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The cutting temperature plays an important role in the machining process. Research on the real-time monitoring of cutting temperature and its effect on tool wear still faces many challenges. In this paper, a fiber-optic two-color pyrometer is proposed to obtain temperature of cutting edge during turning at real-time. The effects of the cutting speed, cutting depth and feed rate on the variation of cutting edge temperatures are investigated. Intermittent cutting experiments are performed to verify the effectiveness and dynamic responsiveness. The processed inserts show good durability. The cutting temperature change and its effect on tool wear are also investigated.

Perovskite photodetectors, with the merits of excellent light absorption, high carrier mobility and fast light response, are attracting tremendous interest for their promising application in optical communication, sensing and imaging. However, the requirement of a power supply for photoconductive detectors or the usage of expensive charge transport layers for photovoltaic detectors will pronouncedly increase the whole costs and process complexity. Herein, we demonstrate a self-powered inorganic perovskite photodetector with a novel and simplified configuration of ITO/CsPbBr3/Ag. Since no electron and hole transport layers are employed, it is highly necessary for the CsPbBr3 layer to prevent direct contact between the anode and cathode. Hence, we develop a sequential evaporation technique to fabricate a high-quality CsPbBr3 photosensitive film, which is more controllable than the traditional solution-processing route. The evaporated CsPbBr3 film obtains a much higher crystallinity, phase-purity, coverage and light harvesting capability than the conventionally solution-processed counterparts. The evaporated CsPbBr3 also exhibits larger grain sizes with fewer grain boundaries, enabling a faster charge transport and shorter photoresponse time of 54 ms for the photodetectors. After modification by a thin polymethyl methacrylate (PMMA) layer, the trap states and leakage current pathways in the CsPbBr3 film are substantially decreased, yielding an improved carrier lifetime and suppressed recombination loss. The PMMA-modified photodetectors achieve an ultrafast response time of 3.8 μs and an ultrahigh on/off ratio of 3.5 × 104, which are the best performance among all the reported charge-transport-layer-free perovskite photodetectors and surpass most of the perovskite photodetectors even with charge transport layers. The as-fabricated CsPbBr3 detectors also present superior stability after being stored in ambient air for over 1000 h. Moreover, our devices are successfully applied in a home-made visible light communication system as light receivers to transmit audio signals. Our work solves the contradiction between high detection performance and structure simplification, promoting practical applications of cost-effective, ultrafast and stable inorganic perovskite photodetectors in the optoelectronic field.

Organic–inorganic halide perovskite materials exhibit excellent memristive properties, such as high ON/OFF ratio and low switching voltage. However, the toxicity of lead and poor stability strictly limit their further commercial applications. Herein, a high-quality nontoxic and stable AgBiI4 perovskite film is successfully synthesized via a low-temperature dynamic hot casting method, and resistive switching (RS) memory devices based on AgBiI4 are reported for the first time. The RS memory devices with the ITO substrate exhibit typical bipolar nonvolatile memory behaviors with an ultralow operating voltage (≈0.16 V), high ON/OFF ratio (≈104), reversible RS by pulse voltage operation (>700) and long data retention (>104 s), superior to those of most of the other perovskite-based memory devices. Furthermore, a high performance flexible nonvolatile resistive switching (RS) memory device based on a AgBiI4 perovskite with a PEN substrate is fabricated. The flexible device also displays good stability under repeated bending tests (>1000 cycles). By analyzing the current–voltage responses, and the transmission electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy results, we propose a mechanism involving conducting filaments formed by Ag cations to describe the RS behavior of the Ag/PMMA/AgBiI4/ITO device. Our work demonstrates that AgBiI4 is promising for nonvolatile memory devices and paves the way for realizing low-power consumption flexible nonvolatile memory devices.

Humidity sensors have attracted intense interest in various fields because of the importance of humidity detection. Different methods have been adopted to enhance sensing performances of humidity s...

Carbon-based perovskite solar cells aroused huge attention for their simple, low-cost device fabrication processing and excellent stability. However, the fully low-temperature preparation and flexibility of carbon-based perovskite solar cells remain huge challenges. Here we demonstrate the fabrication of carbon-based perovskite solar cells processed at fully low-temperature, which take thermally evaporated cadmium sulfide as efficient electron transport layer, and obtain an optimal power conversion efficiency of 13.22%. With the decoration of PCBM, the separation of charges at the interface is facilitated and the recombination is hindered, so a higher fill factor is obtained and the efficiency is further improved to 14.28%. Our devices also exhibit good long-term durability and excellent ultraviolet stability. Based on the fully low-temperature preparation process, carbon-based flexible devices are further developed with an optimal efficiency over 9% and considerable mechanical stability, which can serve as the roof-top photovoltaics and power sources for wearable devices.

Atomically thin MoS2 film has displayed great potential for future optoelectronics due to its outstanding photonic and electronic properties. However, many important applications, especially for photodetection, are still severely limited by its low light absorption. In this paper, we demonstrate a high-performance photodetector based on perovskite/MoS2 hybrid film, which exhibits sensitive, fast, and stable response under low operation potential. The external photoresponsivity is about 342 A/W at bias potential of 2 V without gate voltage under incident power of 2.2 pW (520 nm), which is superior than most of the photodetectors based on transition metal dichalcogenides and perovskite. The devices show high stability during transient on/off test without any encapsulation, in which the response and recovery time has been recorded as 27 ms and 21 ms, respectively. Besides, the devices can be fabricated on various substrates, including SiO2/Si, transparent glass and flexible PET, etc. The flexible perovskite/MoS2 photodetectors with ultrahigh stability during 20,000 times bending was reported for the first time. We expect the proposed hybrid photodetector would be a competitive candidate in future flexible electronics. Our research also paves the way to integrate various atomically thin films with highly optical absorption materials.

Organic-inorganic lead halide perovskite solar cells have garnered enormous interest in scientific communities due to comparable power conversion efficiencies and solution-processed fabrication techniques. Among them, carbon-based perovskite solar cells seem to be one of the most promising candidates for addressing the stability issue while suffering from inferior efficiency or high processing temperature. Herein, we introduce low-temperature processed Zn-doped SnO2 (below 200 °C) as an effective electron transport layer in perovskite solar cells for the first time, and demonstrate a low-temperature carbon-based device with Cu-phthalocyanine as hole transport layer. We find that Zn doping contributes to a more suitable energy level alignment and an improved conductivity for SnO2 films. As a result, the electron transfer and extraction are enhanced and the charge recombination is suppressed. In addition, devices with Zn-doped SnO2 have a wider depletion region, leading to an enhanced photovoltaic performance. An optimal efficiency of 17.78% can be obtained after 2 mM Zn doping. Furthermore, these devices, introducing highly stable and hydrophobic Cu-phthalocyanine and carbon, maintain almost 100% of their initial efficiencies over 1200 h in ambient air. Our study paves the way for developing highly efficient and flexible carbon-based perovskite solar cells.

Fabrication of carbon micro/nanostructures by carbon microelectromechanical systems (carbon-MEMS) technique on conductive substrate stably is of great significance but difficulty, for the poor adhesive property and low -temperature resistance of the substrate. In this study, three-dimensional carbon micro/nanostructures are fabricated on stainless steel (SS) substrate for the first time by carbon-MEMS technique and oxygen plasma etching process without extra conductive layer fabrication process. The effects of oxygen plasma etching time and the height of photoresist array on the morphologies of carbon micro/nanostructures are investigated. The carbon micro/nanostructures were then electrodeposited with manganese dioxide (MnO2) thin film as microelectrodes for supercapacitors, and the electrochemical performances of the microelectrodes were demonstrated. At the current density of 0.05 mA cm−2, the MnO2/carbon micro/nanostructures microelectrode deposited with 5 min show a large specific capacitance of 453.47 F g−1. It also shows excellent long-term cycling stability of ∼94% capacitance retention even after 6000 cycling tests. This study shows that the MnO2/carbon micro/nanostructures microelectrodes have great potential for supercapacitors as micro-energy storage devices, and the proposed approach of fabricating carbon hierarchical micro/nanostructures array on a conductive substrate is promising for large-scale micro/nanostructures manufacturing.

All-inorganic CsPbBr3 perovskite solar cells (PSCs) have attracted tremendous attentions in the photovoltaic field these days in view of their outstanding stability, especially thermal stability. However, the bromide-rich perovskite, such as CsPbBr3, always suffer from a low phase-purity and poor morphology synthesized by traditional two-step deposition route. Herein, we demonstrate a facile multistep spin-coating strategy to fabricate high-quality CsPbBr3 films on the low-temperature processed compact TiO2 (c-TiO2) electron transport layer (ETL) of the carbon-based PSCs. As-prepared films exhibit more homogeneous with higher CsPbBr3-phase purity and larger average grain sizes up to 1 µm, compared to those prepared through traditional two-step deposition process. The champion power conversion efficiency (PCE) of the planar CsPbBr3 PSC is boosted from 7.05% to 8.12%, getting an increase by 15.2%, due to the increased crystallinity and light-harvesting ability as well as reduced trap states of the CsPbBr3 film. To further enhance the device performance, a SnO2 thin layer with much higher carrier mobility than TiO2 is introduced to passivate the c-TiO2 ETL. It is found that the SnO2 layer can not only improve the surface morphology of the ETL, but also reduce the current shunting pathways in the c-TiO2. The TiO2/SnO2 bilayered ETL possesses a superior electron extraction capability, beneficial to the charge transport and suppression of the interfacial trap-assisted recombination. The best-performing TiO2/SnO2-based CsPbBr3 PSC delivers an excellent fill factor of 0.817 and a high PCE of 8.79%, which is the highest efficiency for planar CsPbBr3 PSCs reported to date. More importantly, the unencapsulated all-inorganic PSCs show a promising humidity and thermal stability with no decline in efficiency when stored in ambient air at room temperature (25 °C) for over 1000 h and 60 °C for one month, respectively. Our work pave the ways for practical applications of cost-effective, highly efficient and stable all-inorganic PSCs.

The accurate and reliable measurement of humidity is of great importance in various applications. It is challenging for researchers to pursue a humidity sensor with high performance and detection ability, especially when the device is wet. Here, we present a strategy involving the in situ growth of superhydrophilic Cu(OH)2 nanowires on a quartz crystal microbalance as a sensing layer through one-step alkali-assisted surface oxidation for the first time. The nanowires not only possessed numerous hydroxyl radicals for absorbing moisture but also exhibited superhydrophilicity, endowing the device with self-evaporation property after being wet (named as self-healing ability). We found that the Cu(OH)2 nanowire devices exhibited high sensitivity (85.9 Hz/%RH) and a rapid recovery speed (1.9 s). In particular, the devices could restore 91.8% sensitivity after being wet for 100 cycles, demonstrating excellent self-healing ability. The moisture of proximal fingertips and the mouth/nose breath of humans could be sensitively detected by the sensor, showing its potential in multifarious applications. In addition, density functional theory simulations combined with Fourier transform infrared spectroscopy experiments were carried out to study the adsorption of H2O on Cu(OH)2 surfaces, and the sensing mechanism was revealed. Our work highlights the unique advantage of superhydrophilic Cu(OH)2 nanowires for humidity detection with self-healing ability, and it also opens up a new application area for superhydrophilic materials.

Water collection has been extensively researched due to its potential for mitigating the water scarcity in arid and semiarid regions. Numerous structures mimicking the fog-harvesting strategy of organisms have been fabricated for improving water-collecting efficiency. In this contribution, we demonstrate four-level wedge-shaped tracks inspired by leaf vein for enhancing directional water collection. Superhydrophilic Cu(OH)2 nanowires are introduced and prepared on flexible hydrophobic polyethylene terephthalate (PET) substrates by alkali-assisted surface oxidation at room temperature. They provide abundant capillary paths for promoting droplet absorption and forming water film tracks. Then, the hierarchical wedge-shaped tracks enable the water to be transported to a certain accumulation region spontaneously owing to the continuous Young–Laplace pressure difference. As a result, the four-level wedge-shaped tracks on PET substrate achieve the highest water-collecting efficiency, increasing by nearly 1150 an...

The rapid development of flexible electronics and artificial intelligence brings an urgent demand for high-performance flexible pressure sensors. In this paper, a method is proposed to prepare wrinkled graphene foam by freeze-drying and post-annealing method, where zinc chloride is used to tune structure. A piezoresistive pressure sensor based on the wrinkled graphene foam is assembled. Benefiting from the unique contact interface of wrinkled microstructures, as well as the mechanical strength and the superior resilience of the foam structure, the piezoresistive pressure sensor exhibits a reliable stability (>105 cycles), short response time(150 ms)and low relaxation time (120 ms). And it also demonstrates good performances in various applications, such as pulse detection, voice recognition as well as the finger joints movement. It is suggested that the pressure sensor based on wrinkled graphene foam has great potential in flexible electronics to achieve health monitoring and motion detection. It also paves the way for other wrinkled materials to be involved in the fabrication of pressure sensors.

Fullerenes have been widely used as the electron transport layers (ETL) for planar-heterojunction perovskite solar cells (PSCs), due to their superior abilities in electron transporting, hysteresis suppression and low-temperature processing. Here, we demonstrate a novel inverted PSC with evaporated C60 as ETL and dopant-free copper phthalocyanine (CuPc) as hole transport layer (HTL). The C60 ETL can not only transport photogenerated electrons, but also passivate grain boundaries and surfaces of perovskite films effectively. By optimizing the thickness of the C60 ETL, a champion power conversion efficiency (PCE) of 16.72% is obtained with almost no hysteresis and less than 10% decay in efficiency is observed during a two-week stability test. To the best of our knowledge, this is the highest efficiency of the inverted PSCs employing CuPc as HTL. For comparison, the devices using PCBM as ETL are also prepared and only achieve a highest efficiency of 15.74%. Various characterizations and analyses attest the enhanced charge transport and extraction as well as suppressed charge recombination and hysteresis for the C60-based devices. Since all the processes are accomplished under a low temperature, this enable us to fabricate flexible PSCs on polyethylene terephthalate (PET) substrates with a highest PCE of 12.96%. Our work provides a new strategy for fabricating cost-effective, highly efficient and hysteresis-free flexible PSCs in mass production.

Electron transport layer (ETL), functioning as the electron transportation and extraction layer as well as hole-blocking layer, plays an important role in planar perovskite solar cells (PSCs). Majority of the state-of-the-art PSCs contain a TiO2 ETL always requiring a high temperature (500 °C) treatment, which is both energy-consuming and incompatible with flexible substrates, thus hindering large-scale application in flexible devices. Here, we demonstrated a low-temperature (70 °C) solution-processed Mg-doped rutile TiO2 as ETL in planar PSCs, while the thermal-evaporated copper phthalocyanine (CuPc) and doctor-bladed carbon were introduced as the hole transport layer (HTL) and counter electrode, respectively. The as-prepared PSC obtains a 15.73% power conversion efficiency (PCE), which is quite an excellent efficiency among carbon-based planar PSCs, getting an increase by 16% compared to the 13.56% PCE of the pristine TiO2-based device. The prominent increment is mainly attributed to the faster charge extraction, better electrical conductivity and suppressed charge recombination of Mg-doped TiO2. Besides, using highly stable CuPc and commercial carbon makes the as-prepared PSCs highly durable over 30 days when exposed to the ambient air with a relative humidity of 50%. Since all the processes are conducted under 100 °C, our work paves a way for developing cost-effective and highly stable PSCs compatible with flexible substrates.