Integrating biodegradable cellulose nanopaper into oxide thin-film transistors (TFTs) for next generation flexible and green flat panel displays has attracted great interest because it offers a viable solution to address the rapid increase of electronic waste that poses a growing ecological problem. However, a compromise between device performance and thermal annealing remains an obstacle for achieving high-performance nanopaper TFTs. In this study, a high-performance bottom-gate IGZO/Al2O3 TFT with a dual-layer channel structure was initially fabricated on a highly transparent, clear, and ultrasmooth nanopaper substrate via conventional physical vapor deposition approaches, without further thermal annealing processing. Purified nanofibrillated cellulose with a width of approximately 3.7 nm was used to prepare nanopaper with excellent optical properties (92% transparency, 0.85% transmission haze) and superior surface roughness (Rq is 1.8 nm over a 5 × 5 μm2 scanning area). More significantly, a bilayer channel structure (IGZO/Al2O3) was adopted to fabricate high performance TFT on this nanopaper substrate without thermal annealing and the device exhibits a saturation mobility of 15.8 cm2/(Vs), an Ion/Ioff ratio of 4.4 × 105, a threshold voltage (Vth) of -0.42 V, and a subthreshold swing (SS) of 0.66 V/dec. The room-temperature fabrication of high-performance IGZO/Al2O3 TFTs on such nanopaper substrate without thermal annealing treatment brings industry a step closer to realizing inexpensive, flexible, lightweight, and green paper displays.
Keywords: IGZO semiconductor; cellulose nanofiber nanopaper; electrical properties; thin-film transistor; ultrasmooth.