title: Thieno[3,4-c]pyrrole-4,6-dione-based polymer semiconductors: toward high-performance, air-stable organic thin-film transistors.
abstract: We report a new p-type semiconducting polymer family based on the thieno[3,4-c]pyrrole-4,6-dione (TPD) building block, which exhibits good processability as well as good mobility and lifetime stability in thin-film transistors (TFTs). TPD homopolymer P1 was synthesized via Yamamoto coupling, whereas copolymers P2-P8 were synthesized via Stille coupling. All of these polymers were characterized by chemical analysis as well as thermal analysis, optical spectroscopy, and cyclic voltammetry. P2-P7 have lower-lying HOMOs than does P3HT by 0.24-0.57 eV, depending on the donor counits, and exhibit large oscillator strengths in the visible region with similar optical band gaps throughout the series (∼1.80 eV). The electron-rich character of the dialkoxybithiophene counits in P8 greatly compresses the band gap, resulting in the lowest E(g)(opt) in the series (1.66 eV), but also raising the HOMO energy to -5.11 eV. Organic thin-film transistor (OTFT) electrical characterization indicates that device performance is very sensitive to the oligothiophene conjugation length, but also to the solubilizing side chain substituents (length, positional pattern). The corresponding thin-film microstructures and morphologies were investigated by XRD and AFM to correlate with the OTFT performance. By strategically varying the oligothiophene donor conjugation length and optimizing the solubilizing side chains, a maximum OTFT hole mobility of ∼0.6 cm(2) V(-1) s(-1) is achieved for P4-based devices. OTFT environmental (storage) and operational (bias) stability in ambient was investigated, and enhanced performance is observed due to the low-lying HOMOs. These results indicate that the TPD is an excellent building block for constructing high-performance polymers for p-type transistor applications due to the excellent processability, substantial hole mobility, and good device stability.
authors.affiliation: Department of Chemistry and the Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Xugang
authors.initials: X
authors.lastname: Guo
authors.forename: Rocio Ponce
authors.initials: RP
authors.lastname: Ortiz
authors.forename: Yan
authors.initials: Y
authors.lastname: Zheng
authors.forename: Myung-Gil
authors.initials: MG
authors.lastname: Kim
authors.forename: Shiming
authors.initials: S
authors.lastname: Zhang
authors.forename: Yan
authors.initials: Y
authors.lastname: Hu
authors.forename: Gang
authors.initials: G
authors.lastname: Lu
authors.forename: Antonio
authors.initials: A
authors.lastname: Facchetti
authors.forename: Tobin J
authors.initials: TJ
authors.lastname: Marks