Donal Bradley

Abstract:

Metal oxide thin-film transistors are increasingly used in the driving backplanes of organic light-emitting diode displays. Commercial devices currently rely on metal oxides processed via physical vapour deposition methods, but the use of solution-based processes could provide a simpler, higher-throughput approach that would be more cost effective. However, creating oxide transistors with high carrier mobility and bias-stable operation using such processes has proved challenging. Here we show that transistors with high electron mobility (50 cm2 V−1 s−1) and operational stability can be fabricated from solution-processed multilayer channels composed of ultrathin layers of indium oxide, zinc oxide nanoparticles, ozone-treated polystyrene and compact zinc oxide. Insertion of the ozone-treated polystyrene interlayer passivates electron traps in the channel and reduces bias-induced instability during continuous transistor operation over a period of 24 h and under a high electric-field flux density (2.1 × 10−6 C cm−2). Furthermore, incorporation of the pre-synthesized aluminium-doped zinc oxide nanoparticles enables controlled n-type doping of the hybrid channels, providing additional control over the operating characteristics of the transistors.

Abstract:

Managing the interference effects from thin (multi‐)layers allows for the control of the optical transmittance/reflectance of widely used and technologically significant structures such as antireflection coatings (ARCs) and distributed Bragg reflectors (DBRs). These rely on the destructive/constructive interference between incident, reflected, and transmitted radiation. While known for over a century and having been extremely well investigated, the emergence of printable and large‐area electronics brings a new emphasis: the development of materials capable of transferring well‐established ideas to a solution‐based production. Here, demonstrated is the solution‐fabrication of ARCs and DBRs utilizing alternating layers of commodity plastics and recently developed organic/inorganic hybrid materials comprised of poly(vinyl alcohol) (PVAl), cross‐linked with titanium oxide hydrates. Dip‐coated ARCs exhibit an 88% reduction in reflectance across the visible compared to uncoated glass, and fully solution‐coated DBRs provide a reflection of >99% across a 100 nm spectral band in the visible region. Detailed comparisons with transfermatrix methods (TMM) highlight their excellent optical quality including extremely low optical losses. Beneficially, when exposed to elevated temperatures, the hybrid material can display a notable, reproducible, and irreversible change in refractive index and film thickness while maintaining excellent optical performance allowing postdeposition tuning, e.g., for thermo‐responsive applications, including security features and product‐storage environment monitoring.