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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