Although colloidal lead halide perovskite quantum dots (PQDs) exhibit desirable emitter characteristics with high quantum yields and narrow bandwidths, instability has limited their applications in devices. In this paper, we describe spray-synthesized CsPbI3 PQD quantum emitters displaying strong photon antibunching and high brightness at room temperature and stable performance under continuous excitation with a high-intensity laser for more than 24 h. Our PQDs provided high single-photon emission rates, exceeding 9 × 106 count/s, after excluding multiexciton emissions and strong photon antibunching, as confirmed by low values of the second-order correlation function g (2)(0) (reaching 0.021 and 0.061 for the best and average PQD performance, respectively). With such high brightness and stability, we applied our PQDs as quantum random number generators, which demonstrably passed all of the National Institute of Standards and Technology’s randomness tests. Intriguingly, all of the PQDs exhibited self-healing behavior and restored their PL intensities to greater than half of their initial values after excitation at extremely high intensity. Half of the PQDs even recovered almost all of their initial PL intensity. The robust properties of these spray-synthesized PQDs resulted from high crystallinity and good ligand encapsulation. Our results suggest that spray-synthesized PQDs have great potential for use in future quantum technologies (e.g., quantum communication, quantum cryptography, and quantum computing).
Recently, conductive-bridging memristors based on metal halides, such as halide perovskites, have been demonstrated as promising components for brain-inspired hardware-based neuromorphic computing. However, realizing devices that simultaneously fulfill all of the key merits (low operating voltage, high dynamic range, multilevel nonvolatile storage capability, and good endurance) remains a great challenge. Herein, we describe lead-free cesium halide memristors incorporating a MoO X interfacial layer as a type of conductive-bridging memristor. With this design, we obtained highly uniform and reproducible memristors that exhibited all-around resistive switching characteristics: ultralow operating voltages (<0.18 V), low variations (<30 mV), long retention times (>106 s), high endurance (>105, full on/off cycles), record-high on/off ratios (>1010, smaller devices having areas <5 × 10–4 mm2), fast switching (<200 ns), and multilevel programming abilities (>64 states). With these memristors, we successfully implemented stateful logic functions in a reconfigurable architecture and accomplished a high classification accuracy (ca. 90%) in the simulated hand-written-digits classification task, suggesting their versatility in future in-memory computing applications. In addition, we exploited the room-temperature fabrication of the devices to construct a fully functional three-dimensional stack of memristors, which demonstrates their potential of high-density integration desired for data-intensive neuromorphic computing. High-performance, environmentally friendly cesium halide memristors provide opportunities toward next-generation electronics beyond von Neumann architectures.
The most attractive aspect of perovskite nanocrystals (NCs) for optoelectronic applications is their widely tunable emission wavelength, but it has been quite challenging to tune it without sacrificing the photoluminescence quantum yield (PLQY). In this work, we report a facile ligand-optimized ion-exchange (LOIE) method to convert room-temperature spray-synthesized, perovskite parent NCs that emit a saturated green color to NCs capable of emitting colors across the entire visible spectrum. These NCs exhibited exceptionally stable and high PLQYs, particularly for the pure blue (96%) and red (93%) primary colors that are indispensable for display applications. Surprisingly, the blue- and red-emissive NCs obtained using the LOIE method preserved the cubic shape and cubic phase structure that they inherited from their parent NCs, while exhibiting high crystallinity and high color-purity. Together with the parent green-emissive NCs, the obtained blue- and red-emissive NCs provided a very wide color gamut, corresponding to a Digital Cinema Initiatives-P3 of 140% or an International Telecommunication Union Recommendation BT.2020 of 102%. With the superior optical merits of these LOIE-manipulated NCs, a corresponding color conversion luminescence device provided a high external quantum efficiency (10.5%) and extremely high brightness (970 000 cd/m2). This study provides a valid route toward highly stable, extremely emissive, and panchromatic perovskite NCs with potential use in a variety of future optoelectronic applications.
Highly sensitive X-ray detection is crucial in, for example, medical imaging and secure inspection. Halide perovskite X-ray detectors are promising candidates for detecting highly energetic radiation. In this report, we describe vacuum-deposited Cs-based perovskite X-ray detectors possessing a p–i–n architecture. Because of the built-in potential of the p–i–n structure, these perovskite X-ray detectors were capable of efficient charge collection and displayed an exceptionally high X-ray sensitivity (1.2 C Gyair –1 cm–3) under self-powered, zero-bias conditions. We ascribe the outstanding X-ray sensitivity of the vacuum-deposited CsPbI2Br devices to their prominent charge carrier mobility. Moreover, these devices functioned with a lowest detection limit of 25.69 nGyair s–1 and possessed excellent stability after exposure to over 3000 times the total dose of a chest X-ray image. For comparison, we also prepared traditional spin-coated CH3NH3-based perovskite devices having a similar device architecture. Their volume sensitivity was only one-fifth of that of the vacuum-deposited CsPbI2Br devices. Thus, all-vacuum deposition appears to be a new strategy for developing perovskite X-ray detectors; with a high practical deposition rate, a balance can be reached between the thickness of the absorbing layer and the fabrication time.
vigorously studied over the past decades since the emergence of blue LED. [1] A myriad of efficient phosphors including yellow emissive Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce 3+ ), blue emissive BaMgAl 10 O 17 :Eu 2+ (BAM:Eu 2+ ), green emissive Si 6−z Al z O z N 8−z :Eu 2+ (0 < z ≤ 4.2) (β-Sialon:Eu 2+ ), and red emissive Y 2 O 3 :Eu 3+ have been commercialized and applied in indoor and outdoor illumination, traffic lights, and display backlight to name but a few. Nonetheless, the high junction temperature of LED chips (usually ≥150 °C) leads to nonradiative relaxation and diminish the luminescence efficiency of phosphors. [2] This phenomenon is widely known as thermal quenching (TQ) and is the main issue in further improving the performance and application of PC-LEDs. [2][3][4] The effect is expected to be even more severe in emerging micro-LED applications due to the proximity of phosphors with the LEDs. Furthermore, in traditional phosphors, the emission comes from atomic electron transition of earth scarce rare-earth elements, and the mining process of these elements poses a great threat to the environment and the health of the miners. [5] Therefore, the development of earth abundant emitters with high efficiency and TQ-resistant is urgent.
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