Controlled solution deposition and systematic study of charge-transport anisotropy in single crystal and single-crystal textured TIPS pentacene thin films

摘要

In this work, bis-(triisopropylsilylethynyl) pentacene (TIPS pentacene) films were fabricated with a newly designed system for controlled solution casting with adjustable nitrogen flow and deposition temperature, which consequently enabled a systematic examination of crystal orientation-dependent mobilities in single crystal and single-crystal textured TIPS pentacene transistors. One of the two n-n stacking directions in TIPS pentacene films was found to be close to [210] (or the long axis of needle-shaped TIPS pentacene films), with frequent twinning observed between crystalline domains across the (120) planes that are the lateral facets for individual crystallites. The [210] axes of crystalline TIPS pentacene thin films ran across source-drain channels at different angles, showing a ten-fold hole mobility increase as the [210] crystallographic axis became parallel to the channel direction. Our results also suggest that the controlled solution casting may be a promising method in fabricating solution-processible small-molecule organic semiconductors with varied morphologies.