UV/ozone treated (UVO-treated) TaS2 and non-treated TaS2 nanosheets are introduced into organic photovoltaic cells (OPVs) as hole extraction layers (HEL) and electron extraction layers (EEL). TaS2 nanosheets are obtained via ultrasonic vibration and size-controlled by centrifugation. Atomic force microscopy (AFM) images reveal that the thickness and lateral size of TaS2 nanosheets are approximately 1 and 70 nm, indicating that uniform and ultrathin TaS2 nanosheets are obtained. The work function of TaS2 increases from 4.4 eV to 4.9–5.1 eV after applying UVO treatment by forming Ta2O5. In addition, the power conversion efficiencies of normal OPV with UVO-treated TaS2 and inverted OPV with TaS2 are 3.06 and 2.73%, which are higher than those of OPV without TaS2 (1.56% for normal OPV and 0.22% for inverted OPV). These results indicate that TaS2 is a promising material for HEL and EEL layers in …
WS2 nanosheets obtained through a simple sonication exfoliation method are employed as a hole‐extraction layer to improve the efficiency of organic photovoltaic cells (OPVs). A reduction in the wavenumber difference in the Raman spectra, the appearance of a UV absorption peak, and atomic force microscopy images indicate that WS2 nanosheets are formed through the sonication method. The power conversion efficiency (PCE) values of OPVs with and without untreated WS2 layers are both 1.84%. After performing a UV‐ozone (UVO) treatment on the WS2 surface for 15 min, the PCE increases to 2.4%. Synchrotron radiation photoelectron spectroscopy data show that the work function of WS2 increases from 4.9 eV to 5.1 eV upon UVO treat‐ ment, suggesting that the increase in the PCE value is caused by the band alignment. Upon inserting poly(3,4‐ethylenedioxythiophene):poly(styrene‐sulfonate) (PEDOT …
Graphene oxide (GO) and silane-functionalized GO (sGO) sheets obtained through a simple sonication exfoliation method are employed as hole transport layers to improve the efficiency of organic photovoltaic (OPV) cells and organic light-emitting diodes (OLED). GO was functionalized using (3-glycidyl oxypropyl)trimethoxysilane (GPTMS) and triethoxymethylsilane (MTES). The appearance of new peaks in the Fourier-transform infrared spectra of the sGOs indicates the formation of Si–O–C, Si–O–Si, Si–H, and Si–O–C moieties, which provide evidence of the addition of silane to the GO surface. Furthermore, the appearance of Si–O–Si bonds in the synchrotron radiation photoelectron spectra (SRPES) of the MTES-sGO and GPTMS-sGO samples suggests that silane groups were effectively functionalized onto the GO sheets. An OPV cell with GO layers showed a lower performance with a power conversion …
Mosquitoes are the deadliest animals on earth and are the vectors of several neglected tropical diseases. Recently, essential oils have emerged as potential renewable, cost-effective, and environmentally benign alternatives to synthetic pesticides for control of mosquitoes. In this work, thirteen species of Piper were collected from different areas of central Vietnam. The essential oils were obtained by hydrodistillation and analyzed by gas chromatography–mass spectrometry. The essential oils were screened for mosquito larvicidal activity against Aedes aegypti. Four of the Piper essential oils showed outstanding larvicidal activity against Ae. aegypti, namely P. caninum, P. longum, P. montium, and P. mutabile, with LC 50 and LC 90 values less than 10 µg/mL. Multivariate analysis has correlated concentrations of β-caryophyllene, β-bisabolene, α-pinene, and β-pinene with mosquito larvicidal activity. View Full-Text
It was demonstrated that organolead halide perovskites (OHPs) show a resistive switching behavior with an ultralow electric field of a few kilovolts per centimeter. However, a slow switching time and relatively short endurance remain major obstacles for the realization of the next-generation memory. Here, we report a performance-enhanced OHP resistive switching device. To fabricate topologically and electronically improved OHP thin films, we added hydroiodic acid solution (for an additive) in the precursor solution of the OHP. With drastically improved morphology such as small grain size, low peak-to-valley depth, and precise thickness, the OHP thin films showed an excellent performance as insulating layers in Ag/CH3NH3PbI3/Pt cells, with an endurance of over 103 cycles, a high on/off ratio of 106, and an operation speed of 640 μs and without electroforming. We suggest plausible resistive switching and …
Here, this study successfully fabricates few‐layer MoS2 nanosheets from (NH4)2MoS4 and applies them as the hole transport layer as well as the template for highly polarized organic light‐emitting diodes (OLEDs). The obtained material consists of polycrystalline MoS2 nanosheets with thicknesses of 2 nm. The MoS2 nanosheets are patterned by rubbing/ion‐beam treatment. The Raman spectra shows that {poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole), poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐(benzo[2,1,3]thiadiazol‐4,8‐diyl)]} (F8BT) on patterned MoS2 exhibits distinctive polarization behavior. It is discovered that patterned MoS2 not only improves the device efficiency but also changes the polarization behavior of the devices owing to the alignment of F8BT. This work demonstrates a highly efficient polarized OLED with a polarization ratio of 62.5:1 in the emission spectrum (166.7:1 at the peak intensity of 540 …
A facile, highly efficient approach to obtain molybdenum trioxide (MoO 3)-doped tungsten trioxide (WO 3) is reported. An annealing process was used to transform ammonium tetrathiotungstate [(NH 4) 2 WS 4] to WO 3 in the presence of oxygen. Ammonium tetrathiomolybdate [(NH 4) 2 MoS 4] was used as a dopant to improve the film for use in an electrochromic (EC) cell.(NH 4) 2 MoS 4 at different concentrations (10, 20, 30, and 40 mM) was added to the (NH 4) 2 WS 4 precursor by sonication and the samples were annealed at 500 C in air. Raman, X-ray diffraction, and X-ray photoelectron spectroscopy measurements confirmed that the (NH 4) 2 WS 4 precursor decomposed to WO 3 and the (NH 4) 2 MoS 4–(NH 4) 2 WS 4 precursor was transformed to MoO 3-doped WO 3 after annealing at 500 C. It is shown that the MoO 3-doped WO 3 film is more uniform and porous than pure WO 3, confirming the doping quality …
CH3NH3PbBr3 (MAPbBr3) materials with perovskite structure were grown by a two-step process using Pb(CH3COO)2·3H2O and methyl amine bromide (MABr). By changing the concentration of MABr in isopropyl alcohol (IPA) solvent and the annealing temperature, the shape of CH3NH3PbBr3 materials can be controlled to afford nanocubes, nanowires, nanorods, and wrinkled structures. MAPbBr3 with single cubic structure was obtained at a MABr concentration of 3 mg/mL in IPA, and a nanorod array of MAPbBr3 was realized at a MABr concentration of 9 mg/mL in IPA at room temperature. Uniformly wrinkled shapes were formed after the synthesis temperature was increased to 60 and 90 °C. The X-ray diffraction patterns, Fourier transform infrared spectra, and X-ray photoelectron spectra of CH3NH3PbBr3 nanorods confirmed that the pure perovskite phase was obtained by dipping Pb(CH3COO)2·3H2O in …
CsPbX3 (X = halide, Cl, Br, or I) all‐inorganic halide perovskites (IHPs) are regarded as promising functional materials because of their tunable optoelectronic characteristics and superior stability to organic–inorganic hybrid halide perovskites. Herein, nonvolatile resistive switching (RS) memory devices based on all‐inorganic CsPbI3 perovskite are reported. An air‐stable CsPbI3 perovskite film with a thickness of only 200 nm is successfully synthesized on a platinum‐coated silicon substrate using low temperature all‐solution process. The RS memory devices of Ag/polymethylmethacrylate (PMMA)/CsPbI3/Pt/Ti/SiO2/Si structure exhibit reproducible and reliable bipolar switching characteristics with an ultralow operating voltage (<+0.2 V), high on/off ratio (>106), reversible RS by pulse voltage operation (pulse duration < 1 ms), and multilevel data storage. The mechanical flexibility of the CsPbI3 perovskite RS …
Halide perovskites are emerging materials for future optoelectronics and electronics due to their remarkable advantages such as a high light absorption coefficient, long charge carrier diffusion length, facile synthesis method, and low cost. As polycrystalline halide perovskite thin films, which have been studied so far, have crucial limitations, low-dimensional halide perovskites have attracted attention due to their unique optical properties and charge transport properties, which have not been observed before. This review highlights the limitations of polycrystalline halide perovskites thin films and the unique characteristics of low-dimensional halide perovskite nanostructures including their electrical, optical, and chemical properties. After introducing the recent developments of various low-dimensional halide perovskite nanostructures including the synthesis methods, their properties, and applications, a brief overview of …
Cesium lead iodide (CsPbI3) perovskite, an all‐inorganic halide perovskite, is synthesized on a platinum‐coated silicon substrate for an ultra‐low operating voltage resistive switching memory device by Soo Young Kim, Ho Won Jang, and co‐workers in article number 1705783. An electrochemical metallization mechanism involving metal conducting filaments is proposed to explain the resistive switching behavior which can be applied to next‐generation synaptic devices.
In this report, we present a new approach for the fabrication and application of Cs4PbBr6 microcrystals (Cs4PbBr6 MCs). The Cs4PbBr6 MCs are synthesized via an anti-solvent induced crystallization of PbBr2:CsBr directly in dimethylsulfoxide (DMSO) by introducing HBr (HBr, 48% aqueous solution). The ratio of HBr and DMSO plays a vital role in the formation of Cs4PbBr6. By controlling the HBr/DMSO ratio, pure Cs4PbBr6 or the CsPbBr3 phase can be obtained. The Cs4PbBr6 MCs were initially obtained by adding HBr to CsBr:PbBr2/DMSO. However, on increasing the amount of the added HBr, Cs4PbBr6 MCs were converted to CsPbBr3 MCs and the photoluminescence (PL) disappeared. It was also found that CsPbBr3 MCs can be transformed to Cs4PbBr6 MCs by simply adding DMSO to the dried CsPbBr3 MCs. The Cs4PbBr6 MCs exhibit a strong PL at 516 nm with a full width at half-maximum of 25 nm …
In this research, we investigate the effect of metal doping on the electrochromic (EC) performance of tungsten trioxide (WO3) films. These films were prepared by a novel method involving solution processing and thermal annealing. In this procedure, ammonium tetrathiotungstate ((NH4)2WS4) was dissolved in dimethylformamide at a high concentration ratio (200 mg mL−1) to obtain a homogeneous solution and then spin-coated onto the indium thin oxide (ITO) substrate for use as a working electrode. Subsequently, the film was annealed at the different temperatures (200, 300, 400, and 500 °C) to form a crystal structure of WO3. X-ray diffraction, Raman, and X-ray photoelectron spectroscopic results confirm the crystal formation of WO3. Moreover, in order to improve the electrochromic performance, different concentrations (10, 20, 30, and 40 mM) of different metal chlorides such as PtCl4, PdCl2, AuCl3, AgCl …
Organic–inorganic halide perovskite materials have attracted significant attention during the last few years because of their superior properties for electronic and optoelectronic devices, such as their long charge‐carrier diffusion lengths and high photoluminescence quantum yields of up to 100% with tunable bandgaps over the entire visible spectral range. In addition to solar cells, light‐emitting diodes represent a fascinating application for halide perovskite materials. Here, the recent progress relating to halide perovskite LEDs is reviewed. The current strategies for improving the performance of halide LEDs, focusing on morphological engineering, dimensional engineering, compositional engineering, surface passivation, interfacial engineering, and the plasmonic effect are discussed. The challenges and perspectives for the future development of halide perovskite LEDs are also considered.
We demonstrate a facile and efficient method for the synthesis of a metal-doped WS2nanoflower (NF) catalyst. We also report its application for the electrocatalytic hydrogen evolution reaction (HER). The flower-like WS2 particles were produced by a hydrothermal reaction, and, subsequently, the WS2 was doped with metal chlorides such as AuCl3, AgCl, PtCl2, and PdCl2, followed by reduction with sodium borohydride to form metal-doped WS2 NFs. The Pd-doped WS2 NF catalyst showed a high HER performance, having a Tafel slope of 54 mV/dec and an overpotential of -175 mV at −10 mA cm−2. The improvement is attributed to the energy band alignment near the H+/H2reduction potential and the large surface area of the WS2 NFs.
