Antireflection (AR) coatings that exhibit multifunctional characteristics, including high transparency, robust resistance to moisture, high hardness, and antifogging properties, were developed based on hollow silica-silica nanocomposites. These novel nanocomposite coatings with a closed-pore structure, consisting of hollow silica nanospheres (HSNs) infiltrated with an acid-catalyzed silica sol (ACSS), were fabricated using a low-cost sol-gel dip-coating method. The refractive index of the nanocomposite coatings was tailored by controlling the amount of ACSS infiltrated into the HSNs during synthesis. Photovoltaic transmittance (TPV) values of 96.86-97.34% were obtained over a broad range of wavelengths, from 300 to 1200 nm; these values were close to the theoretical limit for a lossy single-layered AR coating (97.72%). The nanocomposite coatings displayed a stable TPV, with degradation values of less than 4% and 0.1% after highly accelerated temperature and humidity stress tests, and abrasion tests, respectively. In addition, the nanocomposite coatings had a hardness of approximately 1.6 GPa, while the porous silica coatings with an open-pore structure showed more severe degradation and had a lower hardness. The void fraction and surface roughness of the nanocomposite coatings could be controlled, which gave rise to near-superhydrophilic and antifogging characteristics. The promising results obtained in this study suggest that the nanocomposite coatings have the potential to be of benefit for the design, fabrication, and development of multifunctional AR coatings with both omnidirectional broadband transmission and long-term durability that are required for demanding outdoor applications in energy harvesting and optical instrumentation in extreme climates or humid conditions.

We propose a simple theoretical formula for describing the refractive indices in binary liquid mixtures containing salt ions. Our theory is based on the Clausius-Mossotti equation; it gives the refractive index of the mixture in terms of the refractive indices of the pure liquids and the polarizability of the ionic species, by properly accounting for the volume change upon mixing. The theoretical predictions are tested by extensive experimental measurements of the refractive indices for water-acetonitrile-salt systems for several liquid compositions, different salt species, and a range of salt concentrations. Excellent agreement is obtained in all cases, especially at low salt concentrations, with no fitting parameters. A simplified expression of the refractive index for low salt concentration is also given, which can be the theoretical basis for determination of salt concentration using refractive index measurements.

Photovoltaic (PV) modules are not only an opto‐electrical system, but also opto‐thermal one, where the optical, electrical, and thermodynamic domains are strongly coupled. The means to suppress both light and heat losses in PV modules remains undeveloped. Herein, a universal route to realize both radiative cooling and light management via the ultra‐broadband versatile textures is proposed, originating from the interaction with the visible, near‐infrared, and mid‐infrared electromagnetic waves (EMWs) via geometric, diffractive, and subwavelength optical effects. The sol–gel imprinted ultra‐broadband textures exhibited a near‐unity infrared emissivity over 0.96 at the atmospheric window between 8 to 13 μm for radiative cooling, and a solar transmittance and haze above 0.94 and 0.95 at the wavelengths from 350 to 750 nm, respectively, for light management. Applying the ultra‐broadband textures imprinted glass to silicon PV modules as an encapsulant cover, the short‐circuit current and conversion efficiency were increased by 5.12 and 3.13% in relative terms, respectively. The fabrication of such ultra‐broadband versatile textures was photolithography‐free, scalable, and PV industry compatible, which provided a cost‐effective, long‐term durable, and energy‐efficient means to both light and thermal management through ultra‐broadband matter‐EMW interaction not only in PV modules, but also various opto‐electro‐thermal devices.

We present a novel method for obtaining salt polarizabilities in aqueous solutions based on our recent theory for the refractive index of salt solutions, which predicts a linear relationship between the refractive index and the salt concentration at low concentrations, with a slope determined by the intrinsic values of the salt polarizability and the density of the solution. Here we apply this theory to determine the polarizabilities of 32 strong electrolyte salts in aqueous solutions from refractive index and density measurements. Setting Li + as the standard ion, we then determine the polarizabilities of seven cations (Na + , K + , Rb + , Cs + , Ca 2+ , Ba 2+ and Sr 2+ ) and seven anions (F − , Cl − , Br − , I − , ClO − 4 , NO − 3 and SO − 4 ), which can be used as important reference data.We investigate the effect of temperature on salt polarizabilities, which decreases slightly with increasing temperature. The ion polarizability is found to be proportional to the cube of bare ionic radius (r 3 bare ) for univalent ions, but the relationship does not hold for multivalent ions. Contrary to findings of Krishnamurti, we find no significant linear relationship between ion polarizability and the square of the atomic number (N 2 ) for smaller ions.

As a potential risk to human and environmental health, radio frequency (RF) radiation should be studied due to the higher frequencies and larger bandwidths that may be employed. Electromagnetic interference (EMI) shielding materials can prevent exposure to RF radiation, but most of them are visibly opaque. In this work, we propose and fabricate visibly transparent EMI shielding materials using an ultrathin silver layer sandwiched by oxides (SLSO) as building blocks. The samples with a double-sided SLSO (D-SLSO) structure exhibit the highest EMI shielding effectiveness (SE) of 70 dB at 27.6 GHz (>62 dB on average at 4–40 GHz) and a transmittance close to 90% at a visible wavelength of 550 nm, which is comparable with those of polyethylene terephthalate (PET) and glass substrates. The D-SLSO structure plays a dual role: it suppresses optical reflections as antireflection coatings and enhances EMI shielding via Fabry–Pérot interference. In addition, we discuss the origin of the extraordinary frequency dependence of SE, which monotonically increases, contrary to that of conventional metallic mesh. This report describes SLSO-based transparent EMI shielding materials with record-high SE and visible transmittance that provide optoelectronic applications with robust safety and reliability under RF radiation with high and broad frequencies.

Cuprous oxide films were successfully electrodeposited onto three different substrates through the reduction of copper lactate in alkaline solution at pH = 10. The substrates include indium tin oxide film coated glass, n-Si wafer with (001) orientation and Au film evaporated onto Si substrate. The substrate effects on the structural and optical properties of the electrodeposited films are investigated by in situ voltammetry, current versus time transient measurement, ex situ x-ray diffraction, scanning electron microscopy, UV-vis transmittance and reflectance and photoluminescence techniques. The results indicate that the choice of substrate can strongly affect the film morphology, structure and optical properties.

Foldable paper‐based solar cells are attractive power sources for wearable and portable applications. Currently, low power conversion efficiency (PCE) and degradation under different folding conditions restrict practical applications of paper‐based solar cells. Herein are constructed solar cells on cellophane paper using oxide/ultrathin Ag/oxide (OMO) and perovskite as electrodes and absorbers, respectively. The perovskite solar cell (PSC) on cellophane exhibits a PCE of 13.19%, the highest among all the paper‐based solar cells. More importantly, beneficial from ultrathin cellophane substrates combined with foldable OMO electrodes, PSCs on paper exhibit 50 single folding and 10 dual folding stability: they preserve 85.3 and 84.1% of the initial PCE after −180° and +180° single folding for 50 cycles, respectively; and they remain 67.2 and 55.3% of the initial PCE after 10 inner and outer dual folding cycles, respectively. Furthermore, the solar cells after dual folding show serious cracks and delamination, leading to faster degradation than single folding. The highly efficient, foldable, and lightweight PSCs on cellophane are promising for future self‐powered paper‐based electronic applications.

Exploiting stretchable solar cells that can accommodate large strain and feature high cyclic mechanical endurance is challenging for wearable and skin-interfaced electronics application. In this work, we demonstrated such solar cells using the kirigami design. Experiments and mechanical simulations showed that the kirigami structure effectively imparted stretchability to perovskite solar cells (PSCs) through out-of-plane deformation, which significantly reduced the stress in devices. The kirigami-based PSCs with optimal geometric parameters exhibited high mechanical deformability, including stretchability (strain up to 200%), twistability (angle up to 450°), and bendability (radius down to 0.5 mm). More importantly, the kirigami PSCs revealed high mechanical endurance with almost unchanged performance even after 1000 repetitive stretching, twisting, and bending cycles. This kirigami design for stretchable PSCs presented here provides a promising strategy to achieve high deformability for solar cells as well as other optoelectronic devices.