Thieno[3,2‐b]thiophene Flanked Isoindigo Polymers for High Performance Ambipolar OFET Applications

Abstract

The synthesis of a new thieno[3,2‐b]thiophene isoindigo (iITT) based monomer unit, and its subsequent incorporation into a series of alternating copolymers is reported. Copolymerisation with benzothiadiazole, bithiophene and thiophene comonomer units by palladium catalysed cross coupling gives three new narrow band gap semiconducting polymers for OFET applications. Extending the fused nature of the isoindigo core serves to further enhance molecular orbital overlap along the polymer backbones and facilitate good charge transport characteristics thus demonstrating the potential of extending the fused ring system that is attached to the isoindigo core. When used as the semiconducting channel in top‐gate/bottom‐contact OFET devices, good ambipolar properties are observed, with hole and electron mobilities up to 0.4 cm2/Vs and 0.7 cm2/Vs respectively. The three new polymers show good stability, with high temperature annealing showing an increase in the crystallinity of the polymers which corresponds directly to charge carrier mobility improvement as shown by X‐ray diffraction, atomic force microscopy and photothermal deflection spectroscopy.

Thiophene-fused isoindigo based conjugated polymers for ambipolar organic field-effect transistors

“…14 Further extension of the π-conjugated system (benzothiophene-fused isoindigo and benzofuran-fused isoindigo, Scheme 1c and d) led to small molecular OFETs with electron mobility up to 0.074 cm 2 V −1 s −1 under ambient conditions. 15 More recently, similar modifications on the isoindigo core were also reported (Scheme 1e-g) including thieno [3,2-b]thiophene isoindigo, 16 benzothienoisoindigo, 17 and thieno [3,2-b]- [1]benzothiophene isoindigo. 18 OFET devices fabricated with small molecules and polymers based on these structures all showed promising performances.…”

“…18 OFET devices fabricated with small molecules and polymers based on these structures all showed promising performances. [16][17][18] All this progress indicates the great potential of isoindigo core modification in improving OFET properties, which deserves further exploration.…”

Recent Progress in High‐Mobility Organic Transistors: A Reality Check

“…To avoid using supramolecular locks for planarizing the conjugated backbone, benzene rings can be substituted in isoindigo by thieno[3,2‐ b ]thiophene, reducing the steric hindrance between adjacent building blocks in the polymer backbone ( P21 ) . The thieno[3,2‐ b ]thiophene isoindigo (iITT) containing polymers ( P22 ) exhibit good ambipolar charge transport with hole and electron mobilities up to 0.4 cm 2 V −1 s −1 and 0.7 cm 2 V −1 s −1 , respectively …”

“…Finally, Meager et al suggested that extending the fused nature of the isoindigo core is a good way to enhance charge transport because this improves the molecular overlap along the polymer backbone. They modified the peripheral phenyl ring of isoindigo to a fused thieno[3,2‐ b ]thiophene and its subsequent copolymerizations, demonstrating n‐type mobilities of 0.7 cm 2 V −1 s −1 in top‐gate bottom‐contact OTFTs from copolymerization with benzothiadiazole ( P22) …”

The Effect of Random and Block Copolymerization with Pendent Carbozole Donors and Naphthalimide Acceptors on Multilevel Memory Performance

“…Owing to several advantages, such as excellent solution processability, low power consumption, structural tunability, and 3D stacking capabilities, polymeric materials have been widely applied in electronic devices, such as organic solar cells (OSCs), organic field‐effect transistors (OFETs), organic light‐emitting diode (OLEDs), and organic memory devices (OMDs) . However, to date, most polymer‐based OMDs have only exhibited the traditional binary memory behavior, which cannot meet the ever‐increasing global demands for data storage.…”