molecular doping for efficient conjugated polymers doping by utilizing strong intercalation between polymer matrix and dopant molecules will be introduced. In addition, effects of morphology and crystallinity of conjugated polymers on the electrical conductivity and thermoelectric power generation will be presented.