Over the last few decades, significant progress has been made in the design, synthesis and application of organic semi-conducting materials containing electron-rich (donor D) and electron-deficient (acceptor A) alternating units. However, there is still a need for the elaboration of new and innovative building blocks in order to enlarge the field of applications of conjugated materials. In the present work, the incorporation of thiazole as an original π-conjugated fragment is addressed. In particular, we describe an intensive and complete study about its chemical reactivity, using dedicated direct arylation cross-coupling catalysis. It is noteworthy that despite its unsymmetrical nature, successful control of the orientation of thiazole along the conjugated backbone was attained without requiring any protection step. Furthermore, we present an investigation on how the orientation of thiazole impacts the optical properties of thiazole containing semiconducting materials.[1] Finally, it has been found that the thiazole moiety allows to lower both HOMO and LUMO levels, relative to the thiophene-based counterpart, while keeping the energy band gap almost unchanged.[2] For the first time, these features are used to increase photovoltaic performances of small molecules based bulk heterojunction compared to thiophene counterparts, leading to a higher power conversion efficiency for soluble small molecules-based devices. [1]Chávez, P.; Ngov, C.; De Frémont, P.; Lévêque P. and Leclerc, N. J. Org. Chem., 2014, 79, 10179-10188 [2]Zaborova, E.; Chávez, P.; Bechara, R.; Lévêque, P.; Heiser, T.; Méry, S.; Leclerc, N. Chem. Commun. 2013, 49, 9938-9940.