In this study, inorganic silica nanoparticles are used to manipulate the morphology of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS pentacene) thin fi lms and the performance of solution-processed organic thin-fi lm transistors (OTFTs). This approach is taken to control crystal anisotropy, which is the origin of poor consistency in TIPS pentacene based OTFT devices. Thin fi lm active layers are produced by drop-casting mixtures of SiO 2 nanoparticles and TIPS pentacene. The resultant drop-cast fi lms yield improved morphological uniformity at ∼ 10% SiO 2 loading, which also leads to a 3-fold increase in average mobility and nearly 4 times reduction in the ratio of measured mobility standard deviation ( μ Stdev ) to average mobility ( μ Avg ). Grazing-incidence X-ray diffraction, scanning and transmission electron microscopy as well as polarized optical microscopy are used to investigate the nanoparticle-mediated TIPS pentacene crystallization. The experimental results suggest that the SiO 2 nanoparticles mostly aggregate at TIPS pentacene grain boundaries, and 10% nanoparticle concentration effectively reduces the undesirable crystal misorientation without considerably compromising TIPS pentacene crystallinity.

We use 6,13-bis(triisopropylsilylethynyl)pentacene as a model small molecule organic semiconductor and two conjugated polymer additives to demonstrate conjugated polymer-mediated polymorphism of a small molecule organic semiconductor for the first time. The conjugated polymer additives, used with a slow solution crystallization approach, yield crystal structures that are not accessible by nonconjugated polymer additives and impart excellent long-range order. In both of the small molecule semiconductor/conjugated polymer blends studied here, previously unreported polymorphs of a small molecule semiconductor have been identified which also leads to improved charge transport in the absence of external alignment. These results open up a new exciting avenue to manipulate unit cell structure, long-range order, and charge transport of high performance, solution-processed, small molecule organic semiconductors.

Lateral and vertical phase separations play critical roles in the performance of the next-generation organic and hybrid electronic devices. A method is demonstrated here to switch between lateral and vertical phase separations in semiconducting 6,13-bis(triisopropylsilylethynyl) pentacene (TIPSE pentacene)/polymer blend films by simply varying the alkyl length of the polyacrylate polymer component. The phase separation modes depend on intermolecular interactions between small molecule TIPSE pentancene and polymer additives. The blend film with a dominant vertical phase separation exhibits a significant enhancement in average mobility and performance consistency of organic thin-film transistors. V

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