Ultra‐Flexible, “Invisible” Thin‐Film Transistors Enabled by Amorphous Metal Oxide/Polymer Channel Layer Blends

Abstract

Ultra-flexible and transparent metal oxide transistors are developed by doping In2 O3 films with poly(vinylphenole) (PVP). By adjusting the In2 O3 :PVP weight ratio, crystallization is frustrated, and conducting pathways for efficient charge transport are maintained. In2 O3 :5%PVP-based transistors exhibit mobilities approaching 11 cm(2) V(-1) s(-1) before, and retain up to ca. 90% performance after 100 bending/relaxing cycles at a radius of 10 mm.

Metal oxide semiconductor thin-film transistors for flexible electronics

“…29,115 Alternatives to Ga doping in IZO have also been developed, using tin (Sn), hafnium (Hf), and zirconium (Zr 76 including neat layers, nanoparticle (NP), or nanowire (NW) films, as well as blends of In 2 O 3 and polyvinylpyrrolidon (PVP). 76,145,[190][191][192] 83 either in the form of neat IGZO or in blends of IGZO and graphene nanosheets. 83,200,201 B.…”

Flexography‐Printed In2O3 Semiconductor Layers for High‐Mobility Thin‐Film Transistors on Flexible Plastic Substrate

“…[ 10 ] Recently, the maximum temperature for retaining the amorphous phase of In 2 O 3 has been extended with mixing In-precursor with poly(4-vinylphenol) (PVP) polymers. [ 11 ] Since the roughness of the top surface of the In 2 O 3 layer is reducing with increasing amount of layers, we do not expect a notable increase in average diameter of the nanocrystals with increasing semiconductor thickness. Active research on identifi cation of the effect of different processing conditions, interfaces and precursor materials on the formation of either nanocrystalline or amorphous In 2 O 3 thin fi lm is required but is, however, outside the scope of this article.…”

“…Thermally evaporated thin polycrystalline In 2 O 3 TFTs have been shown to exhibit a strongly thickness-dependent mobility in the 5-20 nm thickness range which could amplify a small variation in semiconductor thickness into large variation in device mobility. [ 38 ] In this scenario, the observed spread in device mobility could be improved by suppressing In 2 O 3 crystallization for obtaining more homogenous amorphous phase via conventional Ga/Zn-doping or via PVP, [ 2,3,11 ] or by further optimization of the printing process for low variation in fi lm thickness of the nanocrystalline In 2 O 3 . The incremental mobility for two and three layer devices measured at the linear regime at drain voltage V D = 1 V (see Figure S7a,b, Supporting Information) is monotonously increasing with gate voltage V G from V on up to 20 V, which indicates that the devices operate at the trap-fi lling-limited mobility regime rather than in the regime where mobility is limited by semiconductor-dielectric interface scattering.…”

“…A large amount of work has concentrated on lowering the conversion temperature of the precursor solutions to semiconducting metal-oxide layers. Functional TFTs have been obtained at ≈200 °C or below (1) via the careful design of precursor chemistry utilizing metal alkoxides with controlled hydrolysis, [ 14,15 ] combustion process, [ 11,19 ] or the addition of oxidizing agents, [ 20 ] (2) via the use of additional energy in conversion such as various wavelengths of UV light, [ 8,15,21 ] or microwaves, [ 22 ] or (3) by employing conditions during annealing that promote effi cient precursor conversion such as ozone or vacuum. [ 6,7,20 ] After the fi rst report on inkjet-printed metal oxide layers from metal chloride precursors by Lee et al in 2007, [ 16 ] the deposition of metal-oxide semiconductor layers for TFTs has been successfully performed via several printing techniques.…”

“…[ 2,3 ] Although undoped In 2 O 3 possess high bulk charge-carrier concentration limiting its usability as semiconductor channel, thin (≈10 nm) In 2 O 3 semiconductor layers have recently been successfully utilized as semiconductor layers for high-mobility solution-processed TFTs, albeit in some cases with nonoptimal depletion-mode operation. [6][7][8][9][10][11][12] Metal-oxide semiconductor layers can be solution processed from stabilized nanoparticle dispersions or from sol-gel-precursor solutions. [ 3,4 ] Nanoparticles typically require high temperature sintering (>400 °C) to allow a connected network of particles and to remove dispersion stabilizing encapsulants.…”