Explore the vast range of titles available.

Vanadium dioxide (VO 2 ) is a promising material for thermochromic glazing. However, VO 2 thermochromic smart windows suffer from several problems that prevent commercialization: low luminous transmittance ( T lum ) and low solar modulation ability ( ΔT sol ). The solution to these problems can be sought from nature where the evolution of various species has enabled them to survive. Investigations into the morphology of moths eyes has shown that their unique nanostructures provide an excellent antireflection optical layer that helps moths sharply capture the light in each wavelength from a wide angle. Inspired by this mechanism, a VO 2 thermochromic smart window coated with a TiO 2 antireflection layer with a novel nano-cone structure, is presented in this study to achieve high T lum and ΔT sol . Optimization for the key structure parameters is summarized based on the FDTD numerical simulations. The optimized structure exhibits a T lum of 55.4% with ΔT sol of 11.3%, an improvement of about 39% and 72% respectively compared to the VO 2 window without an antireflection layer. Furthermore, wide-angle antireflection and polarization independence are also demonstrated by this nano-cone coating. This work provides an alternative method to enhance the optical performance of VO 2 smart windows.

We demonstrate that the introduction of an elemental beam of Mn during the molecular beam epitaxial growth of Bi2Se3 results in the formation of layers of Bi2MnSe4 that intersperse between layers of pure Bi2Se3. This study revises the assumption held by many who study magnetic topological insulators (TIs) that Mn incorporates randomly at Bi-substitutional sites during epitaxial growth of Mn:Bi2Se3. Here, we report the formation of thin film magnetic TI Bi2MnSe4 with stoichiometric composition that grows in a self-assembled multilayer heterostructure with layers of Bi2Se3, where the number of Bi2Se3 layers separating the single Bi2MnSe4 layers is approximately defined by the relative arrival rate of Mn ions to Bi and Se ions during growth, and we present its compositional, structural, and electronic properties. We support a model for the epitaxial growth of Bi2MnSe4 in a near-periodic self-assembled layered heterostructure with Bi2Se3 with corresponding theoretical calculations of the energetics of this material and those of similar compositions. Computationally derived electronic structure of these heterostructures demonstrates the existence of topologically nontrivial surface states at sufficient thickness.

Three-dimensional band structure of rock-salt (rs) Cd x Zn 1 − x O ( x  = 1.0, 0.83, and 0.60) have been determined by angle-resolved photoemission spectroscopy (ARPES) using synchrotron radiation. Valence-band features shift to higher binding energy with Zn content, while the conduction band position does not depend strongly on Zn content. An increase of the indirect band gap with Zn-doping is larger than that of the direct band gap, reflecting a weaker hybridization between Zn 3 d and O 2 p than that between Cd 4 d and O 2 p . Two-dimensional electronic states due to the quantization along surface normal direction are formed in the surface accumulation layer and show non-parabolic dispersions. Binding energy of the quantized two-dimensional state is well reproduced using an accumulation potential with the observed surface band bending and the characteristic width of about 30 Å.

Perovskite‐based thermochromic smart windows that can change color have attracted much interest. However, the high transition temperature (>45 °C in air) hinders their practical application. Herein, a near‐infrared (NIR) activated thermochromic perovskite window that enables reversible transition cycles at room temperature is proposed. Under natural sunlight (>700 W m−2), it efficiently harvests 78% NIR light to trigger the thermochromism of perovskites, blocking the heat gain from both the visible and NIR light. Meanwhile, it also exhibits a low mid‐infrared emissivity of <0.3, suppressing thermal radiation to the indoor environment. A field test demonstrates that this smart window can reduce the indoor temperature by 8 °C compared to a normal glass window at noon. The near‐room‐temperature color change, multispectral thermal management, outstanding energy‐saving ability, and climate adaptability, and solution‐based process of this window make it unique and promising for real applications. A self‐activated thermochromic perovskite smart window (T‐PCL window) is developed. This window can smartly harvest the near‐IR part of sunlight to trigger the thermochromism at room temperature. Simultaneously, the T‐PCL window demonstrates room‐temperature solar regulation ability for visible light, shielding effect for near‐IR, and low thermal radiation for mid‐infrared, showing a promising future for application on energy‐efficient buildings.

Thermochromic perovskite smart windows (TPWs) are a cutting-edge energy-efficient window technology. However, like most perovskite-based devices, humidity-related degradation limits their widespread application. Herein, inspired by the structure of medical masks, a unique triple-layer thermochromic perovskite window (MTPW) that enable sufficient water vapor transmission to trigger the thermochromism but effectively repel detrimental water and moisture to extend its lifespan is developed. The MTPW demonstrates superhydrophobicity and maintains a solar modulation ability above 20% during a 45-day aging test, with a decay rate 37 times lower than that of a pristine TPW. It can also immobilize lead ions and significantly reduce lead leakage by 66 times. Furthermore, a significant haze reduction from 90% to 30% is achieved, overcoming the blurriness problem of TPWs. Benefiting from the improved optical performance, extended lifespan, suppressed lead leakage, and facile fabrication, the MTPW pushes forward the wide applications of smart windows in green buildings. Thermochromic perovskite smart windows require humidity for operation, but too much can lead to degradation. Tso and coworkers demonstrate a mask-inspired system for humidity regulation, to extend lifespan and minimize optical haze.

As a promising high mobility p-type wide bandgap semiconductor, copper iodide has received increasing attention in recent years. However, the defect physics/evolution are still controversial, and particularly the ultrafast carrier and exciton dynamics in copper iodide has rarely been investigated. Here, we study these fundamental properties for copper iodide thin films by a synergistic approach employing a combination of analytical techniques. Steady-state photoluminescence spectra reveal that the emission at ~420 nm arises from the recombination of electrons with neutral copper vacancies. The photogenerated carrier density dependent ultrafast physical processes are elucidated with using the femtosecond transient absorption spectroscopy. Both the effects of hot-phonon bottleneck and the Auger heating significantly slow down the cooling rate of hot-carriers in the case of high excitation density. The effect of defects on the carrier recombination and the two-photon induced ultrafast carrier dynamics are also investigated. These findings are crucial to the optoelectronic applications of copper iodide. Deep understanding of defect physics, excitonic properties and the ultrafast carrier dynamics in the high mobility p-type transparent CuI is vital for its optoelectronic applications. Here, Liu et al. employ a synergistic approach to unveil these fundamental properties.

Artificial photosynthesis relies on the availability of semiconductors that are chemically stable and can efficiently capture solar energy. Although metal oxide semiconductors have been investigated for their promise to resist oxidative attack, materials in this class can suffer from chemical and photochemical instability. Here we present a methodology for evaluating corrosion mechanisms and apply it to bismuth vanadate, a state-of-the-art photoanode. Analysis of changing morphology and composition under solar water splitting conditions reveals chemical instabilities that are not predicted from thermodynamic considerations of stable solid oxide phases, as represented by the Pourbaix diagram for the system. Computational modelling indicates that photoexcited charge carriers accumulated at the surface destabilize the lattice, and that self-passivation by formation of a chemically stable surface phase is kinetically hindered. Although chemical stability of metal oxides cannot be assumed, insight into corrosion mechanisms aids development of protection strategies and discovery of semiconductors with improved stability. Metal oxide semiconductors are promising materials for solar energy capture but can suffer from stability problems. Here, the authors present a methodology for evaluating corrosion mechanisms and apply it to BiVO 4 , revealing chemical instabilities that are not predicted from thermodynamic considerations alone.

Cadmium oxide (CdO) is a much-studied wide gap semiconductor with an inherent high mobility of > 100 cm 2 /Vs, high electron concentration of > 10 21  cm −3 and a wide optical transparency window of > 1800 nm. These unique properties make CdO a potential transparent conductor for full spectrum photovoltaics. However, in order to achieve optimum material properties for optoelectronic applications, CdO was grown by vacuum-based physical or chemical vapor deposition methods. In this work, we explored the application of a low-cost sol-gel spin coating method to achieve highly conducting and transparent CdO thin films doped with 0–10% In (CdO:In). We find that while as-grown CdO:In films are nanocrystalline/amorphous with a high resistivity of ~ 1 Ω-cm, polycrystalline and highly conducting films can be obtained after optimized annealing at ≥ 400 °C. However, the electron concentration n saturates at ~ 5 × 10 20  cm −3 for In concentration > 5% (or N In  ~ 1.9 × 10 21  cm −3 ). This low activation of In may be attributed to the high density of native defects and/or impurities incorporated in the sol-gel process. With 5% In doping, we obtained a low resistivity of ρ ~ 2.5 × 10 –4 Ω-cm and a high mobility μ ~ 50 cm 2 /Vs. These values of σ and µ are better than those reported for other TCOs synthesized by solution processes and comparable to conventional commercial TCOs grown by physical vapor deposition methods. Benefiting from their high mobility, these sol-gel CdO:In films are optically transparent over a wide spectral range up to λ > 1800 nm, making them promising as transparent conductors for optoelectronic devices utilizing the infrared photons.

Bandgap integration in a single semiconductor nanostructure is an important task for their applications in photonics and photoelectronics. Herein a two‐step growth of CdS x Se1−x alloy nanoribbon heterostructures along the lateral direction by an improved two‐step magnetic‐pulling chemical vapor deposition (CVD) method is reported. Microstructural characterizations further demonstrate that these ribbons are formed by two separate components along the lateral direction of the nanoribbons, including CdS0.76Se0.24 at the central region and CdS0.44Se0.56 at both lateral sides, respectively. Under a laser excitation, photoluminescence spectrum and 2D emission mapping at the junctions show two different emission bands at 555 and 603 nm, which show agreement with the structural characterization results. More importantly, under 355 nm laser illumination, room‐temperature dual‐wavelength lasing with peak center at 542.3 and 605.2 nm is realized using these sandwich‐like nanoribbons. Additionally, photodetectors based on these achieved nanoribbons are fulfilled with great performance of high responsivity (2.4 × 104 A W−1), high external quantum efficiency of 2.9 × 105%, fast response speed (rise ≈25 ms, decay ≈21 ms), and high I on/I off ratio (106). These structures may offer an interesting system for exploring new applications in multifunctional nanophotonic and optoelectronic devices, such as high‐performance detectors, miniature tunable lasers, and high‐density color displays. Herein, a high‐quality lateral nanoribbon heterostructure with an abrupt interface using a two‐step magnetic‐pulling chemical vapor deposition approach is reported. Room‐temperature dual‐wavelength lasing and high‐performance photodetectors are demonstrated based on these unique nanostructures.

Multiband solar cells offer a promising route to surpass the Shockley-Queisser limit by harnessing sub-bandgap photons through three active energy band transitions. However, realizing their full potential requires overcoming key challenges in material design and device architecture. Here, we propose a novel multiband stacked anti-parallel junction solar cell structure based on highly mismatched alloys (HMAs), in particular dilute GaAsN with ~1–4% N. An anti-parallel junction consists of two semiconductor junctions connected with opposite polarity, enabling bidirectional current control. The structures of the proposed devices are based on dilute GaAsN with anti-parallel junctions, which allow the elimination of tunneling junctions—a critical yet complex component in conventional multijunction solar cells. Semiconductors with three active energy bands have demonstrated the unique properties of carrier transport through the stacked anti-parallel junctions via tunnel currents. By leveraging highly mismatched alloys with tailored electronic properties, our design enables bidirectional carrier generation through forward- and reverse-biased diodes in series, significantly enhancing photocurrent extraction. Through detailed SCAPS-1D simulations, we demonstrate that strategically placed blocking layers prevent carrier recombination at contacts while preserving the three regions of photon absorption in a single multiband semiconductor p/n junction. Remarkably, our optimized five-stacked anti-parallel junctions structure achieves a maximum theoretical conversion efficiency of 70% under 100 suns illumination, rivaling the performance of state-of-the-art six-junctions III-V solar cells—but without the fabrication complexity of multijunction solar cells associated with tunnel junctions. This work establishes that highly mismatched alloys are a viable platform for high efficiency solar cells with simplified structures.