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The thermochromic properties of bilayer films consisting of a nanostructured VO2 under-layer and top-layers of ZnO, SnO2 or WO3 are presented. In each case, the VO2 under-layer was deposited by electric field assisted AACVD on a fluorine doped tin oxide coated glass substrate, with the metal oxide top-layer deposited using sol–gel spin coating. The deposited films were analysed and characterised using scanning electron microscopy, X-ray powder diffraction, variable temperature UV/Vis/NIR spectroscopy, X-ray photoelectron spectroscopy, glow discharge photoelectron emission spectroscopy and contact angle measurements. Compared to bare VO2 films, the bilayer films exhibit superior thermochromic properties, with dramatic increases in the visible light transmittance (Tvis), integrated luminous transmittance (Tlum) and solar modulation (ΔTsol). The thermochromic efficiency was also improved in some cases, with a reduction in the hysteresis loop width to ca. 10 °C, and a decrease in the transition temperature (Tc), which was as low as 44 °C and 43 °C for VO2/ZnO and VO2/SnO2 films, respectively. The best balance of thermochromic, thermal protection and aesthetic properties was achieved for ZnO coated films, with the VO2 under-layer deposited at a field strength of 1500 V m−1 under a negative DC bias (Tc = 47 °C, Tlum = 61.6%, Tvis = 68% and ΔTsol = 6%). [ABSTRACT FROM AUTHOR]

Carbon nanotubes are shown to be beneficial additives to perovskite solar cells, and the inclusion of such nanomaterials will continue to play a crucial role in the push toward developing efficient and stable device architectures. Herein, titanium dioxide/carbon nanotube composite perovskite solar cells are fabricated, and device performance parameters are correlated with spectroscopic signatures of the materials to understand the origin of performance enhancement. By probing the charge carrier dynamics with photoluminescence and femtosecond transient absorption spectroscopy, the results indicate that charge transfer is not improved by the presence of the carbon nanotubes. Instead, carbon nanotubes are shown to passivate the electronic defect states within the titanium dioxide, which can lead to stronger radiative recombination in the titanium dioxide/carbon nanotube films. The defect passivation allows the perovskite solar cells made using an optimized titanium dioxide/carbon nanotube composite to achieve a peak power conversion efficiency of 20.4% (19% stabilized), which is one of the highest values reported for perovskite solar cells not incorporating a mixed cation light absorbing layer. The results discuss new fundamental understandings for the role of carbon nanomaterials in perovskite solar cells and present a significant step forward in advancing the field of high‐performance photovoltaics. [ABSTRACT FROM AUTHOR]

Thermochromic vanadium dioxide (VO 2) window coatings hold the promise of reducing the energy consumption of the built environment by passively regulating solar heat gain in response to changing conditions. Composite materials with embedded VO 2 particles have shown greatly improved optical performances compared with thin films, however they typically exhibit broadened phase transition hysteresis and gradient widths, which negatively impacts the overall performance. Here, we present a scalable one-step solution based synthesis for a thermochromic smart window coating based on a vanadium dioxide sol-gel containing silica (SiO 2 nanoparticles. We compare the performance of our nanoparticle composite with thin film VO 2 along with composites formed by mixing VO 2 and SiO 2 sol-gels and find that both composites achieve an acceptable visible transmittance (∼ 50%) along with a comparable and competitive solar modulation (12.5% and 16.8% respectively), roughly double that of the plain VO 2 film (6.7%). However, our SiO 2 nanoparticle containing composite also benefits from a narrow transition hysteresis and gradient width (9.4 ∘C and 2.9 ∘C respectively). We predict that this method may subsequently be combined with metal ion doping to control both the optical and phase transition characteristics to achieve composite films with high overall energy saving performances. • Improved visible transmittance due to reduced visible reflectivity. • SiO 2 particles act as a matrix for VO2 domain growth. • VO 2 domains grow larger and are more uniform in size. • Narrow hysteresis and transition gradient for improved overall performance. [ABSTRACT FROM AUTHOR]