Ultra-Antireflective Electrodeposited Plasmonic and PEDOT Nanocone Array Surfaces

Abstract

International audienceNovel broadband ultra-antireflective surfaces were created via the electrodeposition of a nanostructured zinc oxide thin film onto conductive, light absorbing periodic nanocone arrays. Nanocone arrays of (i) fluorinated ethylene propylene (FEP) coated with a 50 nm plasmonic gold thin film and (ii) the electroactive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) exhibited a very low broadband reflectivity of less than 0.1% from 475 to 800 nm at a wide range of incident angles after the electrodeposition of a nanostructured ZnO thin film onto the surface. SEM images reveal the formation of ZnO nanoflowers and nanorods on both nanocone array surfaces; these additional ZnO nanostructures enhance the coupling of the incident visible light into the absorptive gold or PEDOT nanocones to significantly reduce the reflectivity of these surfaces. The ZnO-coated nanocone array surfaces also exhibited an enhanced photoreactivity for the oxidative degradation of methylene blue, suggesting their potential to be used as a self-cleaning antireflective surface

Quantitative Characterization of Optical Coupling in Nanoporous ZnO–WO3 and ZnO–PEDOT Composite Electrodeposited Gratings Using Electrodiffraction Measurements

“…In these gratings, the ZnO enhances the delivery of light to the underlying electrochromic materials via optical coupling. We have also observed this coupling effect previously in the enhanced antireflectivity of PEDOT and gold nanocone arrays that were coated with electrodeposited ZnO nanostructures . Going forward, we should be able to employ this coupling effect to enhance the production of electron–hole pairs by enhancing the optical absorption of TiO 2 , In 2 O 3 , or Si semiconductor patterned gratings, nanocone arrays, or nanoring arrays.…”

“…For example, its wide band gap (3.37 eV) has made ZnO a popular semiconductor material for photosensitized dyes with enhanced photovoltaic efficiency. − In addition to its semiconductor capabilities, ZnO has been observed to enhance the optical properties within various systems. ZnO was reported to improve the light trapping capabilities of solar cells both as a thin film on an absorbing material and as a nanopatterned surface. , Within our lab, we observed that ZnO nanostructures used in a hierarchical fashion on Au and PEDOT nanocone array surfaces enhanced the antireflective properties of the nanocone arrays via optical coupling . This is striking because while ZnO has no absorptive properties itself, it seemed to enhance those of the host material beneath.…”

“…An SEM image of a ZnO–PEDOT grating sample with a ZnO electrodeposition time of 300 s, as shown in the Supporting Information (Figure S1), revealed sparse coverage of ZnO on the grating surface. The mechanism of the ZnO electrodeposition process has been discussed in previous works ,, and is summarized as follows: At a sufficiently negative applied potential, OH – ions are generated, likely via the reduction of NO 3 – (eq ). The OH – and the Zn 2+ ions then result in the precipitation of ZnO onto the working electrode of either WO 3 or PEDOT gratings (eq ).…”

“…5,6 Within our lab, we observed that ZnO nanostructures used in a hierarchical fashion on Au and PEDOT nanocone array surfaces enhanced the antireflective properties of the nanocone arrays via optical coupling. 7 This is striking because while ZnO has no absorptive properties itself, it seemed to enhance those of the host material beneath. To further our understanding of the optical enhancement of ZnO, we extend our previous work on ZnO nanocone arrays and turn to optical diffraction gratings made of composite electrodeposited ZnO and electrochromic WO 3 or PEDOT to quantify the optical coupling effects.…”

Electrochemiluminescence with semiconductor (nano)materials

“…From an optical point of view, improved light absorption can be induced for nano-and microstructured SC by multiple internal reections or a smooth transition of refractive index, respectively. [117][118][119] Besides, the main advantage of using a structured photoelectrode compared to a planar is that it allows decoupling light absorption and carrier collection. 120 For instance, for SCs suffering from a short minority carrier diffusion length like oxides, using a structure with features smaller than the diffusion length (typically z5 nm for h + in a-Fe 2 O 3 ) can decrease recombination losses.…”