Self-assembled monolayers induced performance difference in organic single crystal field-effect transistors

Abstract

Abstract In this report, 2,7-bis(4-methoxyphenyl)[1]benzothieno [3,2-b][1]benzothiophene. (DBOP-BTBT) organic single crystal field-effect transistors (OSCFETs) based on octyltrichlorosilane (OTS) and hexamethyldisilazane (HMDS) treated substrates have been systematically investigated. During all three consecutive scans of all transistors with different orientation in a-b plane, transistors modified with HMDS exhibit negligible hysteresis, while those modified with OTS show large hysteresis. Meanwhile, a high mobility up to 12.9 cm2 V-1 s-1 is obtianed for HMDS devices, compared to 7.7 cm2V-1 s-1 for devices modified with OTS. The hysteresis difference can be explained by the different trap densities between forward scan and reverse scan. Furthermore, the discrepancy in mobilities of forward and reverse scans is interpreted using a scattering model. Finally, after comparing the surface energies HMDS and OTS treated substrates, we attribute the performance difference between HMDS and OTS modified devices to the difference in intermolecular interaction between the SAMs and water. The work here indicates the importance of fine selection of SAMs for OSCFETs.