Due to the exciting photoelectric properties, better stability, and environmental-friendly nature, all-inorganic halide perovskites (AIHPs), especially the lead-free perovskites, have attracted worldwide attention. However, the film quality of AIHPs fabricated by typical spin-coating and subsequent high-temperature annealing is still not satisfactory, restricting their further development. Herein, we demonstrate a simple low-temperature solution-processed drop-casting method to achieve highly-crystalline cubic CsPbBr₃ and lead-free layer-structured Cs₃Sb₂I₉ microcrystals (MCs). This drop-casting technique not only consumes the less amount of precursor solution but also eliminates the high-temperature annealing as compared with those of spin coating. When these MCs are configured into photodetectors, they exhibit superior device performance, which is in distinct contrast to the one of spin-coated counterparts. Specifically, the responsivity of CsPbBr₃ MCs is found to be as large as 8,990 mA/W, being 13 times larger than the spin-coated films and even better than many state-of-the-art solution-processed AIHPs devices. This device performance enhancement is attributed to the better film quality and phase purity obtained by the drop-casting method. All these results can evidently fill the “technology gap” for further enhancing the material quality of solution-processed AIHPs and breaking down the barriers that hinder the development of AIHPs based optoelectronic devices.

Hybrid organolead halide perovskites have attracted tremendous attention due to their recent success as high efficiency solar cell materials and their fascinating material properties uniquely suitable for optoelectronic devices. However, the poor ambient and operational stability as well as the concern of lead toxicity greatly hamper their practical utilization. In this work, crystalline, all-inorganic and lead-free Cs₃Sb₂I₉ perovskite microplates are successfully synthesized by a two-step chemical vapor deposition method. As compared with other typical lead-free perovskite materials, the Cs₃Sb₂I₉ microplates demonstrate excellent optoelectronic properties, including substantial enhancements in the Stokes shift, exciton binding energy and electron-phonon coupling. Simple photoconductive devices fabricated using these microplates exhibit an ultra-fast response with the rise and decay time constants down to 96 and 58 μs, respectively. This respectable photoconductor performance can be regarded as a record among all the lead-free perovskite materials. Importantly, these photodetectors show superior thermal stability in a wide temperature range, capable to function reversibly between 80 and 380 K, indicating their robustness to operate under both low and high temperatures. All these results evidently suggest the technological potential of inorganic lead-free Cs₃Sb₂I₉ perovskite microplates for next-generation high-performance optoelectronic devices.

Due to the enhanced ambient structural stability and excellent optoelectronic properties, all-inorganic metal halide perovskite nanowires have become one of the most attractive candidates for flexible electronics, photovoltaics and optoelectronics. Their elastic property and mechanical robustness become the key factors for device applications under realistic service conditions with various mechanical loadings. Here, we demonstrate that high tensile elastic strain (~ 4% to ~ 5.1%) can be achieved in vapor-liquid-solid-grown single-crystalline CsPbBr₃ nanowires through in situ scanning electron microscope (SEM) buckling experiments. Such high flexural elasticity can be attributed to the structural defect-scarce, smooth surface, single-crystallinity and nanomechanical size effect of CsPbBr₃ nanowires. The mechanical reliability of CsPbBr₃ nanowire- based flexible photodetectors was examined by cyclic bending tests, with no noticeable performance deterioration observed after 5, 000 cycles. The above results suggest great application potential for using all-inorganic perovskite nanowires in flexible electronics and energy harvesting systems.

Due to the ultra-thin nature and moderate carrier mobility, semiconducting two-dimensional (2D) materials have attracted extensive attention for next-generation electronics. However, the gate bias stress instability and hysteresis are always observed in these 2D materials-based transistors that significantly degrade their reliability for practical applications. Herein, the origin of gate bias stress instability and hysteresis for chemical vapor deposited monolayer WS₂ transistors are investigated carefully. The transistor performance is found to be strongly affected by the gate bias stress time, sweeping rate and range, and temperature. Based on the systematical study and complementary analysis, charge trapping is determined to be the major contribution for these observed phenomena. Importantly, due to these charge trapping effects, the channel current is observed to decrease with time; hence, a rate equation, considering the charge trapping and time decay effect of current, is proposed and developed to model the phenomena with excellent consistency with experimental data. All these results do not only indicate the validity of the charge trapping model, but also confirm the hysteresis being indeed caused by charge trapping. Evidently, this simple model provides a sufficient explanation for the charge trapping induced gate bias stress instability and hysteresis in monolayer WS₂ transistors, which can be also applicable to other kinds of transistors.

Designing highly efficient and low-cost electrocatalysts for oxygen evolution reaction is important for many renewable energy applications. In particular, strain engineering has been demonstrated as a powerful strategy to enhance the electrochemical performance of catalysts; however, the required complex catalyst preparation process restricts the implementation of strain engineering. Herein, we report a simple self-template method to prepare hierarchical porous Co₃O₄ nanowires (PNWs) with tunable compressive strain via thermal-oxidation-transformation of easily prepared oxalic acid-cobalt nitrate (Co(NO₃)₂) composite nanowires. Based on the complementary theoretical and experimental studies, the selection of proper solvents in the catalyst preparation is not only vital for the hierarchical structural evolution of Co₃O₄ but also for regulating their compressive surface strain. Because of the rich surface active sites and optimized electronic Co d band centers, the PNWs exhibit the excellent activity and stability for oxygen evolution reaction, delivering a low overpotential of 319 mV at 10 mA·cm^-2 in 1 M KOH with a mass loading 0.553 mg·cm^-2, which is even better than the noble metal catalyst of RuO₂. This work provides a cost-effective example of porous Co₃O₄ nanowire preparation as well as a promising method for modification of surface strain for the enhanced electrochemical performance.

Amorphous indium–gallium–zinc oxide (a-IGZO) materials have been widely explored for various thin-film transistor (TFT) applications; however, their device performance is still restricted by the intrinsic material issues especially due to their non-crystalline nature. In this study, highly crystalline superlattice-structured IGZO nanowires (NWs) with different Ga concentration are successfully fabricated by enhanced ambient-pressure chemical vapor deposition (CVD). The unique superlattice structure together with the optimal Ga concentration (i.e., 31 at.%) are found to effectively modulate the carrier concentration as well as efficiently suppress the oxygen vacancy formation for the superior NW device performance. In specific, the In_1.8Ga_1.8Zn_2.4O₇ NW field-effect transistor exhibit impressive device characteristics with the average electron mobility of ~ 110 cm²·V⁻¹·s⁻¹ and on/off current ratio of ~ 10⁶. Importantly, these NWs can also be integrated into NW parallel arrays for the construction of high-performance TFT devices, in which their performance is comparable to many state-of-the-art IGZO TFTs. All these results can evidently indicate the promising potential of these crystalline superlattice-structured IGZO NWs for the practical utilization in next-generation metal-oxide TFT device technologies.

Recently, owing to the excellent electrical and optical properties, n-type In₂O₃ nanowires (NWs) have attracted tremendous attention for application in memory devices, solar cells, and ultra-violet photodetectors. However, the relatively low electron mobility of In₂O₃ NWs grown by chemical vapor deposition (CVD) has limited their further utilization. In this study, utilizing in-situ Ga alloying, highly crystalline, uniform, and thin In_2xGa_2-2xO₃ NWs with diameters down to 30 nm were successfully prepared via ambient-pressure CVD. Introducing an optimal amount of Ga (10 at.%) into the In₂O₃ lattice was found to effectively enhance the crystal quality and reduce the number of oxygen vacancies in the NWs. A further increase in the Ga concentration adversely induced the formation of a resistive β-Ga₂O₃ phase, thereby deteriorating the electrical properties of the NWs. Importantly, when configured into global back-gated NW field-effect transistors, the optimized In_1.8Ga_0.2O₃ NWs exhibit significantly enhanced electron mobility reaching up to 750 cm²·V^–1·s^–1 as compared with that of the pure In₂O₃ NW, which can be attributed to the reduction in the number of oxygen vacancies and ionized impurity scattering centers. Highly ordered NW parallel arrayed devices were also fabricated to demonstrate the versatility and potency of these NWs for next-generation, large-scale, and high-performance nanoelectronics, sensors, etc.

Two-dimensional (2D) nanomaterials have recently attracted considerable attention due to their promising applications in next-generation electronics and optoelectronics. In particular, the large-scale synthesis of high-quality 2D materials is an essential requirement for their practical applications. Herein, we demonstrate the wafer-scale synthesis of highly crystalline and homogeneous monolayer WS₂ by an enhanced chemical vapor deposition (CVD) approach, in which precise control of the precursor vapor pressure can be effectively achieved in a multi-temperature zone horizontal furnace. In contrast to conventional synthesis methods, the obtained monolayer WS₂ has excellent uniformity both in terms of crystallinity and morphology across the entire substrate wafer grown (e.g., 2 inches in diameter), as corroborated by the detailed characterization. When incorporated in typical rigid photodetectors, the monolayer WS₂ leads to a respectable photodetection performance, with a responsivity of 0.52 mA/W, a detectivity of 4.9 × 10⁹ Jones, and a fast response speed (< 560 μs). Moreover, once fabricated as flexible photodetectors on polyimide, the monolayer WS₂ leads to a responsivity of up to 5 mA/W. Importantly, the photocurrent maintains 89% of its initial value even after 3, 000 bending cycles. These results highlight the versatility of the present technique, which allows its applications in larger substrates, as well as the excellent mechanical flexibility and robustness of the CVD-grown, homogenous WS₂ monolayers, which can promote the development of advanced flexible optoelectronic devices.

Although In₂O₃ nanofibers (NFs) are well-known candidates as active materials for next-generation, low-cost electronics, these NF based devices still suffer from high leakage current, insufficient on–off current ratios (I_on/I_off), and large, negative threshold voltages (V_TH), leading to poor device performance, parasitic energy consumption, and rather complicated circuit design. Here, instead of the conventional surface modification of In₂O₃ NFs, we present a one-step electrospinning process (i.e., without hot-press) to obtain controllable Mg-doped In₂O₃ NF networks to achieve high-performance enhancement-mode thin-film transistors (TFTs). By simply adjusting the Mg doping concentration, the device performance can be manipulated precisely. For the optimal doping concentration of 2 mol%, the devices exhibit a small V_TH (3.2 V), high saturation current (1.1 × 10^–4 A), large on/off current ratio (> 10⁸), and respectable peak carrier mobility (2.04 cm²/(V·s)), corresponding to one of the best device performances among all 1D metal-oxide NFs based devices reported so far. When high-κ HfO_x thin films are employed as the gate dielectric, their electron mobility and V_TH can be further improved to 5.30 cm²/(V·s) and 0.9 V, respectively, which demonstrates the promising prospect of these Mg-doped In₂O₃ NF networks for highperformance, large-scale, and low-power electronics.