Optimization of Inkjet-Printed 6,13-Bis(triisopropylsilylethynyl) pentacene Using Photolithography-Defined Structures

In this work, the performance of inkjet-printed 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)-based organic thin-film transistors (OTFTs) was studied under various printing conditions using photolithography-defined test structures. OTFTs were printed from TIPS-pentacene solutions with several concentrations, and the impact of printing temperature as well as the amount of material printed was studied. A hybrid approach that includes wells defined by a photolithography process and printed TIPS solution is demonstrated. The results show that the mobility of the printed OTFTs increases with increasing solution concentration, with a maximum mobility for concentration of 50 mg/mL and substrate temperature of 50°C. X-ray diffraction analysis showed the presence of the thin-film phase for all of the TIPS concentrations, with strong and sharp preferential orientation along the (001) direction without any disruption in molecular packing with increasing TIPS thickness. Optimized OTFTs fabricated with this technique show mobilities of 5 × 10⁻² cm²/V-s, threshold voltages (V_T) in the range of −5 V, and subthreshold slopes of approximately 0.5 V/dec. On–off current ratios up to 10⁶ were also achieved.