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Herein, a large‐area nanofabrication process is proposed for flexible, ultrathin, and ultrasmooth gold films with extraordinary electro‐optical performance, making them competitive as transparent conductive electrodes (TCEs). The approach circumvents the thermodynamic constraints associated with the physical deposition of thin film electrodes, where 3D growth and metal dewetting delay stable percolation until the deposited film thickness exceeds 8–10 nm. It is demonstrated that a postgrowth ion irradiation procedure of compact gold films with Ar+ beam at very low energies, around 100 eV, predominantly induces ballistic smoothing and grain boundary restructuring. This process finally leads to the formation of ultrasmooth and ultrathin gold films that remain compact even at a thickness of 4 nm, with a sheet resistance in the range of 60 Ω sq−1 and an optical transparency around 80%. Remarkably, the films remain percolated even at thicknesses as low as 3 nm, with a transparency exceeding 90% and a sheet resistance of 190 Ω sq−1. These figures are comparable to those of commercial TCEs and enable simple, scalable, all‐metal transparent contacts on both rigid and flexible substrates, with significant potential for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Header Two-dimensional (2D) Transition Metal Dichalcogenide semiconductors (TMDs) are a promising platform in view of developing a novel generation of optoelectronics devices and renewable photon to energy conversion technologies. However new ultra-compact photon harvesting schemes are urgently required to mitigate their poor photon absorption properties. In this work we propose a novel flat-optic solution where a few layers MoS2 film is conformally deposited on a large area (cm2) nanogrooved template. The subwavelength reshaping of the TMDs film induces the excitation of photonic Rayleigh Anomalies (RA). The latter promote a strong in-plane electromagnetic confinement and can be easily tuned over a broadband spectrum by tailoring the illumination conditions. As a demonstration of the potential of this large-area surface functionalization we employed the hybrid 2D nanopatterns as a photocatalyst in a prototype photobleaching reaction of Methylene Blue (MB) molecules. We demonstrate a strong enhancement of the photochemical MB degradation, well above a factor 2, by effectively tuning the RA mode in resonance to the molecular absorption band. Therefore, these findings pave the way to flat-optics photon harvesting schemes for boosting photoconversion efficiency in large-scale hybrid 2D-TMD/polymer layers, with a strong impact in applications ranging from waste-water remediation to new-generation photonics and renewable energy storage

The urgent environmental and energy challenges require novel solutions for efficient light harvesting and conversion in new-generation ultra-thin devices. Plasmonic nanoantennas and flat optics nanogratings can promote light matter interaction at the nanoscale being very attractive for ultra-thin photonics and sensing applications. In this work we developed two light trapping solutions based on large-scale nanomaterials. The first system is a large-scale (cm2) plasmonic metasurface based on self-organized gold nanostripes. The second is based on the periodic re-shaping of ultra-thin semiconducting MoS2 layers forming large-area flat-optics nanogratings. Under this condition Rayleigh Anomalies can be resonantly excited thus promoting in-plane light confinement and photon absorption into the few-layers material. To demonstrate the impact of these nanopatterned systems in photon harvesting we probed their efficiency into a prototypal photochemical reaction: the photo-bleaching of Methylene Blue (MB). We demonstrate the resonant enhancement of the photo-bleaching of these polluting dye molecules promoted either by the localized plasmon resonance in Au nanostripes or by the Rayleigh Anomaly in flat-optics MoS2 nanogratings. We investigate this effect through a quantitative analysis of the solution photodissociation induced by a monochromatic light. These results show the strong potential of flat-optics templates for light-harvesting and energy conversion in ultra-thin photonic devices.

Novel light harvesting platforms and strategies are crucial to develop renewable photon to energy conversion technologies that overcome the current global energy and environmental challenges. Two-dimensional (2D) transition metal dichalcogenide (TMD) semiconductor layers are particularly attractive for photoconversion applications but new ultra-compact photon harvesting schemes are urgently required to mitigate their poor photon absorption properties. Here, we propose a flat-optics scheme based on nanogrooved ultra-thin MoS 2 layers conformally grown onto large area (cm 2 scale) nanopatterned templates. The subwavelength re-shaping of the 2D-TMD layers promotes the excitation of photonic Rayleigh anomaly (RA) modes, uniquely boosting a strong in-plane electromagnetic confinement. By tailoring the illumination conditions, we demonstrate effective tuning of the photonic anomalies over a broadband visible spectrum across the absorption band of relevant polluting dye molecules. Thanks to the strong photonic in-plane confinement, we achieve a resonant enhancement of the photodissociation rate of methylene blue (MB) molecules, well above a factor of 2. These results highlight the potential of flat-optics photon harvesting schemes for boosting photoconversion efficiency in large-scale hybrid 2D-TMD/polymer layers, with a strong impact in various applications ranging from new-generation photonics to waste water remediation and renewable energy storage.

Advances in surface chemistry of CsPbX 3 (where X = Cl, Br or I) nanocrystals (NCs) enabled the replacement of native chain ligands in solution. However, there are few reports on ligand exchange carried out on CsPbX 3 NC thin films. Solid-state ligand exchange can improve the photoluminescence quantum yield (PLQY) of the film and promote a change in solubility of the solid surface, thus enabling multiple depositions of subsequent nanocrystal layers. Fine control of nanocrystal film thickness is of importance for light-emitting diodes (LEDs), solar cells and lasers alike. The thickness of the emissive material film is crucial to assure the copious recombination of charges injected into a LED, resulting in bright electroluminescence. Similarly, solar cell performance is determined by the amount of absorbed light, and hence the light absorber content in the device. In this study, we demonstrate a layer-by-layer (LbL) assembly method that results in high quality films, whose thicknesses can be finely controlled. In the solid state, we replaced oleic acid and oleylamine ligands with didodecyldimethylammonium bromide or ammonium thiocyanate that enhance the PLQY of the film. The exchange is carried out through a spin-coating technique, using solvents with strategic polarity to avoid NC dissolution or damage. Exploiting this technique, the deposition of various layers results in considerable thickening of films as proven by atomic force microscope measurements. The ease of handling of our combined process ( i.e. ligand exchange and layer-by-layer deposition) enables thickness control over CsPbX 3 NC films with applicability to other perovskite nanomaterials paving the way for a large variety of layer permutations.