Aibin Huang

Surface plasmon resonance induced excellent solar control for VO2@SiO2 nanorods-based thermochromic foils

Transition-metal oxide nanocrystals are novel candidates for being used as the hosts of localized surface plasmon resonance because they exhibit fascinating properties arising from the unique characteristics of their outer-d valence electrons. VO₂(M) nanocrystal is well-known due to its reversible metal-insulator transition (MIT) temperature near room temperature (∼68 °C) corresponding to the appearance/disappearance of localized surface plasmon resonance across the MIT. In this study, a microemulsion-based method was introduced to synthesize VO₂(M)@SiO₂ nanoparticles which were applied to prepare VO₂-based thermochromic foils owing to a strong and tunable surface plasmon resonance in the metallic state. The optical transmittance spectra demonstrates that the employment of surface plasmon resonance in VO₂-based thermochromic foils greatly improves their solar regulating efficiency up to 18.54%, and provides an unprecedented insight in optimizing VO₂-based thermochromic windows for solar control.

Synthesis of VO2 nanoparticles by a hydrothermal-assisted homogeneous precipitation approach for thermochromic applications

Thermochromic VO2 particles, which have potential applications in “smart windows” for energy saving, have been successfully prepared by a convenient route combining homogeneous precipitation and hydrothermal processes. As a result, the particle size can be easily tuned from several tens to hundreds of nanometers by controlling the initial vanadium source concentration. Lower concentration yielded large rod-like crystals, while high concentration resulted in small near-spherical nanocrystals. The decrease of the size of VO2 particles leads to an improvement in thermochromic properties, along with a wider hysteresis of the phase transition temperature. In addition, the W-doping can effectively tune the phase transition temperature (Tc) down to ambient temperature with the efficiency of about −21.3 °C per at% W in the doping range from 0 to 2.0 at% W.

Achieving high-performance planar perovskite solar cells with co-sputtered Co-doping NiOx hole transport layers by efficient extraction and enhanced mobility

Perovskite solar cells are some of the most promising photovoltaic devices and they have experienced extraordinary progress in efficiency and fabricating technologies. Herein, we explore the effect of Co-doped NiOx hole transport layers on the electronic structure and photovoltaic properties of PSCs, which were deposited onto FTO substrates via DC magnetron sputtering at room temperature. Appropriate Co-doping can slightly regulate the optical band gap and the Fermi level position, leading to an increased potential cell performance. By virtue of continuously adjusting the power loaded onto the Co target, we can obtain the optimal atomic ratio of the Co:NiOx hole transport layer, and the PSC based on Co:NiOx exhibited a 25% higher efficiency than its undoped counterparts (from 9.46% to 12.61%). Therefore, these results demonstrate that Co is an appropriate dopant and the PSCs based on Co:NiOx layers have a good performance.

Preparation of VxW1−xO2(M)@SiO2 ultrathin nanostructures with high optical performance and optimization for smart windows by etching

A fast, low-temperature hydrothermal method was introduced to prepare a VxW1−xO2(B) ultrathin nanostructure which can be easily transformed into VxW1−xO2(M) via a fast annealing process in an inert atmosphere. Thermochromic foils coated with ultrathin V0.98W0.02O2(M) nanopowders exhibited unsatisfactory optical properties with a weak solar regulation efficiency (ΔTsol, 4.6%) and a low luminous transmittance (Tlum-L, 15.73%) in a low-temperature state. Coating the VxW1−xO2(M) nanostructure with a thin shell of SiO2 can improve the optical performance of the thermochromic foils resulting in ΔTsol of 7.15% and Tlum-L of 25.74%. Furthermore, etching the V0.98W0.02O2(M)@SiO2 core–shell nanostructure with diluted hydrochloric acid (HCl) can optimize the optical properties of the thermochromic foils well, resulting in ΔTsol and Tlum-L of up to 10.18% and 37.37% owing to the decreased size. In summary, we employed a simple method to synthesize V1−xWxO2@SiO2 ultrathin nanostructures and provided new insight into optimizing VO2-based thermochromic windows.

Template-free formation of various V2O5 hierarchical structures as cathode materials for lithium-ion batteries

Various V2O5 hierarchical structures were successfully synthesized via a template-free method by annealing diverse morphological VO2 sub-microspheres which can be facilely tailored by adjusting the solvothermal reaction duration. The VO2 sub-microspheres undergo a solid → yolk–shell → hollow → yolk–shell structure process with increasing time, which is believed to result from an unusual Ostwald-ripening process. After the annealing process, multi-structural VO2 sub-microspheres changed into hierarchical structures including fist-type structures consisting of nanorods, yolk–shell and hollow sub-microspheres composed of nanorods and a yolk–shell construction made up of nanoplates. As the cathode materials for lithium-ion batteries, among them, yolk–shell sub-microspheres comprised of nanoplates exhibited high reversible capacity, excellent cycling stability at high currents and good rate capacities. Without doping and compositing, the electrode delivered reversible capacities of 119.2 and 87.3 mA h g−1 at high current densities of 2400 and 3600 mA g−1, respectively, as well as a capacity retention of 78.31% after 80 cycles at 1200 mA g−1. The excellent electrochemical performance could be attributed to the purity of the phase and synergistic effect between the yolk–shell structure and hierarchical structure of the sub-microspheres, which make the yolk–shell V2O5 hierarchical structure a promising candidate for the cathode material for lithium-ion batteries.

Solar-thermochromism of a hybrid film of VO2 nanoparticles and CoII–Br–TMP complexes

A hybrid film consisting of VO2 nanoparticles and CoII–Br–TMP complexes was prepared. The CoII–Br–TMP complexes containing cobalt(II), trimethylolpropane (CH3CH2C(CH2OH)3, TMP) and bromine were selected to be combined with VO2 nanoparticles for the first time. Evident colour-change behaviour in response to temperature change and enhanced optical performance of this composite were reported.

Hybrid films of VO2 nanoparticles and a nickel(II)-based ligand exchange thermochromic system: excellent optical performance with a temperature responsive colour change

It is well known that excellent optical performance is a vital factor of vanadium dioxide (VO2) thermochromic films. Except for optimizing the properties of VO2 itself as most researchers have been focusing on, hybridizing has been verified to be an effective way to substantially improve the solar regulation efficiency (ΔTsol) and luminous transmittance (Tlum) of the thermochromic films. Therefore, a nickel(II)-based ligand exchange thermochromic system (NLETS), which contains nickel(II), 2,2-dimethylpropane-1,3-diol ((CH3)2C(CH2OH)2) and bromide, is selected in this paper to be combined with VO2 nanoparticles forming a hybrid film. Compared with a pure VO2 film, this novel scheme demonstrates a 127% increase (from 8.02% to 18.19%) in ΔTsol at a rather high Tlum (Tlum,l = 73.36% and Tlum,h = 68.71%). What is more, since the intrinsic colour change of the NLETS from colourless to blue, the hybrid film presents an evident temperature responsive colour change: from yellow to green, which is crucial for exhibition, publicity and promotion of thermochromic products.

Achieving High Current Density of Perovskite Solar Cells by Modulating the Dominated Facets of Room-Temperature DC Magnetron Sputtered TiO2 Electron Extraction Layer

The short circuit current density of perovskite solar cell (PSC) was boosted by modulating the dominated plane facets of TiO2 electron transport layer (ETL). Under optimized condition, TiO2 with dominant {001} facets showed (i) low incident light loss, (ii) highly smooth surface and excellent wettability for precursor solution, (iii) efficient electron extraction, and (iv) high conductivity in perovskite photovoltaic application. A current density of 24.19 mA cm-2 was achieved as a value near the maximum limit. The power conversion efficiency was improved to 17.25%, which was the record value of PSCs with DC magnetron sputtered carrier transport layer. What is more, the room-temperature process had a great significance for the cost reduction and flexible application of PSCs.

Mesostructured perovskite solar cells based on highly ordered TiO2 network scaffold via anodization of Ti thin film

An anodized TiO2 interconnected network was fabricated and utilized as a mesoporous scaffold and electron transporter in perovskite solar cells. By modifying the synthesis parameters, the morphological features of the interconnected TiO2 nanostructures can be widely tuned and precisely controlled. The functional properties of the anodized TiO2 network are found to be severely influenced by morphology as well as the extent of oxidation. The device with the optimized TiO2 network exhibits superior electron extraction and transferability, resulting in conspicuous enhancement of the photocurrent and power conversion efficiency (PCE). This work proposes a promising and facile method for improving the performance of perovskite solar cells.

Fast Fabrication of a Stable Perovskite Solar Cell with an Ultrathin Effective Novel Inorganic Hole Transport Layer

With the aim of fabricating simple, reproducible, and scalable perovskite solar cells (PSCs) with least time consumption, a novel CoOx hole transport layer (HTL) was first proposed and introduced in this work. The CoOx HTL thickness was minimized to about 10 nm with complete coverage on the FTO substrate (F-doped SnO2) by direct current magnetron sputtering. The ultrathin HTL could minimize the incident light loss caused by cobalt ion absorption and reduce the carrier transport loss by shortening the transport path. Copper was incorporated into the CoOx lattice to address the low conductivity of the CoOx film and the energy-level mismatch between CoOx and the perovskite material. On the basis of cobalt-copper binary oxide (Co1-yCuyOx), the highest power conversion efficiency (PCE) of about 10% was achieved, which was acceptable for mass production. Moreover, the deposition of such Co1-yCuyOx films takes only 2 min without size limitation of substrates. A well-functioned device based on the Co1-yCuyOx HTL could hence be fabricated within 100 min. Excellent stability was demonstrated as well, with over 90% of the initial PCE remaining after being stored in a dark and humid environment (relative humidity 60%) for 12 days.