Flexible Piezoelectric Nanocomposite Generators Based on Formamidinium Lead Halide Perovskite Nanoparticles

Organic–inorganic lead halide perovskite materials have recently attracted much attention in the field of optoelectronic devices. Here, a hybrid piezoelectric nanogenerator based on a composite of piezoelectric formamidinium lead halide perovskite (FAPbBr₃) nanoparticles and polydimethylsiloxane polymer is fabricated. Piezoresponse force spectroscopy measurements reveal that the FAPbBr₃ nanoparticles contain well‐developed ferroelectric properties with high piezoelectric charge coefficient (d₃₃) of 25 pmV⁻¹. The flexible device exhibits high performance with a maximum recordable piezoelectric output voltage of 8.5 V and current density of 3.8 μA cm⁻² under periodically vertical compression and release operations. The alternating energy generated from nanogenerators can be used to charge a capacitor and light up a red light‐emitting diode through a bridge rectifier. This result innovatively expands the feasibility of organic–inorganic lead halide perovskite materials for application in a wide variety of high‐performance energy harvesting devices.     

All-Inorganic CsPbBr3 Perovskite Nanocrystals/2D Non-Layered Cadmium Sulfide Selenide for High-Performance Photodetectors by Energy Band Alignment Engineering

Perovskites have attracted intensive attention as promising materials for the application in various optoelectronic devices due to their large light absorption coefficient, high carrier mobility, and long charge carrier diffusion length. However, the performance of the pure perovskite nanocrystals-based device is extremely restricted by the limited charge transport capability due to the existence of a large number of the grain boundary between perovskite nanocrystals. To address these issues, a high-performance photodetector based on all-inorganic CsPbBr₃ perovskite nanocrystals/2D non-layered cadmium sulfide selenide heterostructure has been demonstrated through energy band engineering with designed typed-II heterostructure. The photodetector exhibits an ultra-high light-to-dark current ratio of 1.36 × 10⁵, a high responsivity of 2.89 × 10² A W⁻¹, a large detectivity of 1.28 × 10¹⁴ Jones, and the response/recovery time of 0.53s/0.62 s. The enhancement of the optoelectronic performance of the heterostructure photodetector is mainly attributed to the efficient charge carrier transfer ability between the all-inorganic CsPbBr₃ perovskites and 2D cadmium sulfide selenide resulting from energy band alignment engineering. The charge carriers’ transfer dynamics and the mechanism of the CsPbBr₃ perovskites/2D non-layered nanosheets interfaces have also been studied by state-state PL spectra, fluorescence lifetime imaging microscopy, time-resolved photoluminescence spectroscopy, and Kelvin probe force microscopy measurements.     

Epitaxial Growth of Large‐Scale Orthorhombic CsPbBr3 Perovskite Thin Films with Anisotropic Photoresponse Property

Inorganic cesium lead halide perovskite (CsPbX₃, X = Cl, Br, I) is a promising material for developing novel electronic and optoelectronic devices. Despite the substantial progress that has been made in the development of large perovskite single crystals, the fabrication of high‐quality 2D perovskite single‐crystal films, especially perovskite with a low symmetry, still remains a challenge. Herein, large‐scale orthorhombic CsPbBr₃ single‐crystal thin films on zinc‐blende ZnSe crystals are synthesized via vapor‐phase epitaxy. Structural characterizations reveal a “CsPbBr₃(110)//ZnSe(100), CsPbBr₃[?110]//ZnSe[001] and CsPbBr₃[001]//ZnSe[010]” heteroepitaxial relationship between the covering CsPbBr₃ layer and the ZnSe growth substrate. It is exciting that the epitaxial film presents an in‐plane anisotropic absorption property from 350 to 535 nm and polarization‐dependent photoluminescence. Photodetectors based on the epitaxial film exhibit a high photoresponsivity of 200 A W^?1, a large on/off current ratio exceeding 10⁴, a fast photoresponse time of about 20 ms, and good repeatability at room temperature. Importantly, a strong polarization‐dependent photoresponse is also found on the device fabricated using the epitaxial CsPbBr₃ film, making the orthorhombic perovskite promising building blocks for optoelectronic devices featured with anisotropy.     

基于1-3压电复合材料的相控聚焦系统

针对相控聚焦超声系统控制电路复杂、移相精度低, 锆钛酸铅(PZT)材料制备的换能器转换效率较低的问题。控制电路采用Verilog HDL语言将通信、倍频锁相、信号发生及信号移相功能集成在现场可编程门阵列(FPGA)中。换能器采用1-3型压电复合材料制作。实验结果显示,该相控聚焦系统提高了电路集成度与移相精度及换能器的电声转换效率。     

基于1-3压电复合材料的透镜式聚焦换能器设计

为了抑制压电陶瓷透镜式聚焦换能器振动的多模耦合现象,提高换能器电声转换效率,采用1-3压电复合材料,设计了一种新型的透镜式聚焦换能器;首先计算并仿真了1-3压电复合材料的厚度谐振频率ft和厚度机电耦合系数kt,理论和仿真结果分别相差2.947％和0.933％;接着对换能器做振动分析,结果表明,在换能器谐振频率ft处,声透镜中心径向振幅仅为厚度振幅的7.9％,径向振动得到有效抑制,这有助于提高换能器电声转换效率.     

Meeting High Stability and Efficiency in Hybrid Light‐Emitting Diodes Based on SiO2/ZrO2 Coated CsPbBr3 Perovskite Nanocrystals

Significant advances are realized in perovskite‐converted hybrid light‐emitting diodes (pc‐HLEDs). However, long‐living devices at high efficiencies still represent a major milestone with average stabilities of < 200 h at ≈ 50 lm W^?1 under low applied currents ( < 15 mA). Herein, a dual metal oxide‐coated CsPbBr₃@SiO₂/ZrO₂ composite is prepared in a one‐pot synthesis through the kinetic control of the sol–gel reaction, followed by a gentle drying process in air. These hybrid nanoparticles show photoluminescence quantum yields of ≈ 65% that are stable under temperature, ambient, and irradiation stress scenarios. This is translated to pc‐HLEDs with a near‐unity conversion efficiency at any applied current, high efficiencies around 75 lm W^?1, and one of the most remarkable stabilities of ≈ 200 and 700 h at 100 and 10 mA, respectively. In addition, the device degradation mechanism is thoughtfully rationalized comparing devices operating under ambient/inert conditions. As such, this work provides three milestones: i) a new room temperature one‐pot protocol to realize the first SiO₂/ZrO₂ metal oxide coating that effectively protects the emitting perovskite nanoparticle core, ii) one of the most stable and efficient pc‐HLEDs operating under ambient condition at any applied current, and iii) new insights for the degradation of pc‐HLEDs.     

CsPbBr3:Na with an Adjustable Bandgap,Improved Luminescence Stability,and its Application in WLEDs with Excellent Color Quality and Vision Performance

It is still a great challenge to obtain multicolor tunable luminescence and improve the stability of luminescence through reasonable design of materials in the field of white light-emitting diodes (WLEDs). In particular, it is more important to improve the luminescence intensity and stability of blue-emitting materials. Here, the properties of CsPbBr₃, CsPbBr₃:Na_, and NaPbBr₃ are investigated theoretically by using density functional theory (DFT). Based on the DFT theoretical calculation results, it is assumed that unexpected performance may be achieved by replacing Cs in CsPbBr₃ with Na or passivating the surface of CsPbBr₃ with Na. As expected, the tunable luminescence from blue to green is successfully achieved from CsPbBr₃:Na, and the stability is improved. After experimental optimization, the obtained CsPbBr₃:Na (CPBN-4) with high luminescence stability is used as blue-emitting materials to construct the WLED devices with excellent color quality (CRI 92) and correlated color temperature of 9582 K.     

Sustainable Nanotextured Wave Energy Harvester Based on Ferroelectric Fatigue‐Free and Flexoelectricity‐Enhanced Piezoelectric P(VDF‐TrFE) Nanofibers with BaSrTiO3 Nanoparticles

Here, ultrathin, flexible, and sustainable nanofiber‐based piezoelectric nanogenerators (NF‐PENGs) are fabricated and applied as wave energy harvesters. The NF‐PENGs are composed of poly(vinylidene fluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) nanofibers with embedded barium strontium titanate (BaSrTiO₃) nanoparticles, which are fabricated by using facile, scalable, and cost‐effective fiber‐forming methods, including electrospinning and solution blowing. The inclusion of ferroelectric BaSrTiO₃ nanoparticles inside the electrospun P(VDF‐TrFE) nanofibers enhances the sustainability of the NF‐PENGs and results in unique flexoelectricity‐enhanced piezoelectric nanofibers. Not only do these NF‐PENGs yield a superior performance compared to the previously reported NF‐PENGs, but they also exhibit an outstanding durability in terms of mechanical properties and cyclability. Furthermore, a new theoretical estimate of the energy harvesting efficiency from the water waves is introduced here, which can also be employed in future studies associated with various nanogenerators, including PENGs and triboelectric nanogenerators.