Flexible Oxide Thin Film Transistor With Nanocellulose As Gate Dielectric

Flexible electronics are attracting more and more attention for their outstanding features,such as light weight,excellent mechanical flexibility,and shock resistance.As an important element in the display field,flexible oxide thin-film transistors the advantages of higher mobility,better flexibility,and low-temperature preparation.With the in-depth study of flexible thin film transistors,flexible display products have gradually appeared in people's daily lives.For flexible thin-film transistors,the choices of substrates are particularly important.Among many flexible materials,cellulose papers stands out for their recyclable,cheap and biodegradable properties.Although the performance of paper-based transistors have been significantly improved,the problems of paper substrates,such as high roughness,complicated manufacturing processes,and large operating voltages,still need to be solved.In recent years,nanocellulose has attracted much attention due to its strong mechanical strength and excellent flexibility.The internal composition diameter of paper based nanocellulose is much smaller than that of ordinary paper.It is reported that thin film transistors with nanocellulose as the gate dielectric can induce high-density carriers in the channel layer at a lower gate voltage due to the electric-double-layer?EDL?electrostatic coupling.This paper mainly studies the flexible double-layer thin film transistor based on nanocellulose.First,the electrical properties of nanocellulose are characterized by Ag/Cellulose-nanofibers/Ag structure,which exhibits large double-layer capacitance and small leakage current.Then,the nanocellulose solution is added to the paper coated with the Ag layer.After drying at low temperature to form a film,the source/drain electrode and channel layer are sputtered on the nanocellulose film by radio-frequency sputtering deposition.Such transistors can operate at a lower voltage and show better electrical properties,with a field-effect mobility of 4.15 cm²V^-1s^-1,indicating that nanocellulose is an excellent gate dielectric.Then,the nanocellulose solution is used to improve the pore structure of ordinary paper.The nanocellulose paper is simultaneously used as the gate dielectric and substrate.ITO is deposited as source/drain electrodes and channel layer by a one-step sputtering deposition.Due to the presence of mobile protons,the paper has a large electric-double-layer specific capacitance of 2.3?F/cm².Such devices can operate at low voltages of 2.0 V and show a high I_OFF/I_ON ratio of 7.5×10⁶and the field-effect mobility of 7.8 cm²V^-1s^-1.In addition,the transistors show good mechanical stability,environmental stability,and bias stability.Finally,the logic operation of the inverter and NAND is demonstrated using the double-side gate structure of such thin film transistors.In summary,the two types of low-voltage flexible thin film transistors based on nanocellulose show good electrical properties.This paper explores the possibility of nanocellulose in flexible electronics.The flexible TFTs on low-cost,biodegradable paper are promising for the development of portable electronic products.