An organic thin-film transistor with photolithographically patterned top contacts and active layer

The organic thin film transistor (OTFT) fabrication process has labored under a constraint related to the source/drain contacts, which can be formed either above or below the active layer, referred to, respectively, as top and bottom contact geometries. The top contact geometry is known to provide better performance, e.g., higher field-effect mobilities, but until now only the bottom contact geometry has been compatible with a high level of integration, since the top contact geometry requires patterning of the source/drain metal on top of the organic semiconductor, which can be strongly degraded by typical solvents, rendering it incompatible with photoresist and developers. In this paper, we describe a simple process for simultaneously patterning OTFT top contacts and active layer by photolithography. This is the first report of OTFTs with photolithographically patterned top contacts. The new process closes the gap between the high performance achievable from single devices and that of highly integrated devices.