Control of the molecular order and cracks of the 6,13- bis(triisopropylsilylethynyl)-pentacene on a polymeric insulator by anisotropic solvent drying

We describe a control scheme of the molecular order and cracks in a solution-processed 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) film on a polymeric insulator by the anisotropic temperature-gradient in the process of solvent drying. The solvent for TIPS-pentacene sequentially evaporates from the high temperature region to the low temperature region. As a result, the elongated domains of TIPS-pentacene molecules are developed along the temperature-gradient direction. As increasing of temperature-gradient, TIPS-pentacene molecules tend to be more ordered, which facilitates intramolecular charge transport. Consequently, it is found that the mobility increases and reaches about 0.4 cm²/Vs in an organic thin-film transistor fabricated with the TIPS-pentacene film prepared at the condition of room temperature -90 C. Comparing with 0.1 cm²/Vs for the case of a conventional solvent drying method, the mobility is enhanced about four-times. On further increasing of temperature-gradient, however, the crack begins to develop at the higher temperature region toward the lower temperature region, and the corresponding mobility decreases drastically. This indicates that there is a trade-off between the enhancement of the molecular order and the generation of the cracks of a solution-processed organic semiconductor prepared by anisotropic solvent drying.