Cellulose Nanocrystal Aqueous Inks Evaluated for Printed Electronics and Application to Thin-film Transistors
With increasing demand for smart features on consumer items, it is imperative that a new class of environmentally sustainable processing methods and materials are developed in order to enable smart functionality on mass produced goods. We have demonstrated significant first steps towards this goal through development of conductive, aqueous-based inks of nanocrystalline cellulose (CNC) for low-waste additive processing via inkjet printing. Aqueous CNC solutions were tuned for printability through addition of ethanol and ethylene glycol before successful patterning unto amorphous silicon (a-Si:H) thin-film transistors (TFTs) as proof-of-concept source and drain contacts. Bio-mass-sourced CNC nanoparticles functionalized with conductive polypyrrole polymer (CNC-PVP-PPY) were found to withstand temperatures of 150°C and displayed conductivity as high as 77.8 S-m-1. Two key observations were made: TFTs fabricated with printed CNC-PVP-PPY contacts successfully showed switching behaviour with typical mobilities on the order of 0.2 cm2V-1s-1, on-off ratio of 106, threshold voltage of 7.6V, and subthreshold swing of 264 mV/dec, however, the larger contact resistance for CNC-PVP-PPY had an impact on the extracted parameters when compared to sputtered metal and printed annealed-silver nanoparticle contact devices. This is the first reported instance of conductive CNC nanoparticles successfully print-processed from aqueous inks and integrated into TFTs.