Influence of substrate temperature and overlap condition on the evaporation behavior of inkjet-printed semiconductor layers in organic thin film transistors

• Crystal structure of inkjet-printed semiconductor layers was controlled.
• Crystal growth is determined by evaporation behavior of drying semiconductor layers.
• The evaporation behavior is affected by overlap condition and substrate temperature.
• Well-oriented crystal structure can be obtained by uniform contact line movement.
• OTFTs with well-oriented crystal structures show good electrical performance.

In this study, we investigate the evaporation behavior of inkjet-printed semiconductor layers of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) to obtain well-oriented crystalline structures for the fabrication of high-performance organic thin film transistors (OTFTs). Variations in overlap and substrate temperature are considered to control the evaporation behavior and the resulting crystalline structures of the layers. The internal flow and corresponding contact line movement can be controlled via three representative inkjet-printing regimes. For inkjet-printing regimes that induce outward convective flow (the coffee stain effect), randomly-oriented TIPS pentacene crystalline structures are produced by irregular contact line receding. With an optimized inkjet-printing regime, uniform bottom contact line movement is generated by the unidirectional internal flow, resulting in well-oriented crystalline structures. All-inkjet-printed OTFTs with semiconductor layers inkjet-printed using the optimized regime exhibit a high field effect mobility of ~ 0.13 cm2/Vs, due to the one-dimensionally-oriented TIPS pentacene crystal arrays.