All-inorganic cesium lead bromide (CsPbBr 3 ) perovskite quantum dots (QDs) have recently emerged as highly promising solution-processed materials for nextgeneration light-emitting applications. They combine the advantages of QD and perovskite materials, which makes them an attractive platform for achieving high optical gain with high stability. Here, we report an ultralow lasing threshold (0.39 μJ/cm 2 ) from a hybrid vertical cavity surface emitting laser (VCSEL) structure consisting of a CsPbBr 3 QD thin film and two highly reflective distributed Bragg reflectors (DBRs). Temperature dependence of the lasing threshold and longterm stability of the device were also characterized. Notably, the CsPbBr 3 QDs provide superior stability and enable stable device operation over 5 h/1.8 × 10 7 optical pulse excitations under ambient conditions. This work demonstrates the significant potential of CsPbBr 3 perovskite QD VCSELs for highly reliable lasers, capable of operating in the short-pulse (femtosecond) and quasi-continuous-wave (nanosecond) regimes.
[1] The ISUAL experiment on the FORMOSAT-2 satellite has confirmed the existence of ionization and Lyman-Birge-Hopfield (LBH) band emissions in elves. In this paper, an in-depth study of the ISUAL recorded elves was carried out. Numerical simulation results of elves based on an electromagnetic finite difference time domain (FDTD) model of the emissions between 185-800 nm and of their spatial-temporal evolution are presented. To account for the effect of atmospheric attenuation, three major attenuation mechanisms: O 2 , O 3 , and molecular Rayleigh scattering are considered. Validations of the electromagnetic FDTD model were conducted in three ways: by comparing the calculated and observed photon fluxes in the ISUAL spectrophotometric channels, by directly comparing the simulated and observed morphologies of elves, and by comparing the computed photon counts of the ISUAL Imager based on the derived peak currents for two elve-associated NLDN (National Lightning Detection Network) cloud-to-ground discharges (CGs) with those recorded by the ISUAL Imager. In all three ways, very good agreement was achieved.
Field-induced ionic motions in all-inorganic CsPbBr3 perovskite quantum dots (QDs) strongly dictate not only their electro-optical characteristics but also the ultimate optoelectronic device performance. Here, we show that the functionality of a single Ag/CsPbBr3/ITO device can be actively switched on a sub-millisecond scale from a resistive random-access memory (RRAM) to a light-emitting electrochemical cell (LEC), or vice versa, by simply modulating its bias polarity. We then realize for the first time a fast, all-perovskite light-emitting memory (LEM) operating at 5 kHz by pairing such two identical devices in series, in which one functions as an RRAM to electrically read the encoded data while the other simultaneously as an LEC for a parallel, non-contact optical reading. We further show that the digital status of the LEM can be perceived in real time from its emission color. Our work opens up a completely new horizon for more advanced all-inorganic perovskite optoelectronic technologies.
[1] On 22 July 2007, 37 blue jets/starters and 1 gigantic jet occurring over a thunderstorm in the Fujian province of China were observed from the Lulin observatory on the central mountain ridge of Taiwan. The majority of the jets were observed to occur in a 5 min window during the mature phase of the jet-producing thunderstorm. These jets have significant red band emissions. However, the blue emissions from these jets were not discernible due to severe atmospheric scattering. A model estimation of the emissions from a streamer reveals that the red emissions in blue starters and blue jets are mainly from the nitrogen first positive band (1PN 2 ). The type II gigantic jet is the first of this type that was observed from the ground. The generation sequence of the gigantic jet begins with a blue starter, then a blue jet occurs at the same cloud top after ∼100 ms and finally develops into a gigantic jet ∼50 ms later. Using "optical strokes" as surrogates of the lightning strokes, the correlations between jets and the cloud lightning are explored. The results indicate that the occurrence of jets can be affected by the preceding local cloud-to-ground (CG) lightning or nearby lightning (intracloud (IC) or CG), while in turn the jets might also affect the ensuing lightning activity.
An InGaN-based dual-wavelength blue/green (470nm∕550nm) light emitting diode (LED) with three terminal operations has been designed and fabricated by using sapphire laser lift-off and wafer-bonding schemes. The device is equivalent to a parallel connection of blue and green LEDs; thus the effective electrical resistance of the device could be reduced. The luminous efficiency is 40lm∕W at 20mA, accompanied by a broad electroluminescence emission with a combination of blue and green colors. This monolithically integrated dichromatic lighting structure has great potential in the application of the solid-state lighting.
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