One-step printable platform for high-efficiency metasurfaces down to the deep-ultraviolet region

A single-step printable platform for ultraviolet(UV)metasurfaces is introduced to overcome both the scarcity of low-loss UV materials and manufacturing limitations of high cost and low throughput.By dispersing zirconium dioxide(ZrO_(2))nanoparticles in a UV-curable resin,ZrO_(2)nanoparticle-embedded-resin(nano-PER)is developed as a printable material which has a high refractive index and low extinction coefficient from near-UV to deep-UV.In ZrO_(2)nano-PER,the UV-curable resin enables direct pattern transfer and ZrO_(2)nanoparticles increase the refractive index of the composite while maintaining a large bandgap.With this concept,UV metasurfaces can be fabricated in a single step by nanoimprint lithography.As a proof of concept,UV metaholograms operating in near-UV and deep-UV are experimentally demonstrated with vivid and clear holographic images.The proposed method enables repeat and rapid manufacturing of UV metasurfaces,and thus will bring UV metasurfaces more close to real life.

Selectively patterned TiO2 nanorods as electron transport pathway for high performance perovskite solar cells

Organic-inorganic hybrid perovskite solar cells (PSCs) are attracting tremendous attention for new-generation photovoltaic devices because of their excellent power conversion efficiency and simple fabrication process. One of the various approaches to increase the efficiency of PSCs is to change the material or structure of the carrier transport layer. Here, optically long and electrically short structural concept is proposed to enhance the characteristics of a PSC by employing selectively grown single crystalline TiO2 nanorods. The approach has the merit of increasing the electro n-hole separati on effectively and en ables a thicker active layer to be coated without electrical loss by using TiO2 nano rods as an electr on pathway. Moreover, selectively grow n TiO2 nano rods in crease the optical path of the in cide nt light via scatteri ng effects and en able a smooth coati ng of the active layer. Nano imprint lithography and hydrothermal growth were employed to fabricate selectively grow n TiO2 nanorod substrates. The fabricated solar cell exhibits an efficiency of 19.86% with a current density, open-circuit voltage, and fill factor of 23.13 mA/cm^2, 1.120 V, and 76.69%, respectively. Time-resolved photoluminescence, ultraviolet-visible (UV-Vis) spectroscopy, and the incident phot on to current efficiency (IPCE) an alysis were conducted to understand the factors resp on sible for the improvement in characteristics of the fabricated PSCs.

Fabrication of perovskite solar cell with high short-circuit current density(Jsc)using moth-eye structure of SiOx

The performance of solar cells is determined by three factors:the open-circuit voltage(Voc),short-circuit current density(Jsc),and fill factor(FF).The Voc and FF are determined by the material bandgap and the series/shunt resistance,respectively.However,Jsc is determined by the amount of incident light in addition to the bandgap of the material.In this study,a moth-eye pattern was formed on a glass surface via direct printing to increase the amount of incident light and thus increase Jsc-The moth-eye pattern is a typical antireflection pattern that reduces the reflection by gradually increasing the refractive index.A flat perovskite solar cell(F-PSC)and a moth-eye patterned perovskite solar cell(M-PSC)had Jsc values of 23.70 and 25.50 mA/cm^2,respectively.The power-conversion efficiencies of the F-PSC and M-PSC were 19.81%and 21.77%,respectively.

Thermally-curable nanocomposite printing for the scalable manufacturing of dielectric metasurfaces

Metasurfaces consisting of artificially designed meta-atoms have been popularized recently due to their advantages of amplitude and phase of light control.However,the electron beam lithography method for metasurface fabrication has high cost and low throughput,which results in a limitation for the fabrication of metasurfaces.In this study,nanocomposite printing technology is used to fabricate high-efficiency metasurfaces with low cost.To demonstrate the efficiency of the proposed fabrication method,a metahologram is designed and fabricated using a nanocomposite.The metahologram exhibits conversion efficiencies of 48%and 35%at wavelengths of 532 and 635 nm,respectively.The nanocomposite is composed of polymers with nanoparticles,so durability tests are also performed to evaluate the effects of temperature and humidity on the metasurfaces.The test verifies that at temperatures below the glass transition temperature of the base resin,the nanostructures do not collapse,so the efficiency of the metasurfaces remains almost the same.The surrounding humidity does not affect the nanostructures at all.Hence,the durability of the nanocomposite metasurfaces can be further enhanced by replacing the base resin,and this nanocomposite printing method will facilitate practical metasurface use at low cost.