Conjugated polymers with thiazolothiazole as the acceptor unit for high performance organic solar cells

In this study, we used a simple, cost-effective, and high-yield synthetic route to successfully synthesize two thiazolothiazole-based wide-bandgap donor polymers, namely TTZ and ANTTZ. We systematically investigated how the solubility, absorption and photoelectric properties of the materials were influenced by the position of ester group at the thiophene unit as π-bridge. Theoretical calculations, UV-vis spectroscopy and GIWAXS results revealed that TTZ possesses planar molecular backbone and higher crystallinity. Ultimately, with BTP-ec9-4F as the acceptor, the TTZ based devices can achieve an impressive power conversion efficiency (PCE) of 13.96%; whereas the ANTTZ based devices can give a PCE of only 3.07%. This research underscores the effectiveness of a cost-efficient donor material synthesis route and highlights the crucial influence of the side chain position on crystallinity of the polymer, offering a new direction for designing low-cost, high-efficiency photovoltaic materials.