Synthesis and Application of Dithieno[2,3‐<i>d</i>:2′,3′‐<i>d</i>′]Benzo[1,2‐<i>b</i>:4,5‐<i>b</i>′]‐Dithiophene‐Alt‐Halogenated‐Dithieno[3,2‐<i>a</i>:2′,3′‐<i>c</i>]Phenazine Conjugated Polymers for Organic Solar Cells

ABSTRACT Two wide band gap conjugated polymers labeled PDBT‐DTPz‐Cl and PDBT‐DTPz‐F, deriving from 4,8‐di(5‐(2‐butyloctyl)‐4‐chlorothiophen‐2‐yl)dithieno[3,2‐ d ,3′,2′ ‐d ′]benzo[1,2‐ b ;4,5‐ b ′]dithiophene and 9,10‐dichloro‐2,5‐bis((4‐hexyldecyl)thiophen‐2‐yl)dithieno[3,2‐ a :2′,3′‐ c ]phenazine or 9,10‐difluoro‐2,5‐bis((4‐hexyldecyl)thiophen‐2‐yl)dithieno[3,2‐ a :2′,3′‐ c ]phenazine, are synthesized by the Palladium‐catalyzed Stille coupling reaction, and characterized by UV–vis absorption, gel chromatography (GPC) and cyclic voltammetry (CV) etc. The polymers exhibit extensive light‐harvesting ability in the region of 300–700 nm alongside the lowest unoccupied (LUMO) and highest occupied molecular orbital (HOMO) energy levels of −3.92 and −5.59 eV for PDBT‐DTPz‐Cl and −3.98 and −5.65 eV for PDBT‐DTPz‐F. Besides that, the non‐fullerene‐based organic solar cells (NFAs‐OSCs) from the blends of PDBT‐DTPz‐Cl:Y6 and PDBT‐DTPz‐F:Y6, which respectively present efficiencies of 9.41% and 13.16%, were achieved. The enhanced performance of devices fabricated from PDBT‐DTPz‐F:Y6, as compared to those from PDBT‐DTPz‐Cl:Y6, is attributed to several key factors. These include the higher charge mobility of the blend films, the increased probability of exciton dissociation, and the reduced bimolecular, triplet‐assisted recombination, and non‐radiative energy losses. These improvements are thoroughly discussed and corroborated by a comprehensive suite of physical measurements.