Bottom-Gate Complementary Inverters on Plastic With Gravure-Printed Dielectric and Semiconductors

Organic complementary circuitry combines all the advantages of plastic electronics, such as flexibility, thinness, and solution processability with low power consumption. Here, we report organic complimentary inverters fabricated in a carrier-free batch process on a plastic foil with dielectric and semiconductor layers patterned using the high-volume gravure contact printing technique. The transistor components have bottom-gate, bottom-contact configuration with aluminum gates and gold contacts, allowing full use of photolithographic processing while protecting the semiconductors by depositing them last. Cross-linkable polymer dielectric, p-type small molecule and n-type polymer semiconductors are printed from inks based on nonchlorinated solvents. Printing instability is observed for capillary numbers approaching 1. The 430-nm-thick dielectric affords a relatively low operational voltage, and it is the thinnest printed organic dielectric reported in the literature for organic inverters to date. Both p- and n-type transistors have a mobility of 0.01-0.04 cm²V^-1s^-1. The device parameters for the n-type transistors show less variation than the p-type transistors, which can be related to the more isotropic charge transport in polymer films compared with the small-molecule polycrystalline films. The resultant inverters have an average gain of 4.5 ± 1.5 and a maximum gain of 8 at V_DD = -20 V. The combination of the conventional photolithographic processing and gravure contact printing can therefore be used to fabricate bottom-gate organic complementary circuitry on plastic.