Flexible nanograss with highest combination of transparency and haze for optoelectronic plastic substrates

Abstract

Transparent polymer substrates have recently received increased attention for various flexible optoelectronic devices. Optoelectronic applications such as solar cells and light emitting-diodes would benefit from substrates with both high transparency and high haze, which increase how much light scatters into or out of the underlying photoactive layers. In this letter, we demonstrate a new flexible nanograss plastic substrate that displays the highest combination of transparency and haze in the literature for polyethylene terephthalate (PET). As opposed to other nanostructures that increase haze at the expense of transparency, our nanograss demonstrates the potential to improve both haze and transparency. Furthermore, the monolithic nanograss may be fabricated in a facile scalable maskless reactive ion etching process without the need for additional lithography or synthesis of nanostructures. Our 9 μm height nanograss sample exhibits a transparency and haze of 92.4% and 89.4%, respectively, and our 34 μm height nanograss displays a transparency and haze of 91.0% and 97.1%, respectively. We also performed durability experiments that demonstrate these nanostructured PET substrates are robust from bending and show similar transmission and haze values after 5000 cycles of bending.

Challenges and Prospects of Bio-Inspired and Multifunctional Transparent Substrates and Barrier Layers for Optoelectronics

“…71 (b) (i) Nanograss glass with 1 and without 8 OTS coating, as well as the aggregated alumina nanowire arrays on glass 122 and imprinted PDMS on glass. 123 (c) (i) Nanograss PET, 7 as well as plastic−paper, 71 silica nanoparticle array on PET, 124 and doped poly(methyl methacrylate) (PMMA)/poly(ethylene terephthalate) (PET) without 125 and with shear. 126 transparent paper based on wood fibers, with ultrahigh transparency of ≈96% as well as high optical haze (≈60%).…”

“…We have reported the fabrication of high transparency, high haze flexible plastics. 7 Figure 5c(i) shows the optical performance of the best plastic substrates reported in the literature (gray markers) as well as the performance of our high transparency high haze plastic substrates, plotted with green circles. The literature data plotted includes plastic−papers, 71 poly(ethylene terephthalate) (PET) coated with silica nanoparticles, 124 and doped poly-(methyl methacrylate) (PMMA)/PET without 125 and with shear.…”

“…Figure 5c shows (ii) optical and (iii) SEM images of our high transparency and high haze plastic. 7 WETTING PROPERTIES AND MULTIFUNCTIONAL SURFACES A variety of functionalities are desirable for optoelectronic substrates and barrier films related to maintaining their optical properties after exposure to various liquids or particulates. These functionalities are often closely correlated to the wetting properties of the surface and include antisoiling, self-cleaning, stain resistance, antifogging, and anti-icing.…”

“…Surfaces in nature such as the moth eye, wings of cicada, and glasswing butterfly wing provide bio-inspiration. Micro/nanostructures provide controlled optical properties such as light scattering , and tunable wetting properties . Multifunctional optoelectronic substrates and barrier layers can be used in many devices such as smart phones, e-paper, solar modules, and flexible devices.…”

An Intrinsically Micro‐/Nanostructured Pollen Substrate with Tunable Optical Properties for Optoelectronic Applications

“…[ 8–12 ] Within this scope, synthetic polymers such as poly(ethylene terephthalate) (PET), polyimide (PI), polyurethane (PU), and poly(dimethylsiloxane) (PDMS) are widely used as flexible substrates for inorganic, organic, and perovskite solar cells due to the ability to finetune material properties along with low cost, high flexibility, and optical transparency. [ 13–22 ]…”