@article{83b817d591234773a8e8311cad475ef3,
title = "Solution processes for ultrabroadband and omnidirectional graded-index glass lenses with near-zero reflectivity in high concentration photovoltaics",
abstract = "Concentrator photovoltaic (CPV) systems, where incident direct solar radiation is tightly concentrated onto high-efficiency multi-junction solar cells by geometric optical elements, exhibit the highest efficiencies in converting the sun{\textquoteright}s energy into electric power. Their energy conversion efficiencies are greatly limited, however, due to Fresnel reflection losses occurring at three air/optics interfaces in the most sophisticated dual-stage CPV platforms. This paper describes a facile one-step wet-etching process to create a nanoporous surface with a graded-index profile on both flat and curved glasses, with capabilities of achieving ~99% average transmission efficiency in a wide wavelength range from 380 nm to 1.3 µm and for a wide range of incident angles up to ±40° regardless of the polarization state of incident sunlight. The simplicity of the etching process remarkably increases their versatility in various optical elements that require unconventional form factors such as Fresnel lenses and microlens arrays, and/or demanding curvatures along with much reduced dimensions such as ball lenses. Etched glass surfaces on two-stage optical concentrating systems yield enhancements in total optical transmission efficiencies by 13.8% and in the photocurrent by 14.3%, as experimentally determined by measurements on microscale triple-junction solar cells. The presented strategy can be widely adapted in a variety of applications such as image sensors, display systems, and other optoelectronic devices.",
author = "Junwen He and Yuan Yao and Lee, {Kyu Tae} and Nina Hong and Brent Fisher and Bahabry, {Rabab R.} and Lee, {Jung Woo} and Jeonghyun Kim and Seungyong Han and Kalidindi, {Sanjay V.} and Kim, {Jae Hwan} and Kim, {Sung Bong} and Jaewon Choi and Hongwoo Jang and Myeong Namkoong and Scott Burroughs and Muhammad Hussain and Nuzzo, {Ralph G.} and Rogers, {John A.}",
note = "Funding Information: This work is part of the {\textquoteleft}Light-Material Interactions in Energy Conversion{\textquoteright} Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001293. This work was also supported in part by the Ministry of Trade, Industry and Energy (MOTIE, No. 10051565) and Korea Display Research Corporation (KDRC) support program for the development of future devices technology for display industry. This work was also supported by Pusan National University Research Grant, 2017. J.K. gratefully acknowledges the support from the Research Grant of Kwangwoon University in 2018. S.H. was supported by the new faculty research fund of Ajou University and the Ajou university research fund. The authors thank K. Walsh, R. Haasch and H. Zhou in UIUC for their assistance with materials characterization and J. VanDerslice at J. A. Woollam Co. for helpful discussions on the EEP results. Publisher Copyright: {\textcopyright} 2018, The Author(s).",
year = "2018",
month = dec,
day = "1",
doi = "10.1038/s41598-018-33200-9",
language = "English (US)",
volume = "8",
journal = "Scientific Reports",
issn = "2045-2322",
publisher = "Nature Publishing Group",
number = "1",
}