An antireflection transparent conductor with ultralow optical loss (o2 %) and electrical resistance (o6O 2)

Transparent conductors are essential in many optoelectronic devices, such as displays, smart windows, light-emitting diodes and solar cells. Here we demonstrate a transparent conductor with optical loss of B1.6%, that is, even lower than that of single-layer graphene (2.3%), and transmission higher than 98% over the visible wavelength range. This was possible by an optimized antireflection design consisting in applying Al-doped ZnO and TiO2 layers with precise thicknesses to a highly conductive Ag ultrathin film. The proposed multilayer structure also possesses a low electrical resistance (5.75O 2), a figure of merit four times larger than that of indium tin oxide, the most widely used transparent conductor today, and, contrary to it, is mechanically flexible and room temperature deposited. To assess the application potentials, transparent shielding of radiofrequency and microwave interference signals with B30 dB attenuation up to 18 GHz was achieved.Peer ReviewedPostprint (author's final draft

Tunable complete optical absorption in multilayer structures including without lithographic patterns

Controlling the spectral transmission, reflection, and absorption properties of optical structures is of great interest for many applications in photonics. Particularly, perfect absorbers over a wide frequency (wavelength) range are desirable for thin-film thermal emitters, thermo-solar cells, photodetectors, and smart windows. Up to date, several mechanisms have been proposed to achieve nearly 100% absorption in various frequency ranges of the electromagnetic spectrum; starting from microwaves to near infrared (NIR) and visible. One of the first demonstrations of a structure that was absorbing with nearly 100% efficiency was proposed by Landy et al. in 2008,[1] where metamaterial resonator arrays were used to achieve narrowband and highly resonant absorption of GHz and THz waves. The narrowband character of the resonances can be an advantage when absorbers with high quality factor are required and wavelength selectivity is desirable. However, there are many applications that need broadband absorption. To this end great efforts have been made during the last decade, for instance by mixing multiple resonances in a many-fold resonator, which can lead to, e.g., dual band[2] or multiband[3-9] resonant absorption. Unfortunately fabrication of these structures requires sophisticated techniques such as micro- or nano-lithography, severely limiting their scalability and increasing the cost of the absorber.Peer ReviewedPostprint (author's final draft

Tunable complete optical absorption in multilayer structures including without lithographic patterns

Controlling the spectral transmission, reflection, and absorption properties of optical structures is of great interest for many applications in photonics. Particularly, perfect absorbers over a wide frequency (wavelength) range are desirable for thin-film thermal emitters, thermo-solar cells, photodetectors, and smart windows. Up to date, several mechanisms have been proposed to achieve nearly 100% absorption in various frequency ranges of the electromagnetic spectrum; starting from microwaves to near infrared (NIR) and visible. One of the first demonstrations of a structure that was absorbing with nearly 100% efficiency was proposed by Landy et al. in 2008,[1] where metamaterial resonator arrays were used to achieve narrowband and highly resonant absorption of GHz and THz waves. The narrowband character of the resonances can be an advantage when absorbers with high quality factor are required and wavelength selectivity is desirable. However, there are many applications that need broadband absorption. To this end great efforts have been made during the last decade, for instance by mixing multiple resonances in a many-fold resonator, which can lead to, e.g., dual band[2] or multiband[3-9] resonant absorption. Unfortunately fabrication of these structures requires sophisticated techniques such as micro- or nano-lithography, severely limiting their scalability and increasing the cost of the absorber.Peer Reviewe

Light- and Redox-Dependent Force Spectroscopy Reveals that the Interaction between Plastocyanin and Plant Photosystem I Is Favored when One Partner Is Ready for Electron Transfer

Photosynthesis is a fundamental process that converts photons into chemical energy, driven by large protein complexes at the thylakoid membranes of plants, cyanobacteria, and algae. In plants, water-soluble plastocyanin (Pc) is responsible for shuttling electrons between cytochrome b6f complex and the photosystem I (PSI) complex in the photosynthetic electron transport chain (PETC). For an efficient turnover, a transient complex must form between PSI and Pc in the PETC, which implies a balance between specificity and binding strength. Here, we studied the binding frequency and the unbinding force between suitably oriented plant PSI and Pc under redox control using single molecule force spectroscopy (SMFS). The binding frequency (observation of binding-unbinding events) between PSI and Pc depends on their respective redox states. The interaction between PSI and Pc is independent of the redox state of PSI when Pc is reduced, and it is disfavored in the dark (reduced P700) when Pc is oxidized. The frequency of interaction between PSI and Pc is higher when at least one of the partners is in a redox state ready for electron transfer (ET), and the post-ET situation (PSIRed-PcOx) leads to lower binding. In addition, we show that the binding of ET-ready PcRedto PSI can be regulated externally by Mg2+ions in solution

Antireflective Transparent Oleophobic Surface by Non-Interacting Cavities

Oleophobic surfaces have been so far realized using complex micro-scale and nano-scale reentrant geometries where primary and secondary structures or overhang geometries are typically required. Here we propose a new design to create them with non-interacting cavities. The suspension of liquid droplets relies on the mechanism of compression of air under the meniscus leading to stable composite oil-air-solid interfaces. To demonstrate the concept, we make oleophobic surfaces, with contact angle for oleic acid of about 130º (and Hexadecane about 110º), using both micro-holes in silicon and nano-holes in glass. Thanks to the subwavelength dimensions and antireflection effect of the nano-holes, the glass substrate also shows a high degree of optical transparency with optical transmission exceeding that of the initial bare substrate. Crockmeter tests without any significant change of morphology, optical and wetting properties after more than 500 passes also confirm the high mechanical durability of the nano-hole surface. The results indicate the possibility of using the proposed oleophobic surfaces for a wide range of applications, including self-cleaning transparent windows, windshields for automobiles and aircrafts.Peer Reviewe