Effect of Crystallization Modes in TIPS-pentacene/Insulating Polymer Blends on the Gas Sensing Properties of Organic Field-Effect Transistors

Jung Hun Lee, Yena Seo, Yeong Don Park, John E. Anthony, Do Hun Kwak, Jung Ah Lim, Sunglim Ko, Ho Won Jang, Kilwon Cho, Wi Hyoung Lee
2019 Scientific Reports  
See next page for additional authors Right click to open a feedback form in a new tab to let us know how this document benefits you. Blending organic semiconductors with insulating polymers has been known to be an effective way to overcome the disadvantages of single-component organic semiconductors for high-performance organic field-effect transistors (OFETs). We show that when a solution processable organic semiconductor (6,13-bis(triisopropylsilylethynyl)pentacene, TIPS-pentacene) is blended
more » ... with an insulating polymer (PS), morphological and structural characteristics of the blend films could be significantly influenced by the processing conditions like the spin coating time. Although vertical phaseseparated structures (TIPS-pentacene-top/PS-bottom) were formed on the substrate regardless of the spin coating time, the spin time governed the growth mode of the TIPS-pentacene molecules that phase-separated and crystallized on the insulating polymer. Excess residual solvent in samples spun for a short duration induces a convective flow in the drying droplet, thereby leading to one-dimensional (1D) growth mode of TIPS-pentacene crystals. In contrast, after an appropriate spin-coating time, an optimum amount of the residual solvent in the film led to two-dimensional (2D) growth mode of TIPSpentacene crystals. The 2D spherulites of TIPS-pentacene are extremely advantageous for improving the field-effect mobility of FETs compared to needle-like 1D structures, because of the high surface coverage of crystals with a unique continuous film structure. In addition, the porous structure observed in the 2D crystalline film allows gas molecules to easily penetrate into the channel region, thereby improving the gas sensing properties. Organic field-effect transistors (OFETs) based on solution-processable conjugated small molecules or polymers are widely investigated owing to their popular application as components in electronic devices such as flexible displays, sensors, radio frequency identification tags, and logic circuits 1-5 . However, solution processing of small molecule semiconductors often poses certain problems: their strong π-π interactions induce non-uniform morphologies and dewetting of their films from the substrate, resulting in poor electrical performance of the devices 6,7 . In attempts to overcome these problems, the small-molecular semiconductors were blended with insulating polymers that have excellent film-forming properties and OFETs based on the films of such blends have been fabricated using various approaches 7-9 . Blending small-molecular semiconductors with insulating polymers effectively improves their processability, facilitates environmental stability of OFETs designed based on them, and Published: xx xx xxxx OPEN www.nature.com/scientificreports/
doi:10.1038/s41598-018-36652-1 fatcat:cjqm34fn6ngojmxdzuw2ah4d2e