Nanoscale alignment of semiconductor crystals for high-fidelity organic electronics applications

Abstract

In this work, we report for the first time the combination of silicon dioxide (SiO2) nanoparticles and poly (styrene-block-4-vinylpyridine) (PS-b-P4VP) block copolymer supplements to tune random crystal growth and improve charge transport of small-molecule organic semiconductors. We chose 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) as a model semiconductor material to combine with both supplements. This led to a rigid alignment of the crystals that extended in long-range order as well as an increased coverage of the charge transport channel. In particular, the addition of 5% PS-b-P4VP supplement contributed to a low irregularity angle of 8.8° ± 6.7°, which indicates an 80% reduction of crystal random orientation. Bottom-gate, top-contact organic thin film transistors (OTFTs) based on the TIPS-PEN/SiO2/PS-b-P4VP combination film showed an average hole mobility of up to 0.033 ± 0.02 cm2/Vs and a 50% improvement of charge transport fidelity. The improved charge transport of TIPS-PEN crystals can be ascribed to both increased channel coverage due to the uniformity property of PS-b-P4VP polymer, and an effective nanoscale confinement of the random crystal growth due to the aggregation of nanoparticles. The facile method we reported in this work can be applied to manipulate the crystal growth and charge transport of the general solution-processed, small-molecule semiconductors for high-fidelity organic electronics applications on flexible substrate.