Controllably Aligned Ultra-Flexible and High-Performance Organic Single-Crystal Arrays Via Solvent Vapor Annealing for Large Area Soft Electronics

Abstract

Recently, semiconducting organic materials have been actively investigated for achieving high performance organic thin-film transistors and applying to diverse electronic applications. Particu-larly, in order to control the location and direction of organic single crystals with a densely packed molecular structure, several techniques such as inkjet printing and sheared deposition us-ing a self-assembled mono-layer pattern have been suggested. In this presentation, we used sol-vent vapor anneal (SVA) process of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) organic films, forming diverse patterns of their organic single crystals. Room-temperature photochemical patterning of polymer dielectric layer by using deep ultraviolet (DUV) enables the determined organization of C8-BTBBT single crystals with controlled-position and orientation. In SMSVA process, C8-BTBT small molecules become mobile on soluble polymer layer and re-assembled into micro rod-shaped single crystal only at pristine polymer dielectric region. Using the novel SVA, C8-BTBT single crystal arrays were easily produced on narrow trench of pristine polymer dielectric while their diverse patterns such as a multi-lines, zigzags and star shape were readily possible as well. Based on these arrays of C8-BTBT single crystals, we fabricated high performance and large current organic single crystal transistor on a 3-μm-thick flexible film in which the saturation mobility of devices exceeds ~ 3 cm2 V-1s-1 for one single crystal micro-rod. It was also found that the high performance of single crystal transistor remained functional following the aggressive bending test. We rolled up the device on optical fiber (bending radius:150 μm). After the bending test, the devices show reliable performance without significant degradation from its initial characteristics.