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Self-powered and flexible perovskite photodetectors are holding great promise owing to their potential for high-performance wearable and portable optoelectronic applications. The light-induced ferro-pyro-phototronic effect can boost the performances of ferroelectric materials-based photodetector systems significantly. However, the utilization of the ferro-pyro-phototronic effect in polycrystalline halide perovskites films-based flexible photodetectors is rarely mentioned. Here, a ferro-pyro-phototronic effect boosted self-powered, flexible, and ultra-stable photodetector based on 1D/3D mixed perovskite ferroelectric film/P3HT heterojunction is demonstrated. By employing Pb(SCN) 2 as lead source to partially for fabricating high-quality MAPbI 3 film and incorporating 1D ferroelectric perovskite TMIMPbI 3 , the overall optoelectronic performances were largely enhanced, with a low dark current of 7 × 10−9 A, a responsivity of 6.6 mA/W and a detectivity of 5 × 109 Jones. The PDs displayed good folding endurance, and anti-humidity stability. The excellent performance is attributed to the reduced trap-density and enhanced pyro-phototronic effect induced by improved crystallinity and introduced ferroelectricity. [Display omitted] • A simple and effective method to prepare highly crystalized 1D/3D ferroelectric perovskite film was demonstrated. • The ferro-pyro-phototronic effect has been utilized to boost the photocurrent of self-powered flexible photodetector. • The PDs display favorable folding endurance and anti-humidity stability. [ABSTRACT FROM AUTHOR]

2D Ruddlesden-Popper (RP) perovskites have attracted enormous attention in optoelectronic fields compared with their 3D counterparts. However, most of the reported perovskite ferroelectrics-based self-powered photodetectors (PDs) are fabricated from bulk single crystals rather than perovskite thin films with improved reproducibility, flexibility, and less preparation time. Nevertheless, the defect sites at surfaces and grain boundaries of 2D perovskites polycrystalline films make them vulnerable to humidity. Herein, the highly crystallized 2D RP perovskite ferroelectric films are successfully obtained. Then, a passivation method is applied on 2D perovskite film by an in-situ reaction with 4-fluoro-phenylethylamine iodide (4-FPEAI), which reduces the defect sites and endows the perovskite films with the outstanding hydrophobic property. Then, the as-prepared 2D-perovskite ferroelectric thin films were fabricated into self-powered PDs. Boosted by the ferro-pyro-phototronic effect, the self-powered PDs demonstrate excellent optoelectronic performances at 360 nm, with dark current less than 1 × 10−12 A, a peak responsivity over 1 A W−1, a detectivity of 1.5 × 1014 Jones and fast response/recovery speed. The photoresponsivity and specific detectivity are both enhanced by 67.8 times regarding the relative peak-to-peak current, compared with those only based on the photovoltaic induced photocurrent. Further, the PDs show high stability towards high humidity and thermal treatment. Herein, the highly crystallized 2D RP perovskite ferroelectric films are successfully obtained. Then, a passivation method is applied on 2D perovskite film by an in-situ reaction with 4-fluoro-phenylethylamine iodide, which reduce the defect sites and endow the perovskite films with the outstanding hydrophobic property. Then, the as-prepared 2D-perovskite ferroelectric thin films were fabricated into self-powered photodetectors (PDs). Boosted by the ferro-pyro-phototronic effect, the self-powered PDs demonstrate excellent optoelectronic performances at 360 nm, with dark current less than 1 × 10−12 A, a peak responsivity over 1 A W−1, a detectivity of 1.5 × 1014 jones and fast response/recovery speed. The photoresponsivity and specific detectivity are both enhanced by 67.8 times regarding the relative peak-to-peak current, compared with those only based on the photovoltaic induced photocurrent. The PDs show high stability towards high humidity and thermal treatment. [Display omitted] • 2D RP perovskite ferroelectric films are demonstrated for ferro-pyro-phototronic effect based-self-powered UV photodetector. [ABSTRACT FROM AUTHOR]

A novel infrared light emitting diode (LED) based on an ordered p-n heterojunction built of a p-SiGe alloy and n-ZnO nanowires has been developed. The electroluminescence (EL) emission of this LED is in the infrared range, which is dominated by the band gap of SiGe alloy. The EL wavelength variation of the LED shows a red shift, which increases with increasing mole fraction of Ge. With Ge mole fractions of 0.18, 0.23 and 0.29, the average EL wavelengths are around 1,144, 1,162 and 1,185 nm, respectively. The observed magnitudes of the red shifts are consistent with theoretical calculations. Therefore, by modulating the mole fraction of Ge in the SiGe alloy, we can adjust the band gap of the SiGe film and tune the emission wavelength of the fabricated LED. Such an IR LED device may have great potential applications in optical communication, environmental monitoring and biological and medical analyses. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A self-powered, piezotronic effect-enhanced glucose sensor based on metal-semiconductor-metal (M-S-M) structured single ZnO nanowire device is demonstrated. A triboelectrical nanogenerator (TENG) is integrated to build a self-powered glucose monitoring system (GMS) to realize the continuously monitoring of glucose concentrations. The performance of the glucose sensor is generally enhanced by the piezotronic effect when applying a -0.79% compressive strain on the device, and magnitude of the output signal is increased by more than 200%; the sensing resolution and sensitivity of sensors are improved by more than 200% and 300%, respectively. A theoretical model using energy band diagram is proposed to explain the observed results. This work demonstrates a promising approach to raise the sensitivity, improve the sensing resolution, and generally enhance the performance of glucose sensors, also providing a possible way to build up a self-powered GMS. [ABSTRACT FROM AUTHOR]

The quest and development of optoelectronic sensors with high performance, sustainable, wearable, portable, and maintenance-free operation offers a significant impetus to explore self-powered flexible photodetectors (PDs). Here, a p-GaN/n-ZnO heterostructure-based self-powered and flexible ultraviolet PD is demonstrated by combining laser lift-off of GaN film and hydrothermal synthesis of ZnO nanowires. The device shows a large on/off current ratio (up to 7.36 ×106), outstanding detection sensitivity (6.82 ×1013 Jones), and fast response (6.9/6.4 ms) at 325 nm illumination at a bias voltage of 0 V, also exhibiting a relatively broad spectral response, remarkable reproducibility under thousands of switching cycles, and superior mechanical stability. In addition, since both GaN and ZnO are piezoelectric semiconductor materials, the piezoelectric charges created at two sides of heterojunction interface under an external strain will regulate the separation, extraction and recombination of photo-generated carriers based on the piezo-phototronic effect, resulting in an enhancement of relative responsivity up to 22% with a compressive strain of − 0.48% under UV illumination of 38.4 mW/cm2. This work not only exhibits a self-powered flexible optoelectronic device with potential applications in photo-sensing for artificial skin, optical communication, and self-powered integrated systems, but also provides a strategy to optimize the performance of prospective optoelectronic sensors via the piezo-phototronic effect. A self-powered high-performance flexible ultraviolet photodetector was fabricated based on p-GaN/n-ZnO heterostructure, which shows extraordinary on/off current ratio, detectivity, sensitivity and stability at a bias voltage of 0 V. Additionally, owing to the piezoelectricity in both GaN and ZnO, the device photoresponse can be enhanced by piezo-phototronic effect under applied external strain. [Display omitted] • A p-GaN/n-ZnO heterostructure-based UV PD exhibiting flexible and self-powered simultaneously is fabricated. • The flexible self-powered PD shows a large on/off current ratio, superior detectivity, fast response, and good stability. • An enhancement on photoresponse of the PD is realized based on the piezo-phototronic effect. [ABSTRACT FROM AUTHOR]

• A TENG-based self-powered high temperature alarm sensor system has been demonstrated. • High temperature resistant PI nanofiber film has been used as the friction material. • This self-powered sensor is based on thermal snap-through of bimetallic strip. [Display omitted] The failure of mechanical or electronic equipment caused by high temperature brings huge economic losses. At the same time, the potential fire danger brought by high temperature threatens people's lives. Realizing high temperature alarm is a double test of the material preparation and device construction. Here, a novel self-powered high temperature alarm sensor has been realized based on the combination of triboelectric nanogenerator and bimetallic strip. Besides, electrospun polyimide (PI) nanofiber membranes were prepared as the high temperature resistant friction material. When encountering high temperature, the rapid deformation of bimetallic strip can make it interact with the PI friction material to generate electrical signals for alarm. Finally, a series of demonstrations showed the wide application potential of the system in high temperature alarm. [ABSTRACT FROM AUTHOR]

• Pyro-phototronic effect enhanced by LSPR is utilized to design a self-powered UV photodetector. • Responsivity and detectivity attain 0.485 mA/W and 27.49 × 1010 Jones for UV light with the power density of 68 nW/cm2. • The responsivity and detectivity show significant enhancement by decorating Au NPs on the surface of ZnO NWs. • The present study offers a practical approach to improve the performance of photodetector with other nanomaterial systems. [Display omitted] Ultralow power density UV sensing is crucial to application in military and civilian fields. However, it is still confronted with a low signal-to-noise ratio and long response/recovery time. Here, we report a self-powered photodetector based on the Schottky junction of Au NPs@ZnO NWs, which can detect 325 nm light with the power density of 68 nW/cm2, by using pyro-phototronic effect enhanced by localized surface plasmon resonance (LSPR). Under the illumination of 325 nm with the power density of 68 nW/cm2, responsivity of photodetector dramatically enhances from 0 to 0.485 mA/W after decorating Au NPs, detectivity is boosted from 0 to 27.49 × 1010 Jones. The responsivity and detectivity of self-powered photodetector show significant enhancement of over 3290% and over 3298% under the illumination of 325 nm light with the power density of 170 nW/cm2. The fast recovery ensure detection can be finished within 12 ms. The coupled effect of pyroelectric effect and LSPR provides a guideline to design a high-performance photodetector using other nanomaterials. [ABSTRACT FROM AUTHOR]

GaN ultraviolet (UV) photodetectors (PDs) have attracted tremendous attention due to their chemical stability in harsh environments. Although Schottky-contacted GaN-based UV PDs have been implemented with better performance than that of ohmic contacts, it remains unknown how the barrier height at local Schottky contacts controls the sensors' performance. In this work, the piezotronic effect was employed to tune the Schottky barrier height (SBH) at local contacts and hence enhance the performances of Schottky-contacted metal-semiconductor-metal (MSM) structured GaN nanobelt (NB)-based PDs. In general, the response level of the PDs was obviously enhanced by the piezotronic effect when applying a strain on devices. The responsivity of the PD was increased by 18%, and the sensitivity was enhanced by from 22% to 31%, when illuminated by a 325 nm laser with light intensity ranging from 12 to 2 W/cm. Carefully studying the mechanism using band structure diagrams reveals that the observed enhancement of the PD performance resulted from the change in SBH caused by external strain as well as light intensity. Using piezotronic effects thus provides a practical way to enhance the performance of PDs made not only of GaN, but also other wurtzite and zinc blende family materials. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Nanowire solar cells are promising candidates for poweringnanosystemsand flexible electronics. The strain in the nanowires, introducedduring growth, device fabrication and/or application, is an importantissue for piezoelectric semiconductor (like CdS, ZnO, and CdTe) basedphotovoltaic. In this work, we demonstrate the first largely enhancedperformance of n-CdS/p-Cu2S coaxial nanowire photovoltaic(PV) devices using the piezo-phototronics effect when the PV deviceis subjected to an external strain. Piezo-phototronics effect couldcontrol the electron–hole pair generation, transport, separation,and/or recombination, thus enhanced the performance of the PV devicesby as high as 70%. This effect offers a new concept for improvingsolar energy conversation efficiency by designing the orientationof the nanowires and the strain to be purposely introduced in thepackaging of the solar cells. This study shed light on the enhancedflexible solar cells for applications in self-powered technology,environmental monitoring, and even defensive technology. [ABSTRACT FROM AUTHOR]

Abstract: Our living environment has an abundance of energies in the forms of light, thermal, mechanical (such as vibration, sonic wave, wind, and hydraulic), magnetic, chemical, and biological. Harvesting these types of energies is of critical importance for long-term energy needs and sustainable development of the world. Over the years, rationally designed materials and technologies have been developed for converting solar and mechanical energies into electricity. Photovoltaic relies on approaches such as inorganic pn junctions, organic thin films, and organic–inorganic heterojunctions. Mechanical energy generators have been designed based on principles of electromagnetic induction and piezoelectric effect. Innovative approaches have to be developed for conjunctional harvesting of multiple types of energies using an integrated structure/material so that the energy resources can be effectively and complimentarily utilized whenever and wherever one or all of them are available. We give a review on the hybrid cells that are designed for simultaneously harvesting solar and mechanical, and chemical and mechanical energies using nanotechnology. The two energy harvesting approaches can work simultaneously or individually, and they can be integrated in parallel and series for raising the output current and voltage, respectively. Innovative approaches have been demonstrated for developing integrated technologies for effectively scavenging available energies in our environment around the clock. [Copyright &y& Elsevier]

The likely goal of nanotechnology is the integration of individual nanodevices into a nanosystem, which includes the nanodevice(s), power harvesting unit, data processing logic system, and possibly wireless communication unit. A nanosystem requires a nanoscale power source to make the entire package extremely small and high performance. The nanofuel and nanobiofuel cells developed here represent a new self-powering approach in nanotechnology, and their power output is high enough to drive nanodevices for performing self-powered sensing. This study shows the feasibility of building self-powered nanosystems for biological sciences, environmental monitoring, defense technology and even personal electronics. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Pb-doped ZnO nanowires (NWs) have been synthesized by modified thermal evaporation method. Effect of Pb-doping on the morphology, structure, and optical properties of as deposited NWs have been investigated. The TEM images show that the doped NWs consist of cantilever-like with diameter in the range of 20–150nm. It has been found that the doped NWs are single crystalline grown along [101] direction. The composition and valence state of Pb ions have been investigated through energy dispersive spectroscopy (EDS) and X-ray photospectroscopy (XPS), which demonstrate that the Pb ions are uniformly doped into each NW and are in +2 oxidation state. In addition, photoluminescence spectra exhibit an increased amount of defects with increasing Pb, which leads to a red shift in the UV region. Furthermore, the band gap tailoring in Pb-doped ZnO NWs makes their potential for optoelectronics devices. [Copyright &y& Elsevier]

Abstract: The effect of high-energy (200keV) electron irradiation on ZnO-tetrapod (ZnO-T) nanostructure has been investigated by employing in situ scanning tunneling microscopy (STM) holder inside TEM. The microscopic results have revealed that the product consists of highly single-crystalline ZnO-T structures. The photoluminescence spectra show the increased amount of defects which lead to shift in the emission peak position in ultraviolet (UV) region and enhance the PL performance in visible luminescence (VL) region of ZnO-T nanocrystals. The in situ measurements show asymmetric Schottky contacts at the both ends interfaces under electron irradiation. The current–voltage (I–V) characteristics have revealed that the increase in electron density (range of ∼0–25pAcm−2) leads to an increase in the current along with the increase in carrier concentration from 1.1×1017 cm−3 to 3.2×1017 cm−3. In addition, it has been interestingly found that at high bias voltage, Schottky contacts turn to Ohmic contacts at the both ends with the influence of irradiation–matter interaction. The results strongly suggest that the ZnO-T is considered as a promising candidate for applications in irradiation environments. [Copyright &y& Elsevier]

Abstract: Bulk tip-shape ZnO nanowires (TSZONWs) have been synthesized via thermal evaporation method. The carbon nanotubes have been found to play an important role for the synthesis of this structure. The sensing capabilities of the structures have been investigated through electrochemical measurements. The photoluminescence spectra exhibit strong visible emission band due to an increase amount of defects, which leads to a significant role in the sensing applications. The electrochemical measurements prove that the TSZONWs are very sensitive to the pH of the PB solution as well as the bio-chemical species. Our investigation demonstrates that the arrays of TSZONWs can be employed for various applications. [Copyright &y& Elsevier]

Smart and wearable electromagnetic (EM) functional materials that can reasonably use EM energy and prevent EM pollution are of great significance to the future information society, but their design and preparation are still challenging. Here, a multifunctional EM response film is prepared based on a magnetic liquid metal droplet-filled elastomer with magnetic field-induced anisotropic structure, which can reversibly construct conductive network and tune heterogeneous interface during cyclic stretching. This film can withstand up to 600% tensile strain and shows stretching-enhanced electrical conductivity. Its EM interference shielding effectiveness (SE) significantly increases with stretching, and the relative SE change (ΔSE/SE 0) shows a linear response to the tensile strain. The specific shielding effectiveness (an ultrahigh value of 404 dB mm−1 at 400% strain) and strain sensitivity of the film outperform other stretchable EM functional materials. More interestingly, this film exhibits rapid switching between EM wave transmission and shielding through continuous stretching, which enables an off/on switchable EM interference shielding function. Furthermore, it can be used in a wearable EM sensor to wirelessly monitor human movements by recording changes of EM wave intensity. [Display omitted] • Magnetic liquid metal elastomer has magnetic field-induced anisotropic structure. • Conductive network and heterogeneous interface can be reversibly tuned. • Film has high flexibility, stretchability, stretching-enhanced conductivity. • Film exhibits an off/on switchable electromagnetic interference shielding. • Film is used in wearable electromagnetic sensor to wirelessly monitor human movement. [ABSTRACT FROM AUTHOR]

• Curved image sensor arrays possess the advantage of the wide field of view, low aberration, simple lens requirement. • The fabrication strategies for curved image sensor arrays are summarized. • The recent advance in curved image sensor array and its application in the artificial electronic eyes are focused. [Display omitted] A conventional wide-angle camera consists of a planar image sensor array and multiple optic elements, which increases the camera's volume, weight, and cost. In nature, most biological visual systems possess a curved retina, providing the capability of a wide field of view imaging with high sensitivity through a single lens. Inspired by the unique advantage of the biological eye, various curved image sensor arrays have been demonstrated, which enable a wide field of view, low aberration, and highly sensitive image acquisition with a simple lens design. Herein, various fabrication strategies for the curved image sensor arrays are summarized. In addition, the applications of the curved device in the artificial electronic eyes as well as the challenges and opportunities of the curved image sensor array are also discussed. [ABSTRACT FROM AUTHOR]

This paper reports the bulk synthesis route of the aligned and non-aligned high-quality α-Si3N4 nanowires (NWS) which were grown directly from the Si substrate by vapor phase deposition at 1050°. The as-grown products were characterized by employing XRD, SEM, HRTEM and photoluminescence. The microscopic results revealed that the products consist of single crystalline aligned and non-aligned α-Si3N4 NWs having a same diameter range of 30–100 nm and different lengths of about hundreds of microns. The XRD observation revealed that the products consist of α-phase Si3N4 NWs. The room temperature PL spectra indicated that the NWs have good emission property. The non-aligned NWs were formed at lower temperature as compared with aligned NWs. Our method is a simple and one-step procedure to synthesize the bulk-quantity and high-purity aligned and non-aligned α-Si3N4 NWs at a relatively low temperature. The possible growth mechanism was also briefly discussed. [ABSTRACT FROM AUTHOR]

Monitoring cardiovascular activities plays a critical role in predicting and preventing cardiovascular diseases. Flexible and biosafe sensors that can provide complementary information about cardiovascular activity beyond the traditional electrocardiogram (ECG) are in great demand. Here, a novel eco-friendly in-situ gap-generation method by vaporizing soaked distilled water is developed to fabricate a no-spacer triboelectric nanogenerator (NSTENG). This NSTENG reveals more uniform stress/strain distributions and undergoes larger displacement compared with the traditional TENG with spacer under the same pressure; and it obliterates the obstruction on detection of subtle movements near spacer. The unique fabrication method also guarantees biological safety and avoids air contamination in vivo. The established wireless mobile system based on the NSTENG can precisely detect the full pulse waveforms and display them on the phone screen in real time. By mounting onto the rat's heart, it can monitor normal heart motion and the measured heart rate has an accuracy of up to 99.73%. Moreover, the NSTENG can monitor abnormal heart motion and detect subtle heart movements that fail to be captured by the ECG. This work provides a new strategy that promotes the innovation of biosafe and new-structure TENGs, and offers new insights into developing wearable and implantable sensors. [Display omitted] • A novel eco-friendly in-situ gap-generation method is developed to fabricate no-spacer triboelectric nanogenerators (NSTENGs). • The method is carried out by vaporizing soaked distilled water, which guarantees biosafety and avoids unwanted air contamination in vivo. • The NSTENG reveals more uniform stress/strain distributions and undergoes larger displacement than TENG with spacer under the same pressure. [ABSTRACT FROM AUTHOR]

Anodic aluminum oxide (AAO) membranes with large ordered pore domains were successfully prepared by adopting the anneal pre-treatment of polycrystalline aluminum sheets. A statistical method with Gaussian distribution was introduced to quantitatively study the size of the domain with ordered pores. The largest average area of ordered pore domains was 2.6 μm2±0.11 μm2. The corresponding AAO membrane was synthesized by aluminum sheets annealed at 893 K for 24 h. [ABSTRACT FROM AUTHOR]