Conductive polymers are an established technology with applications reaching from transparent electrodes and active materials for LED's and solar cells to light-weight batteries. In this thesis, the focus lies with intrinsically doped, (semi-) transparent polymers. The development of a new deposition method based on oxidative chemical vapour deposition (oCVD) and its application to thiophene-based systems is the presented. The innovation in this process lies with the use of sulphuric acid acting as both, the oxidizing/polymerizing agent and dopant in oCVD. In this way, sulphate ions are integrated into the polymer matrix, leading doping and crystallization in dimensions hitherto unprecedented. Thereby, the small dopant also reduces disorder and in turn promotes extraordinary electron charge-carrier transport properties. Here, the progress on three thiophene-based polymers is presented: poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenediothiathiophene) (PEDTT), and poly(thieno[3,4b]pyrazine) (PTP). PEDOT:sulphate presents the most extraordinary of the three, with a conductivity of more than 4000 S/cm at room temperature and an impressive 3300 S/cm at 1.8 K. It was possible to show, that this polymer operates in the metallic regime of the metal-insulator-transition (MIT) and exhibits MC. Additionally it was possible to measure a Hall effect at low temperature: which is only possible in homogeneous materials of extraordinarily high conductivity and mobility. The same material was additionally measured in thick-films. In this case, a conductivity minimum and thus a transition to the true metallic state was revealed. The measurements in this system were repeated for high pressures, which resulted in further suppression of disorder and an improvement of electron transport properties. The second best material, PEDTT:sulphate was an achievement in itself, albeit not as impressive as PEDOT. With 1050 S/cm at room temperature, the previous record from 1995 was beaten 2600-fold. The most impressive about this result is that literature categorically dismissed the material as a good conductive system. In this case, sulphate does not only act as a dopant but also as a structurally stabilizing and disorder-suppressing entity. The material presents a conducting polymer in the critical regime of the MIT. At last, PTP presents the odd-one out in the series. Though exhibiting interesting properties in the context of adhesion to glass. In the context of conductivity, substantial disorder was detected, partially owed to the unprotected reactive sites apart from the thiophene ring.