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

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.