Ultrahigh Transparency, Ultrahigh Haze Nanograss Glass with Fluid-Induced Switchable Haze

Optoelectronic applications such as solar cells and light emitting diodes would benefit from glass substrates with both high transparency and high haze to improve power conversion and extraction efficiencies, respectively. In this letter, we demonstrate a new nanograss fused silica glass that displays ultrahigh transparency and ultrahigh haze (both over 95% at wavelength 550 nm). The nanograss may be fabricated through a scalable maskless reactive ion etching (RIE) process in fused silica where the height may be controlled through the etch time. We demonstrate that shorter nanograss (< 2.5 um height) improves the antireflection properties of the glass, and that longer grass tends to increase haze monotonically. Ultrahigh haze over 99% may also be achieved with longer nanograss (> 6 um), though the transmission decreases slightly to less than 92% at such ultrahigh haze. Finally, we demonstrate that various fluids with a similar index of refraction as the glass may be utilized to permeate the superhydrophilic hazy nanograss, such that it resembles a uniform flat glass substrate with little haze. Upon removal of this fluid, the nanograss recovers its original hazy state. This haze switchability may have application in various smart glass.