W.T. Zheng

Polymer-Passivated Inorganic Cesium Lead Mixed-Halide Perovskites for Stable and Efficient Solar Cells with High Open-Circuit Voltage over 1.3 V.

Cesium-based trihalide perovskites have been demonstrated as promising light absorbers for photovoltaic applications due to their superb composition stability. However, the large energy losses (Eloss ) observed in inorganic perovskite solar cells has become a major hindrance impairing the ultimate efficiency. Here, an effective and reproducible method of modifying the interface between a CsPbI2 Br absorber and polythiophene hole-acceptor to minimize the Eloss is reported. It is demonstrated that polythiophene, deposited on the top of CsPbI2 Br, can significantly reduce electron-hole recombination within the perovskite, which is due to the electronic passivation of surface defect states. In addition, the interfacial properties are improved by a simple annealing process, leading to significantly reduced energy disorder in polythiophene and enhanced hole-injection into the hole-acceptor. Consequently, one of the highest power conversion efficiency (PCE) of 12.02% from a reverse scan in inorganic mixed-halide perovskite solar cells is obtained. Modifying the perovskite films with annealing polythiophene enables an open-circuit voltage (VOC ) of up to 1.32 V and Eloss of down to 0.5 eV, which both are the optimal values reported among cesium-lead mixed-halide perovskite solar cells to date. This method provides a new route to further improve the efficiency of perovskite solar cells by minimizing the Eloss .

The effects of electronic field on the atomic structure of the graphene/α-SiO2 interface

The atomic structure of the graphene/α-SiO(2)(0001) interface under electric field F with different intensities is studied using the density functional theory method. Simulation results indicate that the atomic structure of the graphene/α-SiO(2)(0001) interface has only a slight change under the condition of F≤0.02xa0au. However, the distance between substrate and graphene d(0) changes evidently. Moreover, as F reaches 0.03xa0au, the formation of a C-O covalent bond on the interface is present, which would destroy the excellent electronic properties of graphene. Thus, there exists a maximum for F in application of the graphene.

Synthesis and field electron emission properties of hybrid carbon nanotubes and nanoparticles

Hybrid ZnO-carbon nanotubes as well as nanodiamond-carbon nanotubes were synthesized via a straightforward process of plasma enhanced chemical vapor deposition. For the former, ZnO nanoparticles were instantly coated on the tube surface in the final growing process of carbon nanotubes, while for the latter diamond nanoparticles were grown using pretreatment of a silicon substrate with Ni(NO(3))(2)·6H(2)O/Mg(NO(3))(2)·6H(2)O alcohol solution prior to deposition and a high H(2)/CH(4) gas flow ratio in the deposition process. The morphology and microstructure of the obtained hybrid materials were characterized by transmission electron microscopy. Both hybrid ZnO-carbon nanotubes and nanodiamond-carbon nanotubes exhibited excellent field emission properties.

Size effects on the Kauzmann temperature and related thermodynamic parameters of Ag nanoparticles

Based on the Sutton–Chen many-body potential function, several thermodynamic parameters of Ag are simulated by molecular dynamics. The parameters simulated are size dependences of the Kauzmann temperature TK and melting temperature Tm, and size and temperature dependences of melting enthalpy Hm and melting entropy Sm. The simulation results and the results of the thermodynamic theory models of TK and Tm show good agreement, indicating that as the size of the Ag particles decreases, the TK and Tm functions decrease. However, the ratio of TK and Tm of Ag nanoparticles is size-independent.

Anchoring and Upgrading Ultrafine NiPd on Room‐Temperature‐Synthesized Bifunctional NH2‐N‐rGO toward Low‐Cost and Highly Efficient Catalysts for Selective Formic Acid Dehydrogenation

Hydrogen is widely considered to be a sustainable and clean energy alternative to the use of fossil fuels in the future. Its high hydrogen content, nontoxicity, and liquid state at room temperature make formic acid a promising hydrogen carrier. Designing highly efficient and low-cost heterogeneous catalysts is a major challenge for realizing the practical application of formic acid in the fuel-cell-based hydrogen economy. Herein, a simple but effective and rapid strategy is proposed, which demonstrates the synthesis of NiPd bimetallic ultrafine particles (UPs) supported on NH2 -functionalized and N-doped reduced graphene oxide (NH2 -N-rGO) at room temperature. The introduction of the uf8ffNH2 uf8ffN group to rGO is the key reason for the formation of the ultrafine and well-dispersed Ni0.4 Pd0.6 UPs (1.8 nm) with relatively large surface area and more active sites. Surprisingly, the as-prepared low-cost NiPd/NH2 -N-rGO dsiplays excellent hydrophilicity, 100% H2 selectivity, 100% conversion, and remarkable catalytic activity (up to 954.3 mol H2 (mol catalyst)-1 h-1 ) for FA decomposition at room temperature even with no additive, which is much higher than that of the best catalysts so far reported.

Electronic and magnetic properties of nitrogen-doped graphene nanoribbons with grain boundary

Grain boundary (GB) is a one-dimensional interface between two domains of materials with different crystallographic orientations. We investigate the effect of N-doping on the electronic and magnetic properties for hybrid graphene nanoribbon (GNR) with GB, using density functional theory. We find that substituted N atom energetically prefers to distribute at the GB as well as at the ribbon edges. The substituted N atom can induce a variable total magnetic moment depending on the doping sites. After N doping, the translational GB can be spin polarized with ferromagnetic order, and then several spin configurations are generated considering the magnetic couplings between the magnetic moments localized at the ribbon edges and linear translational GB. However, for N-doped GNR with tilt GB, the magnetic moment is extended and denser at the ribbon edges and linear GB. Moreover, small splits of some peaks at the Fermi level are also observed due to partial polarization of GB.

Spontaneous Silver Doping and Surface Passivation of CsPbI3 Perovskite Active Layer Enable Light-Emitting Devices with an External Quantum Efficiency of 11.2%

Lead halide perovskite nanocrystals are currently under intense investigation as components of solution-processed light-emitting devices (LEDs). We demonstrate LEDs based on Ag doped-passivated CsPbI3 perovskite nanocrystals with external quantum efficiency of 11.2% and an improved stability. Ag and trilayer MoO3/Au/MoO3 structure were used as cathode and anode, respectively, which reduce the electron injection barrier and ensure the high transparency and low resistance of the anode. Silver ions diffuse into perovskite film from the Ag electrode, as confirmed by the elemental mapping, the presence of Ag 3d peaks in the X-ray photoelectron spectrum, and the peak shift in the X-ray diffraction patterns of CsPbI3. In addition to doping, silver ions play the beneficial role of passivating surface defect states of CsPbI3 nanocrystals, which results in increased photoluminescence quantum yield, elongated emission lifetime, and improved stability of perovskite films.