Yinong Wang

The nanoporous (NP) GaN distributed Bragg reflector (DBR) was prepared by using electrochemical etching. Then the NP-GaN DBR was pretreated by using ozone treatment. Atomic force microscopy and X-ray diffraction (XRD) were used to investigate the influence of ozone treatment on the structure of the substrates. The hybrid organic–inorganic CH₃NH₃PbI₃ perovskite films were grown on the NP-GaN DBR and reference substrates by using a one-step solution method. The XRD and field emission scanning electron microscopy test results indicate the high quality of the prepared CH₃NH₃PbI₃ perovskite films. The photoluminescence intensity of the prepared CH₃NH₃PbI₃ perovskite film on the NP-GaN DBR substrate is ~ 3.5 times higher than that of the film on the reference substrate, with a 3.6 nm spectral blue-shift. The enhancement should be contributable to amplify spontaneous emission by resonant cavity, while the blue-shift could be contributable to stoichiometric difference of the films on different substrates.

The magnetic properties of π-conjugated bis (8-hydroxyquinoline) manganese (Mnq₂) crystals are investigated. Rod-shaped Mnq₂ crystals are prepared by using the physical vapor deposition method. Field emission scanning electronic microscopy spectra show that the Mnq₂ nanorods have perfect plane quadrangular ends. Energy dispersive spectrometer and X-ray photoelectron spectroscopy analysis demonstrates that the powders and nanorods are the same compound with a high purity. X-ray diffraction analysis shows the high crystal quality of the prepared Mnq₂ nanorods. The magnetic measurement, using alternating gradient magnetometer and magnetic property measurement system superconducting quantum interference device vibrating sample magnetometer, indicates that the prepared Mnq₂ nanorods show a paramagnetic property at room temperature. First-principles density functional theory (DFT) calculations are used to study the electronic structure and magnetic properties of the prepared Mnq₂ crystals. DFT calculations show that the magnetic moment of the Mnq₂ isolated molecule is 5 μ_B, which mainly comes from the localized Mn 3d orbital. The energy difference between the antiferromagnetic and ferromagnetic states of the Mnq₂ monoclinic cell is only 0.1 meV, which may explain the paramagnetic property observed in the prepared Mnq₂ nanorods and also indicates the difficulty of preparing intrinsic ferromagnetic Mnq₂ crystals.

The process of ion implantation often involves vacancy generation and migration. The vacancy generation and migration near a monocrystalline silicon surface during three kinds of energetic Si₃₅ cluster ion implantations were investigated by molecular dynamics simulations in the present work. The patterns of vacancy generation and migration, as well as the implantation-induced amorphous structure, were analyzed according to radial distribution function, Wigner–Seitz cell, and identify diamond structure analytical methods. A lot of vacancies rapidly generate and migrate in primary directions and form an amorphous structure in the first two picoseconds. The cluster with higher incident kinetic energy can induce the generation and migration of more vacancies and a deeper amorphous structure. Moreover, boundaries have a loading–unloading effect, where interstitial atoms load into the boundary, which then acts as a source, emitting interstitial atoms to the target and inducing the generation of vacancies again. These results provide more insight into doping silicon via ion implantation.

Supercapacitors are a highly promising class of energy storage devices due to their high power density and long life cycle. Conducting polymers (CPs) and organic molecules are potential candidates for improving supercapacitor electrodes due to their low cost, large specific pseudocapacitance and facile synthesis methods. Graphene, with its unique two-dimensional structure, shows high electrical conductivity, large specific surface area and outstanding mechanical properties, which makes it an excellent material for lithium ion batteries, fuel cells and supercapacitors. The combination of CPs and graphene as electrode material is expected to boost the properties of supercapacitors. In this review, we summarize recent reports on three different CP/graphene composites as electrode materials for supercapacitors, discussing synthesis and electrochemical performance. Novel flexible and wearable devices based on CP/graphene composites are introduced and discussed, with an eye to recent developments and challenges for future research directions.