Spatial Mapping of Morphology and Electronic Properties of Air-Printed Pentacene Thin Films

Abstract

To accelerate the pace of materials discovery and application, comprehensive links need to be established between a material's structure, properties, and process conditions used to obtain the material and/or final application format. This work examines the dry printing of pentacene thin film transistor (TFT) channels by guard flow-enhanced organic vapor jet printing (GF-OVJP), a technique that enables direct, solvent-free, additive patterning of device-quality molecular semiconductors in air. Deposition in air entails non-trivial effects at the boundary between ambient surroundings and the gas jet carrying the semiconductor vapor that influence the morphology and properties of the resulting electronic devices. Synchrotron X-ray diffraction is employed, complemented by measurement of electronic properties of GF-OVJP deposited films in a TFT to reveal how the morphology and electronic properties of the films depend on thickness, location within the printed pattern, nozzle translation velocity, and other process parameters. The hole field-effect mobility of the printed pentacene film is linked quantitatively with its crystallinity, as well as with extent of exposure to ambient air during deposition. The analysis can be extended to accurately predict the performance of devices deposited in air by GF-OVJP, which are demonstrated here for a planar, large area deposit.