Broad Spectral Response Research Articles

Air‐Stabilized Lead‐Free Hexagonal Cs3Bi2I9 Nanocrystals for Ultrahigh‐Performance Optical Detection

AbstractBroadband photodetectors possess enormous potentials for diverse applications while it is generally subjected to a lack of active materials with high performances under user‐friendly conditions. Bismuth‐based perovskites are promising and demonstrate better air stability than lead halide perovskites against moisture, heat, and light. In the present work, lead‐free all‐inorganic hexagonal Cs3Bi2I9 perovskite nanocrystals are successfully fabricated via a modulated colloidal synthetic route. The Cs3Bi2I9 nanocrystals are monodispersed with a size of ≈28 nm, which are applied for the construction of flexible Cs3Bi2I9 detector and vertical heterogeneous structured photodetector of p‐Si/Cs3Bi2I9/graphene. The flexible detector not only demonstrates excellent detective performance, but also yields high‐resolution photographs as an imaging sensor. The p‐Si/Cs3Bi2I9/graphene photodetector exhibits broad spectral response from ultraviolet to infrared light (254−1064 nm) with microsecond response time (31/34 µs). In particular, it performs with a high responsivity of 23.6 A W−1 and a high specific detectivity of 1.75 × 1013 Jones under 650 nm illumination even in weak light intensity as low as 1 µW cm−2, and exhibits excellent stability in ambient air, which is obviously ahead of the previously reported work. In addition, finite element analysis further demonstrates the excellent optoelectronic properties of Cs3Bi2I9 materials and the broad spectral response of vertical heterojunctions.

The improvement design of two-colour pyrometry for pulsed laser deposition system

In this work, we develop a digital pyrometry with an automatic control system. A two-colour pyrometer is applied to measure the substrate surface temperature in the pulsed laser dep-osition (PLD) system. A digital computer and two-colour photodetector are coupled to obtain the substrate surface temperature and the output signal from the respective detectors with high accuracy. These sets enable us to determine the substrate temperature during the process of deposition remotely and potentially allow us to develop control routines for maintaining a constant temperature throughout the process. The designed system has a broad spectral response range from 0.32 to 1.7μm and achieves a deficient full-scale temperature error of <1.8°C. Factors affecting the temperature measurements are studied to identify the sensor limitations, such as possible damage on the two-colour photodetectors, spectral losses, responsivity, and the distance between the photodetector end to the substrate. Finally, this pyrometric system is applied in the PLD process to maintain a stable substrate surface temperature.

Hybrid CsPbBr3 quantum dots decorated two dimensional MoO3 nanosheets photodetectors with enhanced performance

Molybdenum trioxide (MoO3) have gained considerable attention for their wide applications ranging from optoelectronics, solar cells to energy storage. Herein, we obtained high crystalline MoO3 nanosheets (NSs) through a vapor phase epitaxy (VPE) method. A photodetector (PDs) based on MoO3 NSs was fabricated on the SiO2/Si substrate and the PDs exhibit a striking photoresponse under ultraviolet (UV) light. Furthermore, by introducing a CsPbBr3 QDs the photocurrent of the MoO3 devices was enhanced by 2 orders of magnitude than the pristine counterpart. The enhanced photocurrent could be ascribed to the interfacial charge transfer from CsPbBr3 QDs to MoO3. The hybrid CsPbBr3 QDs/MoO3 photodetectors exhibit high responsivity with high on/off ratio under UV light illumination. Furthermore, the performance of the hybrid device, extending from UV to visible light, has ensured broad spectral response of the device. This work indicates that CsPbBr3 QDs/MoO3 hybrids can be promising for the construction of broad band photodetectors and other optoelectronic devices.

Neodymium metal nanorods as camptothecin-carriers

Metal nanoparticles possess a single element, thus minimizing the complexity and toxicity. It is fascinating to develop newer metal nanomaterials for such applications. We report, for the first time, a systematic synthesis and characterization of neodymium nanorods. Their broad spectral response extends from the UV–vis to the NIR-II wavelength range. The nanorods are paramagnetic. They are made as a nanocarrier by coating them with a poly-β-cyclodextrin polymer. The release of the loaded camptothecin on the nanocarrier takes place over a period of 300 h. The anticancer efficiency of the camptothecin-loaded on the nanocarrier is reported. Since the neodymium nanoparticles possess a high aspect ratio, absorb light in the NIR wavelength range, and possesses a photoluminescent property. They can emerge as a new nanomaterial of interest in the fields of anticancer drug delivery and photothermal therapy.

Broad Spectral Response Z-Scheme Three-Dimensional Ordered Macroporous Carbon Quantum Dots/TiO2/g-C3N4 Composite for Boosting Photocatalysis.

Photocatalytic degradation technology is one of the effective protocols to solve environmental problems. TiO2 has always been favored for its photostability and low cost. However, the insufficient photocatalytic activity of TiO2 limits its application due to the severe recombination of photogenerated electrons and holes and a narrow light response range. Therefore, 3DTCN, a TiO2/g-C3N4 composite with a three-dimensional ordered macroporous structure was prepared by a colloidal crystal template technique to form a heterojunction for inhibiting the photogenerated electron-hole recombination. On 3DTCN, carbon quantum dots (CQDs) were loaded by impregnation to obtain x % CQDs/3DTCN with a broad spectral response to light. The physical and chemical properties of samples were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution-TEM, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller analysis, photoluminescence spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activity was evaluated via degrading the rhodamine B (RhB) dye, and the degradation efficiency of 1% CQDs/3DTCN (98%) was found to be much higher than that of 3DTCN (42%) in 80 min under simulated sunlight irradiation. Furthermore, it also possessed excellent durability. Meanwhile, the sample also showed an outstanding photoelectric property. Finally, the proposed mechanism of the composites had been mainly analyzed by density functional theory calculations. This work thus provides an idea to form a 3D structure heterojunction and further improve the photocatalytic activity.

Harvesting the infrared part of solar light to promote charge transfer in Bi2S3/WO3 photoanode for enhanced photoelectrochemical water splitting

Infrared light absorbed by semiconductors hardly contributes to the solar energy conversion due to its low photon energy. Herein, photothermal effect activated by infrared part of solar light is introduced to promote the photoelectrochemical (PEC) water splitting of photoanodes. Narrow band-gap semiconductor Bi2S3 is deposited on the surface of WO3 nanosheets, exhibiting a broad-spectral response. In addition to the enhanced density of photo-generated electrons, significant temperature elevation is observed for the Bi2S3/WO3 composite photoanode under the illumination of infrared part of solar light because of the photothermal conversion property of Bi2S3. The moderately enhanced temperature accelerates charge carrier migration and finally increases the efficiency of solar energy conversion. With the assistance of photothermal effect, a remarkable photocurrent density of 4.05 mA cm−2 at 1.23 V vs. reversible reference electrode (VRHE) is achieved by Bi2S3/WO3 composite photoanode, over 880% higher than that of the pristine WO3. The introduction of photothermal effect activated by infrared light provides general and robust strategy to promote the PEC performance of photoanodes.

C–O band structure modified broad spectral response carbon nitride with enhanced electron density in photocatalytic peroxymonosulfate activation for bisphenol pollutants removal

Here, a simple one-step calcination method uses glycolic acid (GA) and urea to synthesize C-O band structure modified carbon nitride with broad spectral response, which is used to construct a peroxymonosulfate/visible light (PMS/vis) system. The solid-state 13C NMR proved that C-O band structure was successfully introduced into the carbon nitride. Density functional theory (DFT) calculation show that the introduction of C-O band structure shortens the band gap of 0.05 g GA modified CN (0.05 GA-CN). Besides, Ultraviolet photoelectron spectroscopy (UPS) further illustrate that the 0.05 GA-CN has a higher charge density and promotes the degradation of pollutants. In PMS/vis system, 0.05 GA-CN can completely degrade bisphenol A (BPA) within 36 min. In addition, 0.05 GA-CN can also degrade bisphenol E (BPE) and bisphenol F (BPF). The cyclic voltammetry (CV) curve show that the introduction of C-O band structure enhances the activation ability of PMS. At the same time, 0.05 GA-CN/PMS has enhanced the activity of degrading BPA under blue light (450–462 nm), green light (510–520 nm) and red light (610–625 nm). This research provides a new method to synthesize carbon nitride with enhanced electron density for degradation of bisphenol pollutants in PMS/vis system.

Model parameter identification for scaled-down analogous HVDC transmission lines using broad spectral response analysis

Traditional analogous π-shape transmission line models are mainly designed based on the amplitude and phase response characteristics of the distributed-parameter transmission lines at the power frequency. It cannot be directly used to build analogous high-voltage direct current (HVDC) transmission line models because the signals in a wide frequency band from 0 Hz to 10 kHz are used to protect HVDC transmission lines instead of power frequency components. In this paper, a novel model parameter identification method for scaled-down analogous HVDC transmission lines is proposed based on broad spectral response analysis. The broad spectral responses of distributed parameter-based and π-shape lumped parameter-based models are analyzed and compared with each other first. And then frequency-dependent per-unit parameters of HVDC transmission lines are obtained and used to form a modified π-shape HVDC transmission line model with the same zero- and positive-sequence​ impedance as those of distributed parameter lines. The element parameters of the π-shape circuit model are identified optimally based on the weighted sum of the results at selected several frequencies in the broadband from 0 hertz to thousands of hertz. The simulation results show that the amplitude and polarity of the dc voltage and current in our scaled-down analogous lines are close to distributed parameter-based HVDC transmission lines once a fault occurred on the lines.

Toward Broad Spectral Response Inverted Perovskite Solar Cells: Insulating Quantum‐Cutting Perovskite Nanophosphors and Multifunctional Ternary Organic Bulk‐Heterojunction

AbstractExtending near‐infrared (NIR) spectral response and increasing ultraviolet utilization is still a challenge in the context of improving power conversion efficiency (PCE) for perovskite solar cells (PSCs). In this work, to extend NIR light‐harvesting of PSCs, a novel COTIC‐4F: PC61BM: PTB7‐Th ternary organic bulk‐heterojunction together with Au nanotriangles is integrated on the PSCs. The NIR spectral response is thus extended to 1100 nm. In fact, the COTIC‐4F: PC61BM: PTB7‐Th layer enables multi‐functional effects, which can serve as electron transport, trap passivation, and moisture barrier layer in addition to NIR light harvesting. For increasing UV utilization, CsPbCl3:Yb3+, Ce3+, Cr3+ nanophosphors with photoluminescent quantum yield close to 200% are fabricated, which demonstrate excellent down‐conversion ability. Then, CsPbCl3: Yb3+, Ce3+, Cr3+/polymethylmethacrylate composite films are self‐assembled on a hybrid device, resulting in a 6.2% relative enhancement of short circuit current density. After simultaneously improving the NIR and UV spectral response of device, the PCE is increased significantly from 20.52% to 23.40% and the Jsc is increased from 21.79 to 25.96 mA cm−2, representing one of the highest PCE and maximum Jsc enhancements in the reported inverted hybrid organic/PSCs. This work represents an effective and general strategy for obtaining efficient and stable PSC devices with extremely broad spectral responses.

Self-powered high-performance flexible GaN/ZnO heterostructure UV photodetectors with piezo-phototronic effect enhanced photoresponse

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.

Applications of Lead‐Free Cs2AgBiBr6 Single Crystals in Photodetectors and Self‐Powered Photodetectors by Symmetric/Asymmetric Electrodes

AbstractLead halide hybrid perovskites have been intensively explored as light‐harvesting materials owing to their unique optoelectrical characteristics and simple deposition method. However, the toxicity and instability problems are still hindering their further development and applications. Herein, stable lead‐free double perovskite Cs2AgBiBr6 single crystals (SCs) with outstanding photoelectric properties are prepared. When symmetric Au electrodes are used, the resulting photodetectors (PDs) can have broad spectral response, high responsivity of 4.88 A W−1, external quantum efficiency of 1100%, and detectivity of 1.22 × 1013 Jones, respectively. More interestingly, when asymmetric electrodes (Au and Ag) are used, the authors obtain the first reported self‐driven PD based on the lead‐free perovskite SC, to the best of the authors’ knowledge. The device exhibits good photoresponse properties at a bias of 0 V. Both devices hold short response time at µs scale, which are among the best reported lead‐free perovskite PDs. Both devices demonstrate decent stabilities in air without encapsulation. All results demonstrate that Cs2AgBiBr6 SCs have great potential in the application of optoelectronic devices.

Ensemble GaAsSb/GaAs axial configured nanowire-based separate absorption, charge, and multiplication avalanche near-infrared photodetectors.

In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate absorption, charge, and multiplication (SACM) region-based nanowire avalanche photodetector device on non-patterned Si substrate is presented. Our device exhibits a low breakdown voltage (VBR) of ∼ −10 ± 2.5 V under dark, photocurrent gain (M) varying from 20 in linear mode to avalanche gain of 700 at VBR at a 1.064 μm wavelength. Positive temperature dependence of breakdown voltage ∼ 12.6 mV K−1 further affirms avalanche breakdown as the gain mechanism in our SACM NW APDs. Capacitance–voltage (C–V) and temperature-dependent noise characteristics also validated punch-through voltage ascertained from I–V measurements, and avalanche being the dominant gain mechanism in the APDs. The ensemble SACM NW APD device demonstrated a broad spectral room temperature response with a cut-off wavelength of ∼1.2 μm with a responsivity of ∼0.17–0.38 A W−1 at −3 V. This work offers a potential pathway toward realizing tunable nanowire-based avalanche photodetectors compatible with traditional Si technology.

Polarimetric Image Sensor and Fermi Level Shifting Induced Multichannel Transition Based on 2D PdPS (Adv. Mater. 2/2022)

Broad-Spectrum Photodetection In article number 2107206, Yue-Yang Liu, Zhongming Wei, and co-workers show how upward movement of the Fermi level enables multichannel transition of electrons. This mechanism achieves a broad spectral response in a PdPS-based photodetector. In addition, the PdPS-based polarization-sensitive photodetector and polarimetric image sensor realize the application of object detection.

A multilevel nonvolatile visible light photomemory based on charge transfer in conformal zinc–tin oxide/Au nanoparticle heterostructures

A photomemory based on a ZTO/Au NP heterostructure is revealed. It exhibits a broad spectral response and great retention to visible light due to the charge transfer at the ZTO/Au NP interface and surface plasmon resonance (SPR) of Au NPs.

Plasmon resonance in photoactive P-N junction blend, spin coated from self-made low cost spin coating machine for plastic solar cell

In the present work, spin coated thin films of P3HT: NTCDA donor- acceptor blends of weight ratios 3:1, 1:1 ,1:3 are prepared in Toluene using the self-made spin coating machine. The experiment is focused to optimize the P:N weight ratio of the photoactive blend that can absorb maximum solar energy and also to enhance the absorption by doping it with gold nano particles. Absorption property of the samples are studied using JASCO UV VIS 670 spectrometer which shows that 1:3 blend has the broad spectral response and considered to be the best active blend. The optical band gaps of the samples are determined through Tauc’s plot, wherein the onset wavelength for 1:3 sample is found to be 660nm with a band gap of 1.87 eV. The optimized 1:3 blend is doped with gold nano-particle dispersion in citrate buffer. The absorbance gets increased on doping with nano particle with extremely broadened spectral response which is attributed to the Localized Surface Plasmon Resonance(LSPR). Photons are trapped by the gold particles in the polymer matrix for the efficient harvesting of the solar energy. The construction of the solar cell using this Plasmon enhanced photoactive material is the work under progress. Copyright © 2017 VBRI Press.

Transparent graphene electrodes based hybrid perovskites photodetectors with broad spectral response from UV–visible to near-infrared

A new class of transparent graphene electrode based organic–inorganic halide perovskite photodetectors with broad spectral response is developed. These ultrasensitive devices exhibit high ON/OFF current ratio, high linear dynamic range, broad spectral range, excellent detection for weak light and easy fabrication with low-cost. Their semi-transparent feature and distinct photodetecting function for both sides would provide new applications affecting our daily lives.

Photocatalytic H2O2 production and removal of Cr (VI) via a novel Lu3NbO7: Yb, Ho/CQDs/AgInS2/In2S3 heterostructure with broad spectral response

The low-usage of solar energy and the sluggish separation efficiency of the photogenerated electrons/holes pairs are the obstacles in the practical application of photocatalysts. The integration of upconversion and Z-scheme heterojunction is expected to break the barriers to achieve the efficient charge separation and broaden near-infrared light absorption. Herein, an effective indirect Z scheme AgInS2/In2S3 heterostructure with carbon quantum dots (CQDs, as the electron conduction medium) and Lu3NbO7:Yb, Ho (as upconversion function) has been successfully synthesized. Consequently, the Lu3NbO7: Yb, Ho/CQDs/AgInS2/In2S3 heterostructure exhibited superior photocatalytic activities for Cr(VI) reduction and H2O2 production, reducing 99.9% of Cr(VI)(20 ppm, 15 min) and 78.5% of Cr(VI) (40 ppm, 30 min) with visible light irradiation as well as 94.0% of Cr(VI) (20 ppm, 39 min) under NIR light irradiation. Simultaneously, the heterostructure could generate 902.9 μM H2O2 for 5 h under visible light irradiation. The intensive photocatalytic properties could primarily be attributed to the boosted light absorption capacity, the improved solar-to-energy conversion by the remarkable upconversion capacity of Lu3NbO7: Yb, Ho/CQDs and the faster charge transfer through a Z-schematic pathway. This work is anticipated to open a novel “window” for designing the efficient photocatalysts by coupling of Lu3NbO7: Yb, Ho and CQDs.

Development of wavelength-resolved 3D-inegrated TL and OSL reader system

A new wavelength-resolved thermo luminescence (TL) cum optically stimulated luminescence (OSL) reader system has been designed and developed. This reader system uses the compact Seya-Namioka optical layout based monochromator, PMT, and resistive heating method to acquire TL glow curve emissions spectrum. The phosphor samples heated from room temperature to 400 °C, either linearly with a programmable heating rate of 0.01 to 30 K s−1 or alternative constant step temperature profiles. The TL glow curve emission spectrum has been resolved by rotating the grating attached to a monochromator covering the wavelength from 200 to 900 nm. The wavelength scanning is linear with respect to time and the scan rate can be selected from 0.1 to 8 n m s−1. A broad spectral response of the PMT detection module has been used to record the emitted TL spectrum. The blue (465 nm) reference LED light source is provided for a spectrum calibration of the monochromator. The isometric 3D TL emission spectra of LiCaAlF6:Eu,Y, α-Al2O3:C, and CaSO4:Dy have been successfully recorded using this reader system. In order to record the OSL emission spectrum, 470 nm blue LEDs have been provided as a separate stimulation module.

Flexible Photodetectors with High Responsivity and Broad Spectral Response Employing Ternary SnxCd1–xS Micronanostructures

Flexible Photodetectors with High Responsivity and Broad Spectral Response Employing Ternary Sn_<i>x</i>Cd_1–<i>x</i>S Micronanostructures

Graphene-based metasurface absorber for the active and broadband manipulation of terahertz radiation

Graphene-based metasurface nearly perfect absorbers (MPAs) can be used as an efficient tool for the active control and manipulation of waves in the terahertz (THz) gap. Here, we propose a novel, to the best of our knowledge, graphene-based MPA that is designed based on a simple configuration and is capable of absorbing THz radiation within a broad bandwidth of almost 3 THz with polarization-insensitive and omnidirectional characteristics. The MPA comprises a periodic array of graphene patches with two different dimensions that are separated from a gold bottom reflector with an S i O 2 spacer layer. The broadband spectral response of the MPA, which is also verified by analytical calculations, is due to the support of propagating surface plasmon excitations and can be either actively tuned via changes in the chemical potential of graphene or passively adjusted by the modification of the geometrical parameters of the patches and thickness of the spacer layer. As a complement to the previous studies in the literature, due to the simplicity of its design and broad spectral response, it is believed that the suggested graphene-based MPA will find potential applications in THz spectroscopy and communications.