No abstract

Organic thin-film transistors (OTFTs) are essential components for future flexible/wearable electronics. To fabricate OTFTs in an industrial level, following requirements should be met: high carrier mobility, low-voltage operation, compatibility with a reliable high-resolution patterning process, and high mechanical and electrical stability. Here, we report the synthesis of six-branched cross-linkers (6Bx) having an ultrahigh photocross-linking efficiency and its application to photo-patterning gate dielectric (GD) polymers and channel semiconducting (CS) polymers in polymer-based OTFTs. The use of 6Bx permits the generation of a high-resolution-patterned ultra-thin polymer gate dielectric with a low leakage current (7 × 10 −9 A cm −2 at 1 MV cm −1 ). Moreover, cross-linking the GD polymer interfaced with p-or n-type CS polymer induces alignment of CS polymer chains at the interface. This yields excellent hole and electron mobilities of 12.42 and 10.11 cm 2 V −1 s −1 , respectively, from p-and n-type OTFTs operated at <3 V, which are remarkably improved carrier mobilities at substantially low operation voltages compared to those by conventional test beds. Further, the fabrication of logic gates and ring oscillators demonstrates the reliability of polymer OTFTs cross-linked with 6Bx. This work presents a universal strategy for high mobility, reliable, and low-voltage operating OTFTs.

A low‐bandgap PBDTDTPD polymer is synthesized. It is a donor‐acceptor‐type polymer that consists of dialkylthiophenyl benzodithiophene (BDT) donor unit and N‐octyl‐2,7‐dithia‐5‐aza‐cyclopenta[a]pentalene‐4,6‐dione (DTPD) acceptor unit. The thienothiophene‐fused strong‐electron‐withdrawing DTPD effectively reduces the bandgap of the resulting polymer and keeps its highest occupied molecular orbital low. Moreover, PBDTDTPD is thermally stable and dissolves well in typical organic solvents. PBDTDTPD:PC71BM(1:1) blend film showed a power conversion efficiency of 3.18% and a largely elevated open‐circuit voltage of 0.75 V compared to that of well‐known P3HT:PC61BM blend film. In this work, we prove that the DTPD moiety can be utilized to develop a future low‐bandgap material that can absorb a broad wavelength of light and have high thermal stability, which are important characteristics for next‐generation high‐performance organic solar cells.