Multifunctional ytterbium oxide buffer for perovskite solar cells

Perovskite solar cells (PSCs) comprise a solid perovskite absorber sandwiched between several layers of different charge-selective materials, ensuring unidirectional current flow and high voltage output of the devices. A ‘buffer material’ between the electron-selective layer and the metal electrode in p-type/intrinsic/n-type (p-i-n) PSCs (also known as inverted PSCs) enables electrons to flow from the electron-selective layer to the electrode. Furthermore, it acts as a barrier inhibiting the inter-diffusion of harmful species into or degradation products out of the perovskite absorber. Thus far, evaporable organic molecules and atomic-layer-deposited metal oxides have been successful, but each has specific imperfections. Here we report a chemically stable and multifunctional buffer material, ytterbium oxide (YbOx), for p-i-n PSCs by scalable thermal evaporation deposition. We used this YbOx buffer in the p-i-n PSCs with a narrow-bandgap perovskite absorber, yielding a certified power conversion efficiency of more than 25%. We also demonstrate the broad applicability of YbOx in enabling highly efficient PSCs from various types of perovskite absorber layer, delivering state-of-the-art efficiencies of 20.1% for the wide-bandgap perovskite absorber and 22.1% for the mid-bandgap perovskite absorber, respectively. Moreover, when subjected to ISOS-L-3 accelerated ageing, encapsulated devices with YbOx exhibit markedly enhanced device stability

A Flexible and Boron-Doped Carbon Nanotube Film for High-Performance Li Storage

© Copyright © 2019 Wang, Guo, Lu, Zhang, Hou and Liang. Boron-doped carbon nanotubes are a promising candidate for Li storage due to the unique electronic structure and high crystallinity brought by the boron dopants. However, the relatively low Li storage capacity has limited its application in the electrochemical energy storage field, which is mainly caused by the predominantly intact graphitic structure on their surface with limited access points for Li ion entering. Herein, we report a novel B-doped CNTs (py-B-CNTs) film, in which the CNTs possess intrinsically rough surface but flat internal graphitic structure. When used as a flexible anode material for LIBs, this py-B-CNTs film delivers significantly enhanced capacity than the conventional B-doped CNTs or the pristine CNTs films, with good rate capability and excellent cycling performance as well. Moreover, this flexible film also possesses excellent mechanical flexibility, making it capable of being used in a prototype flexible LIB with stable power output upon various bending states

Enhanced electrochemical stability of carbon-coated antimony nanoparticles with sodium alginate binder for sodium-ion batteries

The poor cycling stability of antimony during a repeated sodium ion insertion and desertion process is the key issue, which leads to an unsatisfactory application as an anode material in a sodium-ion battery. Addressed at this, we report a facile two-step method to coat antimony nanoparticles with an ultrathin carbon layer of few nanometers (denoted Sb@C NPs) for sodium-ion battery anode application. This carbon layer could buffer the volume change of antimony in the charge-discharge process and improve the battery cycle performance. Meanwhile, this carbon coating could also enhance the interfacial stability by firmly connecting the sodium alginate binders through its oxygen-rich surface. Benefitted from these advantages, an improved initial discharge capacity (788.5 mA h g −1 ) and cycling stability capacity (553 mA h g −1 after 50 times cycle) have been obtained in a battery using Sb@C NPs as anode materials at 50 mA g −1

A freestanding CNTs film fabricated by pyrrole-modified CVD for capacitive deionization

Carbon nanotubes (CNTs) are an excellent electrode material for capacitive deionization (CDI), due to their excellent electronic conductivity and outstanding chemical/physical stability. Their powder form and easy aggregation, however, have greatly limited their practical CDI performance. Aiming to address this issue, the authors report a freestanding CNT film which was fabricated by floating-catalyst chemical vapor deposition, as a binder-free electrode for CDI. By simply adjusting the pyrrole content in the precursor, the morphology of the resulting CNT film can be tuned to meet the requirements of CDI. In the presence of 2 wt.% pyrrole, the CNT film with a mesoporous structure exhibited a large specific surface area of 198 m2/g and an increased electric double-layer capacity (40 F/g), which is more than two times as large as that of the pristine CNT film. Due to these merits, the electrosorption capacity for sodium chloride (NaCl) of the CNT film electrode (11·39 mg/g) has been greatly improved compared with that of the pristine CNT film (4·52 mg/g), showing a good potential for large-scale practical CDI

Hierarchically stacked reduced graphene oxide/carbon nanotubes for as high performance anode for sodium-ion batteries

Sodium has attracted an increasing amount of attention as an alternative element to lithium for energy storage due to its low cost and wide distribution, although the intercalation problem for sodium ions in conventional anode materials, due to their larger ionic size, still has to be overcome in order to utilize this element. Herein, we report a carbon-based hybrid material that is composed of stacked reduced graphene oxide/carbon nanotubes (rGO/CNTs) with a hierarchical and open structure to accommodate Na ions, which was fabricated by a liquid-phase oxidative exfoliation and subsequent reduction. This rGO/CNTs hybrid material features a hierarchical nanostructure with rGO nanosheets homogeneously spaced by monodisperse CNTs. The increased interlayer space between individual rGO nanosheets, which resulted from the inserted CNTs, is beneficial for highly efficient and reversible Na ion intercalation, leading to a high and stable capacity of 295 mAhg −1 at 50 mAg −1 for 200 cycles

A hierarchical porous Fe-N impregnated carbon-graphene hybrid for high-performance oxygen reduction reaction

A Fe-N impregnated carbon in a hybrid with in-situ grown graphene from hierarchical porous carbon has been obtained for high-performance oxygen reduction reaction (ORR) catalysis. This hybrid material combines the desirable characteristics for the ORR, including Fe-N active sites, high surface area, good electron conductivity, and hierarchical channels for mass diffusion. As a result, this catalyst exhibits a very positive reaction onset potential ( 0.05 V vs. Ag/AgCl), a high ORR current density, and a complete four-electron ORR pathway, which are even better than a commercial 20% Pt/C catalyst. We further reveal the synergistic ORR enhancement from the controlled Fe-N impregnation in the doped carbon-graphene hybri

High-<i>κ</i> van der Waals Oxide MoO₃ as Efficient Gate Dielectric for MoS₂ Field-Effect Transistors

Two-dimensional van der Waals crystals (2D vdW) are recognized as one of the potential materials to solve the physical limits caused by size scaling. Here, vdW metal oxide MoO3 is applied with the gate dielectric in a 2D field-effect transistor (FET). Due to its high dielectric constant and the good response of MoS2 to visible light, we obtained a field effect transistor for photodetection. In general, the device exhibits a threshold voltage near 0 V, Ion/Ioff ratio of 105, electron mobility about 85 cm2 V−1 s−1 and a good response to visible light, the responsivity is near 5 A/W at low laser power, which shows that MoO3 is a potential material as gate dielectric

Carbon Nanotubes@Nickel Cobalt Sulfide Nanosheets for High‐Performance Supercapacitors

© 2020 Wiley-VCH GmbH As new and alternative energy storage devices to batteries and traditional capacitors, supercapacitors exhibit both high power and high energy density as well as good cycle life. NiCo2S4, a spinel-structured transition metal sulfide with a high specific capacity, is considered to be a promising electrode material for supercapacitors with great application potential. However, the poor electrical conductivity of NiCo2S4 results in poor rate and cycle performance of the material, which limits its practical application. In this work, we design a composite by loading NiCo2S4 on the surface of carbon nanotubes (CNTs) to enhance the conductivity. The best-performing CNTs@NiCo2S4 electrode materials were obtained after the optimized heat-treatment of CNTs@SiO2 precursors. At a current density of 1 A g−1, the CNTs@NiCo2S4 composite exhibits a specific capacity of 216.4 mAh g−1 and a capacity retention of 75 % after 2000 cycles. Even at a high current density of 5 A g−1, the capacity can still retain 87 % of that under 1 A g−1. It is demonstrated that the electrochemical performance of NiCo2S4 can be effectively boosted by combining with conductive CNTs