High-performance amorphous donor-acceptor conjugated polymers containing x-shaped anthracene-based monomer and 2,5-bis(2-octyldodecyl)pyrrolo[3,4-c] pyrrole-1,4(2H,5H)-dione for organic thin-film transistors

New diketopyrrolopyrrole (DPP)-containing amorphous conjugated polymers, such as poly(3-(5-((9,10-bis((4-hexylphenyl)ethynyl)-6-(prop-1-ynyl)anthracen-2- yl)ethynyl) thiophen-2-yl)-5-(2-hexyldecyl)-2-(2-octyldodecyl)-6-(thiophen-2-yl) pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione) (4), and poly(3-(5-((2,6-bis((4- hexylphenyl)ethynyl)-10-(prop-1-ynyl)anthracen-9-yl)ethynyl)thiophen-2-yl)-2, 5-bis(2-octyldodecyl)-6-(thio phen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione) (7), were successfully synthesized via Sonogashira coupling reactions under microwave conditions. Copolymer 7, incorporating a DPP moiety at the 9,10-position of the anthracene ring through a triple bond, showed a much lower bandgap energy (E _g = 1.81 eV) than copolymer 4 (E _g = 2.13 eV). Tuning of the molecular frontier orbital energies was achieved by only changing the anchoring position of dithiophenyl-DPP from the 2,6- to the 9,10-position in the anthracene ring. Because of the donor-acceptor (D-A) interaction and the two-dimensional planar structure of the X-shaped donor monomer, the resulting polymers showed good interchain π-π stacking in the thin-film state, despite being amorphous polymers. When the newly synthesized polymer 7 was used as a semiconductor material in an organic thin-film transistor, the best mobility of up to 0.12 cm ² V ^-1 s ^-1 (I _on/off = ∼ 4.4 × 10 ⁶) was observed, which is one of the highest values recorded for amorphous polymer films reported to date.