Recently, several types of lead halide perovskites have been demonstrated as active layers in resistive switching memory or artificial synaptic devices for neuromorphic computing applications. However, the thermal instability and toxicity of lead halide perovskites severely restricted their further practical applications. Herein, the environmentally friendly and uniform Cs3Cu2I5 perovskite films are introduced to act as the active layer in the Ag/Cs3Cu2I5/ITO memristor. Generally, the Ag ions could react with iodide ions and form AgI x compounds easily, so the Ag/PMMA/Cs3Cu2I5/ITO memristor was designed by employing the ultrathin polymethylmethacrylate (PMMA) layer to avoid the direct contact between the top Ag electrode and Cs3Cu2I5 perovskite films. After optimization, the obtained memristor demonstrated bipolar resistive switching with low operating voltage (< ±1 V), large on/off ratio (102), stable endurance (100 cycles), and long retention (>104 s). Additionally, biological synaptic behaviors including long-term potentiation and long-term depression have been investigated. By using the MNIST handwritten recognition data set, the handwritten recognition rate based on experimental data could reach 94%. In conclusion, our work provides the opportunity of exploring the novel application for the development of next-generation neuromorphic computing based on lead-free halide perovskites.

In recent years, it has been reported that using ligands modification to passivate the surface is one reasonable approach to improve the optical properties and stability of perovskite quantum dots (QDs). However, a simple and effective way to diminish the aggregation phenomenon of perovskite QDs is still challenging. Herein, a ligand‐engineering strategy is adopted to fabricate CsPbBr3 QDs by applying a shorter capping ligand octylamine (OLA) to replace the commonly used long ligand oleylamine (OAm). After the ligand modification, the photoluminescence quantum yield of CsPbBr3 QDs is enhanced from 62.4% to 91.3%. No aggregation or degradation phenomenon can be observed in solution even after being exposed to the air for 100 days. Moreover, the OLA‐CsPbBr3 QDs film can keep 96.8% of initial photoluminescence intensity even when stored under ambient condition for 5 weeks. Furthermore, the stimulated emission performance is investigated in terms of amplified spontaneous emission (ASE), and the ASE threshold of OLA‐CsPbBr3 QDs is only 24% of the OAm‐CsPbBr3 QDs threshold, and the ASE photostability is also enhanced. All the results suggest that the OLA ligand modification is an available strategy to improve the properties of CsPbBr3 QDs and to shed light on the potential practical applications for photoelectric devices.

Herein, we employed lead-free Cs3Cu2I5 perovskite films as the functional layers to construct Al/Cs3Cu2I5/ITO memory devices and systematically investigated the impact on the corresponding resistive switching (RS) performance via adding different amounts of hydroiodic acid (HI) in Cs3Cu2I5 precursor solution. The results demonstrated that the crystallinity and morphology of the Cs3Cu2I5 films can be improved and the resistive switching performance can be modulated by adding an appropriate amount of HI. The obtained Cs3Cu2I5 films by adding 5 μL HI exhibit the fewest lattice defects and flattest surface (RMS = 13.3 nm). Besides, the memory device, utilizing the optimized films, has a low electroforming voltage (1.44 V), a large on/off ratio (∼65), and a long retention time (104 s). The RS performance impacted by adding HI, providing a scientific strategy for improving the RS performance of iodine halide perovskite-based memories.

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In recent years, metal‐halide perovskite quantum dots (QDs) have been broadly applied in optoelectronic fields due to their fascinating characteristics, such as high photoluminescence quantum yields, tunable bandgaps, and low‐cost solution processing. Here, a facile ligand‐exchange strategy is employed for the fabrication of CsPbBr3 QDs capped with di‐dodecyl dimethyl ammonium bromide. It is demonstrated that the treated QDs' film becomes more compact with higher electron mobility and shorter lifetime. Besides, a reduced conduction band minimum value (0.28 eV) of perovskite QDs' film provides an efficient electron injection to them from ZnO nanoparticles. Through using the well‐passivated QDs' film, electroluminescence QD light‐emitting diode (QLED) devices with an indium tin oxide/ZnO/CsPbBr3 QDs/MoO3/4, 4′‐bis(carbazole‐9‐yl)biphenyl/Al inverted sandwich structure are achieved. The as‐prepared QLED device exhibits a maximum current efficiency of 0.62 cd A−1 and an external quantum efficiency of 0.58%, which is nearly nine times higher than that of the device based on unmodified QDs. More importantly, the stability testing results demonstrate that the QLED can be operated for more than 20 min under ambient conditions without any encapsulation. This provides an alternative route for highly efficient perovskite‐based LED with inverted sandwich structures.

Zero-dimensional (0D) perovskites are emerging as a class of optoelectronic materials due to their unprecedented strong excitonic properties and high stability. Although the photoluminescence properties of 0D perovskites (Cs 4 PbX 6 ) are investigated, the origin of green emission is still opaque, and their lasing performances are not reported. Herein, using the femtosecond transient absorption measurements to study the photophysical properties of Cs 4 PbBr 6 , the presence of polarons in Cs 4 PbBr 6 is revealed, which provides the evidence that the green emission is contributed from the intrinsic behavior of Cs 4 PbBr 6 rather than CsPbBr 3 impurities. The successful lasing achieved from Cs 4 PbBr 6 microdisks (MDs) by a room-temperature reverse microemulsion method is demonstrated. The as-prepared MDs with a smooth surface and a regular geometric structure can act as ideal whispering-gallery-mode microcavities. Optically pumped single-mode lasing with a low threshold and high-quality factor is successfully achieved from MDs under both one-and two-photon excitation at room temperature. The MDs display an excellent stability while stored under ambient conditions for several months. In addition, the phase transformation between CsPbBr 3 and Cs 4 PbBr 6 can be easily achieved via tuning the amounts of surfactants. This work suggests that 0D perovskites can be promising materials toward the development of miniaturized lasers and other optoelectronic devices.

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The growth and rupture of conductive filaments act a crucial part in the reliability of resistive switching behaviors. The random growth and rupture of conductive filaments are the primary reason for the instability of set/reset reproducibility. Hence, we propose a method that embedded carbon quantum dots (CQDs) in polymethylmethacrylate (PMMA) to fabricate the Ag/PMMA&CQDs/FTO resistive switching device. Five different concentrations of CQDs are embedded in PMMA to regulate the resistive switching properties, and the resistive memory characteristics of the optimal group are systematically studied. The optimal group exhibits excellent switching repeatability, low set/reset voltages, and stable forming voltage, which is much better than PMMA without CQDs. Furthermore, we employ the COMSOL software to build a simulation model for exploring the influence of CQDs on the internal electric field of PMMA, which proved that the introduction of CQDs might have a favorable effect on the orderly growth of conductive filaments.