A Strategically Designed Easily‐Synthesized Polymer Donor for Efficient Organic Photovoltaics

Recent advances in donor and acceptor materials have significantly boosted power conversion efficiency (PCE) of organic photovoltaics (OPVs). However, high‐performance materials are often composed of multi‐fused heteroaromatic rings, necessitating long synthetic steps and complex synthetic procedures, thereby increasing production costs. Here, a polymer donor is strategically designed and synthesized, named PTz3TE, with a simplified chemical structure featuring thiazolothiazole–terthiophene backbones and ester side chains. Remarkably, PTz3TE can be synthesized from commercially available materials in just seven steps without the need for very‐low‐temperature reactions, such as below −30 °C, and chromatographic purification, and exhibits PCEs reaching 18%, a notably high efficiency for a polymer with such a simple structure and synthetic route. With a quantitative assessment of synthetic complexity, PTz3TE is confirmed as one of the most cost‐effective polymer donors. Findings offer valuable insights for the commercialization of OPVs.