(Invited) Patterning Transparent and Antireflective Compound Semiconductor Oxide Thin Films and Nanowire Networks from Solution

Abstract

New types of transparent conducting materials (TCMs) are being sought due to the increase in demand for their use in next generation electronics and photonics. Methods to improve transparency be inferred by controlling porosity (graded refractive index), or from a change in the crystal structure of some materials that are not inherently transparent at visible frequencies. Transparent materials with tunable optical properties are important in conductive and capacitive displays, tandem solar cells, organic PVs and other devices. Transparent conducting oxides (TCO) have been extensively used in various technologically important applications including solar cells, flat panel displays, antireflective coatings, (organic)light emitting diodes and many other uses as advanced optical materials. Nanoporous and nanostructured films, assemblies and arrangements are important from an applied point of view in microelectronics, photonics and optical materials. The ability to minimize reflection, control light output and use contrast and variation of the refractive index to modify photonic characteristics can provide routes to enhanced photonic crystal devices, omnidirectional reflectors, antireflection coatings and broadband absorbing or reflecting materials. Here, we detail how interdiffusion processes can be used to modify the crystallinity and phase of solution processed semiconducting oxides, to dielectric complex oxides on glass as thin films or as oxide nanowire networks. In addition, we demonstrate how electrodeposition of mobile ionic species on TCOs and SiO2/Si can allow this process to happen from a top down process, enabling patterned optically transparent coatings with in-plane semiconductor-dielectric contrast. Last, we show how these processes can allow networks of oxide nanowire to form directly from solution processed oxide thin films on a range of substrate types. Antireflective properties and the onset of broadband transparency for interdiffusion-mediated oxide conversion processes are also shown. References M. Eliason and M. D. Shawkey, Opt. Express, 22, A642 (2014).C. Glynn and C. O'Dwyer, Adv. Mater. Interfaces, 4, 1600610 (2017).C. O’Dwyer, M. Szachowicz, G. Visimberga, V. Lavayen, S. B. Newcomb and C. M. S. Torres, Nature Nanotechology, 4, 239 (2009).Q. Xi, M. F. Schubert, J. K. Kim, E. F. Schubert, M. Chen, S. Y. Lin, W. Liu and J. A. Smart, Nature Photonics, 1, 176 (2007).C. O'Dwyer and C. M. S. Torres, Front. Physics, 1, 18 (2013).C. Glynn, D. Creedon, H. Geaney, J. O'Connell, J. D. Holmes and C. O'Dwyer, ACS Appl. Mater. Interfaces, 6, 2031 (2014).K. Banger, Y. Yamashita, K. Mori, R. L. Peterson, T. Leedham, J. Rickard and H. Sirringhaus, Nature Materials, 10, 45 (2011).C. Glynn, D. Creedon, H. Geaney, T. Collins, E. Armstrong, M. A. Morris and C. O'Dwyer, Sci. Rep., 5, 11574 (2015).C. Glynn, D. Aureau, G. Collins, S. O'Hanlon, A. Etcheberry and C. O'Dwyer, Nanoscale, 7, 20227 (2015).C. Glynn, H. Geaney, D. McNulty, J. O'Connell, J. D. Holmes and C. O’Dwyer, J. Vac. Sci. Technol. A, 35, 020602 (2017).C. Glynn, L. Balobaid, D. McNulty and C. O’Dwyer, ECS J. Solid State Sci. Technol., 6 (2017).