Dithienocyclopentathieno[3,2-b]thiophene Hexacyclic Arene for Solution-Processed Organic Field-Effect Transistors and Photovoltaic Applications

We have developed a ladder-type dithienocyclopentathieno[3,2-b]thiophene (DTCTT) hexacyclic unit in which the central thieno[3,2-b]thiophene ring was covalently fastened to two adjacent thiophene rings through carbon bridges, thereby forming two connected cyclopentadithiophene (CPDT) units in a hexacyclic coplanar structure. This stannylated Sn-DTCTT building block was copolymerized with three electron-deficient acceptors, dibromo-thieno[3,4-c]pyrrole-4,6-dione (TPD), dibromo-benzothiadiazole (BT), and dibromo-phenanthrenequinoxaline (PQX), by Stille polymerization, thereby furnishing a new class of alternating donoracceptor copolymers: PDTCTTTPD, PDTCTTBT, and PDTCTTPQX, respectively. Field-effect transistors based on PDTCTTPQX and PDTCTTBT yielded high hole mobilities of 0.017 and 0.053 cm2?V-1?s-1, respectively, which are among the highest performances among amorphous donoracceptor copolymers. A bulk heterojunction solar cell that incorporated PDTCTTTPD with the lower-lying HOMO energy level delivered a higher Voc value of 0.72 V and a power conversion efficiency (PCE) value of 2.59?%.