Synergistic effect of indium doping and chlorine surface passivation on CsPbI3 perovskite quantum dots for deep-red light-emitting devices.

Deep-red CsPbI3 perovskite quantum dots (PeQDs) are essential for high-efficiency perovskite light-emitting diodes (PeLEDs) because of their high color purity and high photoluminescence quantum yield (PLQY). The synergetic strategy of indium (In) doping and chlorine (Cl) surface passivation not only partially replaced Pb2+ ions with the smaller ionic In3+ but also filled I- vacancies by Cl- on the surface, maintaining the humidity stability for more than 24 days and yielding excellent PLQY. Benefiting from this synergetic strategy, deep-red (approximately at 683 nm) CsPbI3 PeLEDs showed a maximum luminance and external quantum efficiency (EQE) of 311 cd m-2 and 8.32%, respectively.

Upconversion emissions induced by 1550 nm in near-stoichiometric Er:LiNbO3 crystal.

To increase the photovoltaic efficiency of solar cells, green and red upconversion (UC) emissions produced at an excitation of 1550 nm were investigated. A drastically enhanced red UC emission was observed in near-stoichiometric LiNbO(3) crystal heavily doped with Er(3+) ions (Er:NSLN). Raman spectra showed that the maximum phonon energy shifted from 631 cm(-1) in Er(3+)-doped congruent LiNbO(3) (Er:CLN) to 871 cm(-1) in Er:NSLN crystal. The time decay of the (4)S(3/2)→(4)I(15/2) transition suggested that the Er(3+) cluster sites (Er(Li)(2+)-Er(Nb)(2-)) were dissociated in the Er:NSLN crystal. The visible UC luminescence converted from near infrared at the wavelength of 1550 nm was important to enlarge the solar spectrum response of solar cell.

Upconversion white-light emission in Ho3+/Yb3+/Tm3+ tridoped LiNbO3 single crystal.

Ho3+/Yb3+/Tm3+ tridoped LiNbO3 single crystal exhibiting intense upconversion white light under 980 nm excitation has been successfully fabricated by the Czochralski method. The tridoped LiNbO3 single crystal offers power dependent color tuning properties by simply changing excitation power. Efficient three-photon blue upconversion emission and two-photon green and red upconversion emissions have been observed. In addition, the red emission of Ho3+ originates dominantly from the nonradiative decay of green emission. The LiNbO3 with upconversion white light will be a potential laser candidate material.

Highly efficient 1.54 µm emission in Zr/Yb/Er-codoped LiNbO3 crystal.

Codoping with Zr(4+) ions enhances the 1.54 µm emission in Yb/Er:LiNbO(3) crystal by about three times. Optical damage resistant Zr(4+) ion increases the maximum phonon energy of Er:LiNbO(3) host, which is favorable for the nonradiative relaxation from (4)I(11/2) to (4)I(13/2) state (Er). The time decay spectra show that the incorporation of Zr(4+) ions leads to a shortening lifetime of (4)I(11/2) state (Er), increasing the nonradiative relaxation rate of (4)I(11/2)→(4)I(13/2) (Er) in Yb/Er:LiNbO(3). The 1.54 µm emission enhancement is important to telecommunication application.

Simulation and measurement of optimized microwave reflectivity for carbon nanotube absorber by controlling electromagnetic factors.

Heat-treatments may change the defect and surface organic groups of carbon nanotubes (CNTs), and lead to significant changes in the microwave electromagnetic parameter of CNTs. In this paper, the effect of heat-treatment time and temperature on the complex dielectric constant and permeability as well as the microwave reflectivity of CNTs was investigated. The experimental results indicated that the microwave absorption property of CNTs arises mainly from the high permittivity and consequent dielectric loss. Moreover, the heat-treatment resulted in increased dielectric constant of CNTs and significant improvement of the microwave absorption at frequency values of 2-18 GHz. The microwave reflectivity of CNT composites with a coating thickness of 3 mm was simulated by using the electromagnetic parameters. The absorption peak of CNTs treated at 700 °C had an amplitude of R = -48 dB, which occurred at 9 GHz. Below -10 dB, the composites treated at 900 °C had a bandwidth of 7 GHz. The position of the absorption peak concurred with the measured results. The results indicated that the microwave-absorption properties can be modified by adjusting heat-treatment temperature and time.

Investigation on Synthesis, Stability, and Thermal Conductivity Properties of Water-Based SnO2/Reduced Graphene Oxide Nanofluids.

With the rapid development of industry, heat removal and management is a major concern for any technology. Heat transfer plays a critically important role in many sectors of engineering; nowadays utilizing nanofluids is one of the relatively optimized techniques to enhance heat transfer. In the present work, a facile low-temperature solvothermal method was employed to fabricate the SnO2/reduced graphene oxide (rGO) nanocomposite. X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscope (XPS), Raman spectroscopy, and transmission electron microscopy (TEM) have been performed to characterize the SnO2/rGO nanocomposite. Numerous ultrasmall SnO2 nanoparticles with average diameters of 3-5 nm were anchored on the surface of rGO, which contain partial hydrophilic functional groups. Water-based SnO2/rGO nanofluids were prepared with various weight concentrations by using an ultrasonic probe without adding any surfactants. The zeta potential was measured to investigate the stability of the as-prepared nanofluid which exhibited great dispersion stability after quiescence for 60 days. A thermal properties analyzer was employed to measure thermal conductivity of water-based SnO2/rGO nanofluids, and the results showed that the enhancement of thermal conductivity could reach up to 31% at 60 °C under the mass fraction of 0.1 wt %, compared to deionized water.