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Emulation of photonic synapses through photo‐recordable devices has aroused tremendous discussion owing to the low energy consumption, high parallel, and fault‐tolerance in artificial neuromorphic networks. Nonvolatile flash‐type photomemory with short photo‐programming time, long‐term storage, and linear plasticity becomes the most promising candidate. Nevertheless, the systematic studies of mechanism behind the charge transfer process in photomemory are limited. Herein, the physical properties of APbBr3 perovskite quantum dots (PQDs) on the photoresponsive characteristics of derived poly(3‐hexylthiophene‐2,5‐diyl) (P3HT)/PQDs‐based photomemory through facile A‐site substitution approach are explored. Benefitting from the lowest valance band maximum and longest exciton lifetime of FAPbBr3 quantum dot (FA‐QDs), P3HT/FA‐QDs‐derived photomemory not only exhibits shortest photoresponsive characteristic time compared to FA0.5Cs0.5PbBr3 quantum dots (Mix‐QDs) and CsPbBr3 quantum dots (Cs‐QDs) but also displays excellent ON/OFF current ratio of 2.2 upon an extremely short illumination duration of 1 ms. Moreover, the device not only achieves linear plasticity of synapses by optical potentiation and electric depression, but also successfully emulates the features of photon synaptic such as pair‐pulse facilitation, long‐term plasticity, and multiple spike‐dependent plasticity and exhibits extremely low energy consumption of 3 × 10−17 J per synaptic event. [ABSTRACT FROM AUTHOR]

The development of potassium‐ion batteries (KIBs) relies on the exploration of stable layer‐structured oxide cathode materials and a comprehensive understanding of ion storage and diffusion behaviors. A multiphase riveting‐structured O3/P2/P3‐Na0.9[Ni0.3Mn0.55Cu0.1Ti0.05]O2 (Tri‐NMCT) is employed as cathode material for KIBs. It demonstrates an initial discharge specific capacity of 108 mA g−1 at current density of 15 mA g−1 in the voltage range of 1.5–4 V. Excellent cyclic stability is exhibited as well with a high 83% capacity retention after 600 cycles at a higher current density of 300 mA g−1. Based on the in‐situ XRD, it reveals that the P2 phase offers a more stable triangular prism site compared to the O3 phase. This stability inhibits the undesired phase transition from P3 to O3 during discharge, thereby ensuring the long‐term cyclic performance. Furthermore, Density of state (DOS) calculations and migration barrier analyses indicate a preferential migration of K+ ions to the P2 phase due to the lower Fermi level. This observation elucidates the structural preservation of the P3 phase during K+ embedding. Overall, this work sheds light on Tri‐NMCT as a promising cathode material for advanced KIBs. [ABSTRACT FROM AUTHOR]

Solution‐processable organic–inorganic hybrid perovskite materials have been applied to a variety of optoelectronic devices due to its long exciton lifetime and small binding energy. It has emerged as promising front‐runners for next‐generation non‐volatile flash photomemory devices. However, the effect of crystal orientation of perovskite on the performance of photomemory still has not fully developed. Herein, non‐volatile flash photomemory with quasi‐2D perovskite/polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) as photoactive floating‐gate and p‐type semiconductor poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) as the chare‐transporting layer is successfully demonstrated. By adding phenylethylammonium bromide (PEABr) in formamidinium lead bromide perovskite (FAPbBr3), the crystal orientation of quasi‐2D perovskite is highly improved, which results in raised charge transfer efficiency from 76% to 90% compared to the pure FAPbBr3. Furthermore, ON/OFF current ratio of 104, low photo‐programming time of 5 ms under light intensity of 0.85 mW cm−2, charge transfer rate of 0.063 ns−1, and data storage capacity of over 7 bits (128 levels) in one cell can be achieved. In addition, the correlation between photo‐responsive current and photoluminescence (PL) is first examined by in operando PL measurement, which provides a new platform to explore the charge transfer process in photomemory. [ABSTRACT FROM AUTHOR]

The exceptional properties of 2D transition metal carbides and nitrides (MXene) have led to numerous promising applications. However, the performance of MXene is often dependent on the size of the flakes, and obtaining large‐sized, high‐quality MXene flakes remains challenging. Herein, a carbon nanotube (CNT)‐assisted exfoliation strategy is introduced, which significantly improves the yield of large‐flake MXene while entirely transforming the centrifugation residues into small‐flake MXene, resulting in waste‐free synthesis of MXene. The average size of the obtained MXene flakes can reach over 10 and 0.7 µm for the two populations, respectively. Additionally, the capacitive performance of MXene can be greatly enhanced with a small amount of CNTs. As a proof of concept, a planar interdigital micro‐supercapacitor with heterogeneous layers assembled by large‐ and small‐flake MXene simultaneously exhibits outstanding synergistic enhancement in volumetric capacitance (1072 F cm⁻3) and energy density (53.5 mWh cm⁻3). This CNT‐assisted method provides explicit directions for achieving the ideal utilization of MXene, improving the yield of large flakes while making judicious use of waste, to meet specific application needs. [ABSTRACT FROM AUTHOR]

Toxic gases such as NO2 and irritant gases such as NH3 are two of the harshest aspects that trigger the exacerbation of the respiratory system for asthma patients. Monitoring and recording high‐risk gases are very important for tracking disease and alerting patients because humans can be exposed to a vulnerable environment with inconspicuous gases. Current detectors suffer from lack of portability and cannot provide daily real‐time detection. This work develops a light, inexpensive epidermal gas sensor based on ultralarge MoSe2 nanosheets. MoSe2 nanosheets are obtained using a gold‐assisted exfoliation method and the electrical and optical properties of the film are characterized. A high‐performance gas sensor for NO2 and NH3, which can be integrated onto human skin, is fabricated and shows great stability with up to 30% tensile strain. In particular, the device is able to detect down to 1 part per million with fast response (<200 s). The system is effective in providing timely warnings and the sensing data are uploaded to a cloud‐based terminal so that a medical institute can easily access them and provide a more accurate diagnosis. [ABSTRACT FROM AUTHOR]

Phosphorescent materials have received considerable attention in organic solar cells (OSCs) due to their long emission lifetime and inhibited geminate recombination. Motivated by its particular photophysical property, herein, the spatially addressable bis(2‐benzo[b]thiophen‐2‐ylpyridine)(acetylacetonate)iridium(III) (Ir(bt)2(acac))/polystyrene‐b‐poly(4‐vinylpyridine) (PS‐b‐P4VP) as a photoactive floating‐gate is first demonstrated to explore the application of phosphorescent material on the photo‐responsive characteristics of photomemory and artificial photonic synapse. By manipulating the interfacial area between Ir(bt)2(acac)/PS‐b‐P4VP and active channel by a solvent annealing process, an ON/OFF current ratio of 103 and a low programming time of 700 ms can be achieved. The current study addresses the exciton lifetime of photoactive material functions in photomemory and highlights the interfacial area between photoactive materials and charge‐carrier transporting materials in reducing photo‐programming time. [ABSTRACT FROM AUTHOR]

Ultrasmall silica‐based nanoparticles (SNPs) are attractive for application in many fields, but existing synthetic approaches show limited control over the size and morphology of these SNPs. This study describes a general single copolymer chain‐mediated strategy for the scalable synthesis of highly monodispersed symmetric and asymmetric SNPs with sub‐50 nm diameter. Random copolymers of poly(acrylic acid‐r‐styrene) intramolecularly collapse into ultrasmall single‐chain nanoparticles and serve as seeds to template the hydrolysis of silica precursors to produce uniform SNPs. It is shown in experiments and simulations that the composition and random architecture of the copolymers are crucial to the formation of ultrasmall seeds and the uniform deposition of silica. Furthermore, tailoring the architecture of copolymers can be used to produce ultrasmall asymmetric Janus‐like and dumbbell‐like SNPs with well‐defined polymer and silica domains. This study paves a new route to the scalable production of ultrasmall SNPs with tailored morphologies. [ABSTRACT FROM AUTHOR]

Narrowband photodetector (NB‐PD) with selective light detection is critical for artificial vision and imaging. Intrinsic (optical‐filter‐free) NB‐PDs using conjugated organics or halide perovskite materials have been developed for eliminating the current complex filtering systems in NB‐PDs. However, the poor performance and external driving circuit of organic NB‐PDs as well as complex doping and uncontrollable recombination reactions in typical perovskite NB‐PDs have limited their applicational diversification. A p‐type self‐doped perovskite for intrinsic NB detection is reported which exhibits unique unbalanced electron–hole transfer kinetics. In conjunction with the optical field distribution, an unbalanced charge transport within the self‐doped perovskite triggers a wavelength‐dependent photo‐carrier collection, resulting in a novel spontaneous internal quantum efficiency narrowing mechanism. As a result, by reverting the device architectural polarity, an NB detection at a monochromic light of either red or UV is observed. Using such a revertible asymmetric device design, self‐powered NB‐PDs are successfully achieved. Briefly, the corresponding NB‐PDs exhibit excellent narrow response with a response window of ≈100 nm, high detectivity ≈1011 Jones, and fast response speed (f−3dB ≈ 60 kHz) at zero bias. These results demonstrate a new strategy of manipulating internal charge transport to realize power‐free and filter‐free intrinsic NB‐PDs. [ABSTRACT FROM AUTHOR]

With the power conversion efficiencies of perovskite solar cells (PSCs) exceeding 25%, the PSCs are a step closer to initial industrialization. Prior to transferring from laboratory fabrication to industrial manufacturing, issues such as scalability, material cost, and production line compatibility that significantly impact the manufacturing remain to be addressed. Here, breakthroughs on all these fronts are reported. Carbon‐based PSCs with architecture fluorine doped tin oxide (FTO)/electron transport layer/perovskite/carbon, that eliminate the need for the hole transport layer and noble metal electrode, provide ultralow‐cost configuration. This PSC architecture is manufactured using a scalable and industrially compatible electrospray (ES) technique, which enables continuous printing of all the cell layers. The ES deposited electron transport layer and perovskite layer exhibit properties comparable to that of the laboratory‐scale spin coating method. The ES deposited carbon electrode layer exhibits superior conductivity and interfacial microstructure in comparison to films synthesized using the conventional doctor blading technique. As a result, the fully ES printed carbon‐based PSCs show a record 14.41% power conversion efficiency, rivaling the state‐of‐the‐art hole transporter‐free PSCs. These results will immediately have an impact on the scalable production of PSCs. [ABSTRACT FROM AUTHOR]

Multijunction/tandem solar cells have naturally attracted great attention because they are not subject to the Shockley–Queisser limit. Perovskite solar cells are ideal candidates for the top cell in multijunction/tandem devices due to the high power conversion efficiency (PCE) and relatively low voltage loss. Herein, sandwiched gold nanomesh between MoO3 layers is designed as a transparent electrode. The large surface tension of MoO3 effectively improves wettability for gold, resulting in Frank–van der Merwe growth to produce an ultrathin gold nanomesh layer, which guarantees not only excellent conductivity but also great optical transparency, which is particularly important for a multijunction/tandem solar cell. The top MoO3 layer reduces the reflection at the gold layer to further increase light transmission. As a result, the semitransparent perovskite cell shows an 18.3% efficiency, the highest reported for this type of device. When the semitransparent perovskite device is mechanically stacked with a heterojunction silicon solar cell of 23.3% PCE, it yields a combined efficiency of 27.0%, higher than those of both the sub‐cells. This breakthrough in elevating the efficiency of semitransparent and multijunction/tandem devices can help to break the Shockley–Queisser limit. [ABSTRACT FROM AUTHOR]

In article number 1804419, Congcong Wu, Shashank Priya, and co‐workers develope a dual‐functional PMMA‐fullerene complex, where the fullerene C60 dwells in the caves of the PMMA polymer chain. The PMMA‐fullerene complex is incorporated into the perovskite layer, which resides along the grain boundary of the perovskites. The fullerene reduces the charge carrier recombination and the PMMA polymer improves the stability of the perovskite solar cell. [ABSTRACT FROM AUTHOR]

Lead halide perovskite solar cells (PSCs) have demonstrated great potential for realizing low‐cost and easily fabricated photovoltaics. At this juncture, power conversion efficiency and long‐term stability are two important factors limiting their transition. PSCs exhibit rapid environmental degradation since the perovskite layer is very sensitive to factors such as humidity, temperature, and ultraviolet light. Here, a novel successful approach is demonstrated that simultaneously improves the efficiency and stability of PSCs. This approach relies on incorporation of a dual‐functional polymethyl methacrylate (PMMA)–fullerene complex into the perovskite layer. The fullerene within perovskite layer forms a localized dipole‐like electric field that favors electron–hole separation, resulting in significant improvement in current density and fill factor with conversion efficiency reaching 18.4%. The molecular‐scale coating of hydrophobic PMMA on the perovskite grain boundary effectively blocks moisture penetration into the perovskite, thereby, significantly improving the stability against moisture, heat, and light. The PSCs with PMMA–fullerene complex showed no photovoltaic performance degradation for 250 d and exhibited 60 times higher stability compared to the state‐of‐the‐art devices under continuous 1 sun illumination in ambient air. Polymethyl methacrylate is coated on a perovskite grain boundary, blocking moisture penetration. The distributed C60 clusters create a dipole‐like electric field inside the perovskite layer, which favors exciton dissociation, and improves the conversion efficiency of perovskite solar cells. [ABSTRACT FROM AUTHOR]