A growing number of commercial products such as displays, solar panels, light emitting diodes (LEDs and OLEDs),
automotive and architectural glass are driving demand for glass with high performance surfaces that offer anti-reflective,
self-cleaning, and other advanced functions. State-of-the-art coatings do not meet the desired performance characteristics
or cannot be applied over large areas in a cost-effective manner. “Rolling Mask Lithography” (RML™) enables highresolution
lithographic nano-patterning over large-areas at low-cost and high-throughput. RML is a photolithographic
process performed using ultraviolet (UV) illumination transmitted through a soft cylindrical mask as it rolls across a
substrate. Subsequent transfer of photoresist patterns into the substrate is achieved using an etching process, which
creates a nanostructured surface. The current generation exposure tool is capable of patterning one-meter long substrates
with a width of 300 mm. High-throughput and low-cost are achieved using continuous exposure of the resist by the
Here, we report on significant improvements in the application of RML™ to fabricate anti-reflective surfaces. Briefly,
an optical surface can be made antireflective by “texturing” it with a nano-scale pattern to reduce the discontinuity in the
index of refraction between the air and the bulk optical material. An array of cones, similar to the structure of a moth’s
eye, performs this way. Substrates are patterned using RML™ and etched to produce an array of cones with an aspect
ratio of 3:1, which decreases the reflectivity below 0.1%.
Using a dense organic monolayer, self-assembled and directly bound to n-Si, as high quality insulator with a thickness that can be varied from 1.5-2.5 nm, we construct a Metal-Organic Insulator-Semiconductor (MOIS) structure, which, if fabricated with semi-transparent top electrode, performs as a hybrid organic-inorganic photovoltaic device. The feasibility of the concept and the electrical properties of the insulating layer were first shown with a Hg top electrode, allowing use of prior know-how from electron transport through molecular monolayers, but with photon collection only from around the electrode. We then used another bottom-up fabrication technique, in addition to molecular self-assembly, electro-less metal deposition, to implement an all-covalently bound solid state device. Electro-less Au deposition yields an electrically continuous, porous and semi-transparent top electrode, improving photon harvesting. Aside from being a nearly ideal insulator, the monolayer acts to passivate and protect the interfacial Si layer from defects and to decrease the surface state density. In addition the cell, like any MIS solar cell, benefits from that the light needs only to cross a few thin transparent layers (anti-reflective coating, organic insulator) to reach the photovoltaically active cell part. This helps to generate carriers close to the junction area, even by short wavelength photons, and, thus, to increase light collection, compared to p-n junction solar cells. Due to low temperature cell fabrication without high vacuum steps, the MOIS approach might be interesting for low cost solar cells.