Formation of highly crystalline organic semiconductor thin films by inkjet printed thickness gradients

Highly crystalline organic semiconductor layers patterned from a solution was inkjet printed for the fabrication of TFTs. A novel printing process enabled the micro-scale control of the film formation through the use of precision spatial placement of printed droplets over the device structure. The printing process used temporal and spatial control of the printed droplets to form a crystallization gradient. The gradient, first nucleated over an electrode that defines the TFT structure is used to recrystallize subsequently printed droplets; the initial printed film was then used to recrystallize subsequent printed regions as the channel region is deposited along the channel length. This printed gradient provides a larger grain structure to form within the active region of the TFT. Furthermore, by controlling the fluid dynamics through drying of the printed droplets, the film thickness profiles could be controlled within a specific region where the semiconductor crystallinity was enhanced