Reduced threshold voltages and enhanced mobilities in diketopyrrolopyrrole-dithienothiophene polymer-based organic transistor by interface engineering

Flexible and low-power consuming integrated circuits are some of the basic requirements for smart wearable devices. High mobility solution-processed organic field-effect transistors (OFETs) have the potential to make a big impact in printed electronic circuits, but their overall performance is currently limited by unusually high threshold voltages V${}_{th}$. Herein, systematic optimization of donor-acceptor conjugated polymer, based on dithienothiophene (DTT) and thiophene-flanked diketopyrrolopyrrole (DPP), namely, PDPPT-DTT, OFETs by application of self-assembled monolayers (SAMs) at the semiconductor-dielectric, and semiconductor-metal interfaces is reported. The results clearly exhibit that simultaneous application of octyltrichlorosilane (OTS) as semiconductor-dielectric interface modifying layer and pentafluorobenzene thiol (PFBT) as semiconductor-metal interface modifying layer results in significantly lower V${}_{th}$ and subthreshold slope values from -14.07 V and 13.26 (V Dec${}^{-1}$) to +1.06 V and 7.11 (V Dec${}^{-1}$), respectively. This tailored approach is also beneficial in enhancing hole mobility values by an order of magnitude from 0.01 to 0.5 cm${}^2$ V${}^{-1}$ s${}^{-1}$ along with the possibility of switching from hole accumulation mode (V${}_{th}$ = -3.75 V) to depletion mode (V${}_{th}$ = +1.06 V) through device engineering. Simultaneous interface engineering reveals OFET electronic properties can be fine-tuned for robust circuits and low power electronic applications. (© 2020 Wiley‐VCH GmbH)