Flexible Indium‐Tin‐Oxide Homojunction Thin‐Film Transistors with Two In‐Plane Gates on Cellulose‐Nanofiber‐Soaked Papers

Flexible indium-tin-oxide (ITO)-based homojunction thin-film transistors (TFTs) are fabricated on cellulose-nanofiber-soaked paper substrates. The paper is simultaneously used as the gate dielectric and substrate. Source/drain electrodes and a channel layer are sputtered by one-step radio-frequency sputtering deposition. The paper exhibits a very large specific electric-double-layer capacitance of 2.3 mu F cm(-2) due to the existence of mobile protons. The flexible ITO-based TFTs can operate at a low voltage of 2.0 V and show a relatively high I-ON/I-OFF ratio of 7.5 x 10(6). Furthermore, no obvious electrical degradation is observed at various bending radii. Finally, inverter and NAND logic operation are demonstrated by the TFTs together with two in-plane gates. Such flexible homojunction TFTs on low-cost and biodegradable paper are promising for portable paper electronics.