Unsubstituted polythiophene (PT) with defined and known high molecular mass (up to ca. 36 000 g mol(-1) (M-w)) and low structural defects (ca. 3.6 mol %) as highly attractive semiconducting material is presented. The new synthetic strategy for this polymer is based on the combination of Stille-type polycondensation reactions, ultrasound-assisted dispersion technique, and microwave-assisted ring-closure reactions. The use of Stille-type polycondensation produces a diketal prepolymer with good solubility and prescient and controllable degree of polymerization (DP) for the final insoluble PT. Ultrasonication preserves a high interfacial area, while microwave provides fast and effective heating for the last heterophase ring-closure reaction. The characterization of the final product by solid-state NMR, TEM, UV-vis absorption and fluorescence emission spectroscopy, XRD, TGA, and conductivity measurements exhibits significant features for electronic and photoelectronic applications, such as broadened absorption, relatively high crystallinity, high thermal stability, and typical semiconducting properties.