A novel method of oxide semiconductor nanoparticle synthesis is proposed based on high-voltage, high-current electrical switching discharge (HVHC-ESD). Through a subsecond discharge in the HVHC-ESD method, we successfully synthesized zinc oxide (ZnO) nanorods. Crystallography and optical and electrical analyses approve the high crystal-quality and outstanding optoelectronic characteristics of our synthesized ZnO. The HVHC-ESD method enables the synthesis of ZnO nanorods with ultraviolet (UV) and visible emissions. To demonstrate the effectiveness of our prepared materials, we also fabricated two UV photodetectors based on the ZnO nanorods synthesized using the subsecond HVHC-ESD method. The UV-photodetector test under dark and UV light irradiation also had a promising result with a linear ohmic current−voltage output. In addition to the HVHC-ESD method's excellent tunability for ZnO properties, this method enables the rapid synthesis of ZnO nanorods in open air and water. The results demonstrate the preparation, highlight the synthesis of fine hexagonal-shaped nanorods under a second with controlled oxygen vacancies, and point defects for a wide range of applications in less than a second.
Cuprous oxide (Cu2O) crystals and films of 10–65 nm thickness are investigated via electron diffraction, scanning tunneling microscopy (STM), and photoluminescence (PL) spectroscopy at temperature between 100 to 300 K. While the chemical composition and surface morphology of both systems are identical, large differences are found in the optical response. Bulk Cu2O shows pronounced PL peaks at 620, 730, and 920 nm, compatible with the radiative decay of free and bound excitons, whereas broad and asymmetric peaks at 775 and 850 nm are found for Cu2O films grown on Au(111) and Pt(111) supports. The latter represent the PL signature of VO2+ and VO+ defects, being inserted with substrate‐dependent concentrations due to the oxygen‐poor preparation of the Cu2O films. Despite the strong VO signature in PL, all Cu2O samples show p‐type conductance behavior in STM spectroscopy, indicating an abundance of Cu defects in the lattice. The fact that O vacancies still govern the thin‐film PL is explained by a more efficient recombination via VO‐ than Vcu‐emission channels, as the latter requires exciton formation first. Herein, the high sensitivity of low‐temperature PL to probe the defect landscape of dielectrics, being neither reached by photoelectron spectroscopy nor scanning probe techniques is demonstrated.
In this study, we deposited Cu 2 ZnSnS 4 (CZTS) thin films with various thicknesses using electrodeposition and sputtering methods to exploit them as counter electrodes (CEs) in Zn 2 SnO 4 -based dye-sensitized solar cells (DSSCs). The ternary Zn 2 SnO 4 compound with wide bandgap energy, large corrosive resistivity, high electron mobility, and an appropriate conduction band edge position concerning the dye molecules (N719) can be an outstanding alternative for photoanode besides CZTS CE in DSSCs. On the other hand, CZTS is an impressive candidate as a CE material, but its electrocatalytic activity for the recovery of I − /I − 3 ionic species can be different depending on the synthesis process. Our results indicated the creation of porous morphology in the solution-based deposited films, which yields higher electrocatalytic activity in the CE performance in comparison with the physical deposition method, resulting in short circuit current densities of 9.77 and 8.40 mA cm −2 and open-circuit voltages of 633 and 583 mV for the DSSCs prepared by the respective techniques. The large active area and highly crystallized CZTS films, prepared by the electrodeposition method, led to an around 50% efficiency improvement compared to the widely used, more expensive platinum.
Global photoluminescence (PL) and spatially resolved scanning tunneling microscopy (STM) luminescence are compared for thick Cu 2 O films grown on Au(111). While the PL data reveal two peaks at 750 and 850 nm, assigned to radiative electron decays via localized gap states induced by O vacancies, a wide-band emission between 700 and 950 nm is observed in STM luminescence. The latter is compatible with cavity plasmons stimulated by inelastic electron tunneling and contains no spectral signature of the Cu 2 O defects. The STM luminescence is nonetheless controlled by O vacancies that provide inelastic excitation channels for the cavity plasmons. In fact, the emission yield sharply peaks at 2.2 V sample bias, when tip electrons are resonantly injected into O defect states and recombine with holes at the valence-band top via plasmon stimulation. The spatially confined emission centers detected in photon maps of the Cu 2 O films are therefore assigned to excitation channels mediated by single or few O vacancies in the oxide matrix.
Environmental benign and stable kesterite Cu2ZnSnS4 (CZTS) photovoltaics provides an intriguing alternative to conventional solar cells. However, further development is required for boosting the Voc-deficit in CZTS photovoltaic to enhance the cell function. Intending to obtain high-quality CZTS powder as the basis, here we report a comprehensive study of the vacuum annealing process (including annealing temperature, duration, and heating rates) for synthesized powder with the ball-milling method, which leads to a high-quality kesterite structure. According to analysis outcomes, there are not any significant differences in structures of differently milled specimens while the optical and morphological findings exhibit distinctive results. In short, the 10 h milled powder annealed at 500 °C for 5 h with a 9 °C min−1 heating rate possesses a high-quality structure alongside the desired 1.53 eV bandgap and optimum morphological characteristics.
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