Direct arylation polymerization toward efficient synthesis of benzo[1,2‐c:4,5‐c'] dithiophene‐4,8‐dione based donor‐acceptor alternating copolymers for organic optoelectronic applications

Abstract

Wide‐bandgap π‐conjugated donor‐acceptor (D‐A) alternating copolymers consisting of benzo[1,2‐c:4,5‐c']dithiophene‐4,8‐dione (BDTD) as the electron‐accepting building block have demonstrated outstanding performances in organic bulk heterojunction (BHJ) solar cell devices. But the synthesis of these polymers has been largely limited to conventional polymerization techniques, particularly Stille‐coupling based polycondensations, which often involve tedious preactivation of C‐H bonds using highly flammable reagents such as butyl lithium and highly toxic reagents such as trialkyl tin chlorides. Herein, we report a “greener” synthetic route of direct arylation polymerization to a series of wide bandgap D‐A copolymers with a common acceptor building block of BDTD. The structure–property relationship in these polymers is characterized. We also present the device performances of these polymers in both thin‐film field‐effect transistors and organic BHJ solar cells involving the BDTD‐based polymers as the electron donors and fullerene derivatives as the electron acceptors. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2554–2564

Aqueous Palladium‐Catalyzed Direct Arylation Polymerization of 2‐Bromothiophene Derivatives

“…CH bond activation [ 1–5 ] has attracted extensive attention in organic syntheses. [ 6–11 ] Particularly, palladium‐catalyzed direct arylation involves coupling of the aryl halide with the sp 2 ‐sp 2 CH functionality to accomplish aryl–aryl bond formation. [ 12–18 ] Concerted metalation deprotonation (CMD) is a possible mechanism for CH bond activation, [ 19–23 ] with deprotonation of the aryl moiety by the carboxylate/carbonate and metalation to Pd occurring concurrently.…”

Direct C–H Arylation-Derived Donor Polymers Afford PCEs over 10% for Organic Solar Cells

“…Direct C–H arylation polymerization (DArP) (i.e., C–H/C–Br cross coupling), featured by higher atomic economy, fewer synthetic steps, and simpler byproduct (i.e., HBr), has emerged as a sustainable synthetic protocol for the small molecules, − oligomers, − and polymers ,− used in OSCs. However, up until now, most of the DArP-synthesized polymer donors only exhibited PCEs less than 10% in OSC devices, as shown in Table . ,− PBDB-T2F (also known as PM6) is a D-π– A type copolymer, involving bis-2-ethylhexyl thiophene-substituted benzodithiophene (BDT-F), thiophene, and 1,3-bis­(4-(2-ethylhexyl) thiophen-2-yl)-5,7-bis (2-alkyl)­benzo­[1,2-c:4,5-c′]­dithiophene-4,8-dione (BDD) as building blocks, which represents one of the most widely used polymeric donors used in OSCs that can well cooperate with varied nonfullerene acceptors (NFAs). − Typically, PM6 is synthesized via C–Sn/C–Br Stille coupling polymerization between monomers of BDT-2F distannide (BDT-2F-diSn) and BDD dibromide (BDD-diBr) . Searching for atom-economic synthetic protocols with minimized waste emission and high device performance will thus be highly desirable for the scalable application of this benchmark polymeric donor.…”

Design Principles for the Acceptor Units in Donor–Acceptor Conjugated Polymers

“…Compounds are identified as follows: A1 , 1,3,4-oxadiazole; A2 , 1,3,4-thiadiazole; A3 , 3,6-dihydro-1,2,4,5-tetrazine; A4 , thiazolo[5,4- d ]thiazole; A5 , 2,2′-bithiazole; A6 , benzo[ c ][1,2,5]thiadiazole; A7 , [1,2,5]thiadiazolo[3,4- c ]pyridine; A8 , 5-fluorobenzo[ c ][1,2,5]thiadiazole; A9 , 5,6-difluorobenzo[ c ][1,2,5]thiadiazole; A10 , 5-ethoxybenzo[ c ][1,2,5]thiadiazole, A11 , 5,6-diethoxybenzo[ c ][1,2,5]thiadiazole; A12 , naphtho[1,2- c :5,6- c ′]bis([1,2,5]thiadiazole); A13 , benzo[ c ][1,2,5]selenadiazole; A14 , benzo[ c ][1,2,5]oxadiazole; A15 , 2,2-dimethyl-2 H -benzo[ d ]imidazole; A16 , 2 H -benzo[ d ][1,2,3]triazole; A17 , 2-methyl-2 H -benzo[ d ][1,2,3]triazole; A18 , 2-ethyl-2 H -benzo[ d ][1,2,3]triazole; A19 , 2-propyl-2 H -benzo[ d ][1,2,3]triazole; A20 , 5,6-difluoro-2-methyl-2 H -benzo[ d ][1,2,3]triazole; A21 , 2,7-dimethyl-2,7-dihydronaphtho[1,2- d :5,6- d ′]bis([1,2,3]triazole); A22 , quinoxaline; , A23 , pyrido[3,4- b ]pyrazine; A24 , 2,3-dimethylpyrido[3,4- b ]pyrazine; A25 , 2,3-difluoroquinoxaline; A26 , pyrazino[2,3- g ]quinoxaline; A27 , 3 a ,4-dihydrothieno[3,4- b ]thiophene; A28 , 5,7-dihydrothieno[3,4- b ]pyrazine; A29 , 5,5-dimethyl-4 H -cyclopenta[ c ]thiophene-4,6(5 H )-dione; A30 , 5-methyl-4 H -thieno[3,4- c ]pyrrole-4,6(5 H )-dione; , A31 , 5-methyl-4 H -thieno[3,4- c ]pyrrole-4,6(5 H )-dione; A32 , naphtho[2,3- c ]thiophene-4,9-dione; A33 , 2,5-dimethylpyrrolo[3,4- c ]pyrrole-1,4(2 H ,5 H )-dione; A34 , ( E )-1,1′-dimethyl-[3,3′-biindolinylidene]-2,2′-dione; A35 , 2-methylisoindoline-1,3-dione; A36 , 3 a ,7 a -dihydrobenzo[1,2- d :4,5- d ′]bis(thiazole); A37 , 3 a ,7 a -dihydrobenzo[1,2- d :4,5- d ′]bis(thiazole); , A38 , 6-methyl-6,8-dihydro-4 H -[1,2,3]triazolo[4′,5′:4,5]benzo[1,2- c ][1,2,5]oxadiazole; A39 , 2,6-dimethyl-2,4,6,8-tetrahydrobenzo[1,2- d :4,5- d ′]bis([1,2,3]triazole), A40 , 6,7-dimethyl[1,2,5]thiadiazolo[3,4- g ]quinoxaline; A41 , 6-methyl-6,8-dihydro-4 H -[1,2,3]triazolo[4′,5′:4,5]benzo[1,2- c ][1,2,5]thiadiazole; A42 , 6-methyl-6,8-dihydro-4 H -[1,2,3]triazolo[4′,5′:4,5]benzo[1,2- c ][1,2,5]selenadiazole; A43 , 4 H ,8 H -benzo[1,2- c :4,5- c ′]bis([1,2,5]thiadiazole); A44 , 2,7-dimethylbenzo[ lmn ][3,8]phenanthroline-1,3,6,8(2 H ,7 H )-tetraone; A45 , 5-methyl-6 a ,9 a -dihydro-4 H -thiazolo[4,5- c ]thieno[2,3- e ]azepine-4,6(5 H )-dione; A46 , 2,6-dimethyl[1,2,3]triazolo[4,5- f ]isoindole-5,7(2 H ,6 H )-dione; A47 , dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2- c ][1,2,5]oxadiazole; A...…”