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III–V colloidal quantum dots (QDs) promise Pb and Hg-free QD compositions with which to build short-wavelength infrared (SWIR) optoelectronic devices. However, their synthesis is limited by the availability of group-V precursors with controllable reactivities to prepare monodisperse, SWIR-absorbing III–V QDs. Here, we report a one-pot heat-up method to synthesize ∼8 nm edge length (∼6.5 nm in height) tetrahedral, SWIR-absorbing InAs QDs by increasing the [In3+]:[As3+] ratio introduced using commercially available InCl3 and AsCl3 precursors and by decreasing the concentration and optimizing the volume of the reducing reagent superhydride to control the concentration of In(0) and As(0) intermediates through QD nucleation and growth. InAs QDs are treated with NOBF4, and their deposited films are exchanged with Na2S to yield n-type InAs QD films. We realize the only colloidal InAs QD photoconductors with responsivity at the technologically important wavelength of 1.55 μm. [ABSTRACT FROM AUTHOR]

This study aims to contribute to the development of theoretical and experimental tools for characterizing the transport properties of perovskite semiconductors. In the context of existing transport characterization methods for perovskites, there is a need for techniques that can accurately assess the critical transport parameters, such as diffusion lengths, given the specific challenges posed, such as their inherent instabilities. The novel methodology employed involves the development of a theoretical model to describe the running fringes-induced photo-electromotive force (RF photo-EMF) effect in bipolar photoconductors with a rather general type of photoconductivity relaxation behaviors for both carriers. This model is founded on the theory of photoinduced space charge grating formation in semiconductors. Subsequently, RF photo-EMF experiments were conducted on methylammonium lead iodide (CH 3 NH 3 PbI 3 or MAPI) polycrystalline films of varying grain sizes. By utilizing the RF photo-EMF technique, we successfully elucidated crucial transport and recombination characteristics, notably the ambipolar diffusion length and relaxation times of the charge carriers. Significantly, the developed theoretical model exhibited a remarkable agreement with the experimental results, highlighting its ability in explaining and predicting the behavior of charge carriers in perovskite semiconductors. The results of this study make a substantial contribution to the field of perovskite semiconductors by offering a novel theoretical and experimental approach to characterization of perovskites' transport properties. [ABSTRACT FROM AUTHOR]

Circularly polarized light (CPL) has attracted great attention due to its unique electromagnetic vector, which possesses potential practical applications in optical imaging, biometrics, and other interdisciplinary areas. At present, many materials with spontaneous CPL emitting have been extensively studied and reviewed for the generation of CPL. For the detection of CPL, mainly concentrate on the technical problems, that is, how to combine circularly polarized optical active materials with device structures to meet detection needs. Essentially, the resolution of CPL depends on the interaction between CPL and matter, Herein, the interactive modes including polarized light‐spin and light‐dipole (or charge) interactions in devices are summarized. Also, direct and indirect interactions of polarized light‐spin are presented. Meanwhile, the progress of light‐spin/dipole interaction dependence of CPL detectors is analyzed based on artificial structures of photoconductors, photodiodes, and photo field effect transistors. It is hoped that the review can broaden the bridge between the fundamental photon‐spin‐dipole interaction and CPL detectors with high performance, and then deepen the understanding of CPL detection and promote the development of CPL detectors. [ABSTRACT FROM AUTHOR]

Bulk black phosphorous (bP) exhibits excellent infrared (IR) optoelectronic properties, but most reported bP IR photodetectors are fabricated from single exfoliated flakes with lateral sizes of < 100 µm. Here, scalable thin films of bP suitable for IR photodetector arrays are realized through a tailored solution‐deposition method. The properties of the bP film and their protective capping layers are optimized to fabricate bP IR photoconductors exhibiting specific detectivities up to 4.0 × 108 cm Hz1/2 W−1 with fast 30/60 µs rise/fall times under λ = 2.2 µm illumination. The scalability of the bP thin film fabrication is demonstrated by fabricating a linear array of 25 bP photodetectors and obtaining 25 × 25 pixel IR images at ≈203 ppi with good spatial fidelity. This research demonstrates a commercially viable method of fabricating scalable bP thin films for optoelectronic devices including room temperature‐operable IR photodetector arrays. [ABSTRACT FROM AUTHOR]

Photoconductors featuring an individual micro/nano‐crystal as the photoactive channel hold the great promise for next‐generation integrated optoelectronics. Meanwhile, the gain aiming for signal amplification without an extra amplifier, the fast response for fast data transfer, and low dark current for weak signal acquisition are highly desirable in integrated optoelectronics, but are inherent trade‐off in traditional photoconductors. Herein, the study demonstrates a single‐microplate MAPbI3 photoconductor based on polyvinyl alcohol‐filled planar electrodes that can simultaneously achieve excellent performance on these parameters. The superior performance can be attributed to the exquisite design of filling the device channel gap with polyvinyl alcohol. This deep‐work‐function transparent polyvinyl alcohol can not only passivate surface defects of the perovskite microplate by hydrogen bonding, but also form a heterojunction with top perovskites to induce a depleted channel. Resultant single‐microplate photodetectors exhibit exceptional performance characteristics including ultra‐low noise‐equivalent power of 0.19 fW Hz−1/2, high specific detectivity of 3.68 × 1014 Jones, fast response of 3.2 µs, high EQE‐bandwidth over 107 Hz, as well as excellent stability. More importantly, single‐microplate MAPbI3 photoconductors demonstrate ultra‐weak‐light imaging ability surpassing silicon counterparts. Furthermore, the successful integration of their microplate pixels showcases the promising prospect for integrated optoelectronics. [ABSTRACT FROM AUTHOR]

HgCdTe is a well-known material for state-of-the-art infrared photodetectors. The interd-iffused multilayer process (IMP) is used for Metal–Organic Chemical Vapor Deposition (MOCVD) of HgCdTe heterostructures, enabling precise control of composition. In this method, alternating HgTe and CdTe layers are deposited, and they homogenize during growth due to interdiffusion, resulting in a near-uniform material. However, the relatively low (350 °C) IMP MOCVD growth temperature may result in significant residual compositional inhomogeneities. In this work, we have investigated the residual inhomogeneities in the IMP-grown HgCdTe layers and their influence on material properties. Significant IMP growth-related oscillations of composition have been revealed in as-grown epilayers with the use of a high-resolution Secondary Ion Mass Spectroscopy (SIMS). The oscillations can be minimized with post-growth annealing of the layers at a temperature exceeding that of growth. The electric and photoelectric characterizations showed a significant reduction in the background doping and an increase in the recombination time, which resulted in dramatic improvement of the spectral responsivity of photoconductors. [ABSTRACT FROM AUTHOR]

Highlights: Self-powered direct X-ray detectors, based on FAPbBr3 255-nm-thick films deposited onto mesoporous TiO2 scaffolds, can withstand a 26-day uninterrupted X-ray exposure with negligible signal loss, demonstrating ultra-high operational stability. Bulk specific sensitivity is evaluated to be 7.28 C Gy−1 cm−3 at 0 V, an unprecedented value in the field of thin-film-based photoconductors and photodiodes for "hard" X-rays. Sensitivity of submicrometer-thick perovskite films to the X-rays produced by a medical linear accelerator used for cancer treatment is here demonstrated for the first time. Metal-halide perovskites are revolutionizing the world of X-ray detectors, due to the development of sensitive, fast, and cost-effective devices. Self-powered operation, ensuring portability and low power consumption, has also been recently demonstrated in both bulk materials and thin films. However, the signal stability and repeatability under continuous X-ray exposure has only been tested up to a few hours, often reporting degradation of the detection performance. Here it is shown that self-powered direct X-ray detectors, fabricated starting from a FAPbBr3 submicrometer-thick film deposition onto a mesoporous TiO2 scaffold, can withstand a 26-day uninterrupted X-ray exposure with negligible signal loss, demonstrating ultra-high operational stability and excellent repeatability. No structural modification is observed after irradiation with a total ionizing dose of almost 200 Gy, revealing an unexpectedly high radiation hardness for a metal-halide perovskite thin film. In addition, trap-assisted photoconductive gain enabled the device to achieve a record bulk sensitivity of 7.28 C Gy−1 cm−3 at 0 V, an unprecedented value in the field of thin-film-based photoconductors and photodiodes for "hard" X-rays. Finally, prototypal validation under the X-ray beam produced by a medical linear accelerator for cancer treatment is also introduced. [ABSTRACT FROM AUTHOR]

Polycrystalline infrared lead salt detectors exhibit exceptionally high sensitivity near room temperature and, as such, are ubiquitous in commercial instruments such as spectrometers and flame detectors. The underlying physical mechanism behind this remarkable performance has been the subject of speculation for many years. In this treatise, data from work performed at BAE Systems and St. John's Optical Systems and from the published literature are analyzed to identify common mechanisms that contribute to the photoconductivity of polycrystalline lead salt detectors from a multitude of material deposition and process technologies, and it was concluded that much of the behavior can be attributed to surface-related phenomenon. Physical models are proposed to explain the observations. Finally, there is a brief description of measurements related to noise in these complex structures, indicating the importance of ohmic contacts, but the observed low frequency spectral noise density remains a mystery. [ABSTRACT FROM AUTHOR]

Herein, a simple, solvent‐free method to fabricate polymer‐encapsulated halide perovskite photoconductors is described. Dry mechanochemical synthesis is used to prepare CsPbBr3 in the presence of poly(butyl methacrylate) (PBMA). The resulting composite powder is then heated and pressed into a free‐standing disk with a thickness controlled by a metallic spacer ring. The disk can be laminated on a glass substrate patterned with interdigitated electrodes, resulting in a planar photoconductor device. The best photoconductive performance is obtained for disks that consist of 75 wt.% CsPbBr3 in PBMA, reaching a detectivity of ≈2 × 1011 Jones. Moreover, by adjusting the thickness of the disk, narrowband detectors can be obtained due to charge collection narrowing. Depending on the thickness of the pressed disk, the position and width of the detectivity peak can be tuned. At last, the disks are tested as possible absorber materials for X‐ray detectors, where ow detection limit, and fast and linear response are measured for perovskite‐polymer disks with 50 wt.% perovskite content. This work shows a simple and versatile approach toward the fabrication of halide perovskite photodetectors, which can be carried out in air and without the use of solvents. [ABSTRACT FROM AUTHOR]

In this article, we proposed an integrated application of automatic moisture and Irrigation control using Real-Time Clock (RTC) and Light-Dependent Resistor (LDR). The main idea of this paper is predicated on using as little energy as possible. In this work, we use the DS1307 real-time clock module to automatically switch on or off motor dependent on the time of day. The sensors are used for monitoring the soil conditions in agriculture field. Programming controls the timing of when the device is active. The most significant benefit of the proposed design is the reduction of risk associated with potential crashes and save water. Motors on the farm are often switched on at dry time and left OFF on wet conditions till necessity. Their operation is entirely automatic. Because of the protection of the farmers from the electrical shock during the rainy season, this proposed design intends to automate the operation of soil monitoring and irrigation in order to reduce water, power consumption and advance technological progress in agriculture farms and support in smart India. A significant amount of electricity is lost in the typical lighting system; however, this may be prevented with automatic control employing LDR. [ABSTRACT FROM AUTHOR]

The aim of the present study is to create the guided inquiry laboratory works in studying the photoelectric properties of semiconductors in order to foster the students’ research experiences. In this context, the general structure of guided inquiry laboratory work is proposed and described. Each laboratory work includes preparation section, experiment section, interpretation section and consolidation section. Two created laboratory works include five experimental investigations in luminous and current-voltage characteristics of CdS photoresistors, selenium and silicon solar cells. The use of self-made equipment allows students to be introduced to the general principles of creating installation for these experimental investigations. The advantages and possibilities of self-made device for studying the photoelectric properties of semiconductors have been formulated. The design of the device allows changing the illumination of the photodetectors, measure dark currents, determining the photocurrent, calculate the sensitivity of photodetectors, confirm sublinear law for photoresistors, and study the current-voltage characteristics for different luminous flux. The cost of manufacturing the device is quite low. The questions to consolidate knowledge are offered for each laboratory work. Described general method of performing guided inquiry laboratory work could be used in the study of other topics of physics. Proposed level of inquiry-based learning is successfully used by the authors of the present article during professional training of Bachelor’s and Master’s students, future physics teachers.

We consider the charge collection efficiency (CCE) for semiconductors in which the charge transport parameters, the drift mobility μ, and the carrier lifetime τ have spatial dependence, i.e., μ = μ(x) and τ = τ(x), where x is the distance from the radiation receiving top electrode toward the rear electrode. The small signal carrier packet drift analysis (CPDA) is re-examined, and the CCE efficiency for electrons and holes is formulated in terms of μ(x)τ(x)F(x), where F is the field. We use two model mobility and lifetime variations that are linear and exponential and then calculate and compare CCE determined from the CPDA equation, numerical solution of the continuity equation and Monte Carlo simulations as a function of the parameters characterizing the linear and exponential changes. The use of standard CCE equations for nonuniform samples is extensively examined, and errors are quantified by introducing a spatial average (SA) ⟨τ(x)⟩, average inverse (AI) ⟨1/τ(x)⟩, a new effective lifetime, and a kth order average. The SA lifetime works best when τ(x) monotonically decreases with x and AI works best when τ(x) monotonically increases with x. Stabilized a-Se x-ray photoconductors were considered as a practical application of this work. Both hole and electron lifetimes decrease in a-Se upon x-ray irradiation. Using the empirical equations derived recently for τh(x) and τe(x) as a function of dose D(x) in the sample, the CCE for two a-Se samples corresponding to a low-end device quality and the "best" was determined as a function of applied field. [ABSTRACT FROM AUTHOR]

Several experimental groups have reported recently an intriguing high level of gain (Photomultiplication) in vertical organic photoresistance (as well as in other technologies, such as perovskite for instance). This mechanism is sometimes named as "Trap-Assisted Photomultiplication." This paper investigates the origin of this mechanism by means of drift diffusion simulations, analytical theory, and experiments, considering the particular case of PCDTBT:PC60BM photoresistors, although some conclusions are likely to apply in other technologies. It turns out that an excess of charges (induced by electron–hole carrier generation) may trigger additional carrier injection, leading to photomultiplication, under specific circumstances. We call this mechanism "gain by injection enhancement." Electron (respectively, hole) trapping for P only (respectively, N only) devices can play this role efficiently. As these additional carriers came from contacts, significant dark current injection is thus needed to achieve a large value of gain, explaining why this mechanism can occur only in P (or N) only photoresistors (and not photodiodes or intrinsic photoresistors, i.e., with midgap contacts). In such devices, however, the detectivity remains intrinsically limited by the high level of dark injection currents required to get gain, and consequently, this type of device may be interesting, in particular, in technologies where it is not possible to achieve low dark currents using photodiodes. However, penalized by the slow trap dynamics, the cut-off frequency of these devices remains extremely low (<100 Hz). Also, this gain takes a high value only at low irradiance, making photoresistor responsivity light dependent. All these results bring new light in analyzing and optimizing photoresistors, opening a large field of investigation to take advantage of gain by injection enhancement. [ABSTRACT FROM AUTHOR]

Due to its atomically ultrathin morphology and superior optoelectronic properties, graphene has been broadly studied and utilized in phototransistors, photoconductors, or heterojunction nanostructures. However, in practical devices, the disadvantages of graphene should be concerned for its high dark current, very low on/off ratio, and high-priced fabrication cost. We report the photodetecting of the graphene/insulator/silicon heterojunction. The insulator layer is optimized to achieve balanced optoelectronic properties in terms of an Iph/Idark ratio of 4.17 × 103, a responsivity of 35 mA W−1, and a detectivity of 6.39 × 1010 Jones at a wavelength of 658 nm, with low operating voltage and static power dissipation (0.84 nW). Besides, response speed and degradation in the environment are tested. The mechanisms are revealed and analyzed by I-V measurements. [ABSTRACT FROM AUTHOR]

Neuromorphic hardware based on artificial synaptic devices has great potential to break the bottleneck of von Neumann architecture, which makes it possible to emulate the working mode of the human brain with low power consumption and high operation efficiency. However, current synaptic devices can barely detect photons and are bio‐incompatible for future all‐in‐one visual perception technology. Here, synaptic photoconductors based on an organic–inorganic hybrid structure, and composed of photosensitive bacteriorhodopsin protein layer and zinc oxide film are reported. The synaptic photoconductors demonstrate tunable synaptic plasticity with the modulation of the light illumination time and power intensity. The working mechanism of the photogating effect induced by the proton pump process of bR protein molecules is further investigated in detail. Assisting with these properties, the imaging memorization and preprocessing function are successfully emulated by the synaptic photoconductors. The prototype photosynaptic devices provide a unique opportunity to realize artificial synapses, enabling neuromorphic hardware. [ABSTRACT FROM AUTHOR]

The possibility of using semiconductor nanocrystals in photodetectors for optical detection of open flame has been explored. The spectral range boundaries of response of flame detectors have been concretized. In accordance with this, colloidal lead sulfide nanocrystals absorbing in the range of 1–1.5 µm have been synthesized. Photoresistors with different ligand compositions have been made from these particles. For the obtained samples, the current–voltage characteristics were measured and the photosensitivity and specific detectivity parameters were calculated. A theoretical estimate of the flame detection range has been made for the samples. It has been shown that a photosignal can be reliably detected at a distance of more than 80 m. [ABSTRACT FROM AUTHOR]

The properties of Pb1−xMnxTe/CdTe multilayer composite grown by molecular beam epitaxy on a GaAs substrate were studied. The study included morphological characterization by X-ray diffraction, scanning electron microscopy, secondary ion mass spectroscopy, as well as electron transport and optical spectroscopy measurements. The main focus of the study was on the sensing properties of photoresistors made of Pb1−xMnxTe/CdTe in the infrared spectral region. It was shown that the presence of Mn in the Pb1−xMnxTe conductive layers shifted the cut-off wavelength toward blue and weakened the spectral sensitivity of the photoresistors. The first effect was due to an increase in the energy gap of Pb1−xMnxTe with an increase in Mn concentration, and the second was due to a pronounced deterioration in the crystal quality of the multilayers owing to the presence of Mn atoms, as shown by the morphological analysis. [ABSTRACT FROM AUTHOR]

Metal‐semiconductor nanostructures in various configurations are extensively used in photodetection, photocatalysis, and photovoltaics. For photodetection purposes, the working principle is straightforward; on illumination, generated charge carriers in excess lead to a decrease in resistance. Notably, using an interconnected metal‐semiconductor grating, it is observed and now reported an opposite response, an increase in the resistance. Such photoresistors are fabricated through wrinkle structuring and oblique angle material deposition methods. It is found that the controlled wrinkling leads to large‐area 1D periodic structures with coexisting cracking perpendicular to the grating direction—such cracks are used as connections between the two‐point contact measurement through the associated gold layer deposition. An enhanced current reduction is further observed on photoexcitation for an additional deposition of an amorphous titania layer. Subsequently, a discussion on the mechanisms and interaction between hot electron injection, charge carrier recombination, and thermalization is presented. Supported by numerical modeling, the angle‐resolved plasmonic modes with the photoresistance can be correlated. The ease of layered deposition of the materials allows one to extend the studies on cavity‐based structures with sandwiched titania layers as hotspots. This simple, scalable, and robust fabrication method thus promises an efficient routeway toward photosensor development in which plasmon‐mediated hot electrons play a crucial role. [ABSTRACT FROM AUTHOR]

Epitaxial heterostructures of colloidal lead halide perovskite nanocrystals (NCs) with other semiconductors, especially the technologically important metal chalcogenides, can offer an unprecedented level of control in wavefunction design and exciton/charge carrier engineering. These NC heterostructures are ideal material platforms for efficient optoelectronics and other applications. Existing methods, however, can only yield heterostructures with random connections and distributions of the two components. The lack of epitaxial relation and uniform geometry hinders the structure–function correlation and impedes the electronic coupling at the heterointerface. This work reports the synthesis of uniform, epitaxially grown CsPbBr3/CdS Janus NC heterostructures with ultrafast charge separation across the electronically coupled interface. Each Janus NC contains a CdS domain that grows exclusively on a single {220} facet of CsPbBr3 NCs. Varying reaction parameters allows for precise control in the sizes of each domain and readily modulates the optical properties of Janus NCs. Transient absorption measurements and modeling results reveal a type II band alignment, where photoexcited electrons rapidly transfer (within ≈9 picoseconds) from CsPbBr3 to CdS. The promoted charge separation and extraction in epitaxial Janus NCs leads to photoconductors with drastically improved (approximately three orders of magnitude) responsivity and detectivity, which is promising for ultrasensitive photodetection. [ABSTRACT FROM AUTHOR]

The direct laser synthesis of periodically nanostructured 2D transition metal dichalcogenide (2D-TMD) films, from single source precursors, is presented here. Laser synthesis of MoS2 and WS2 tracks is achieved by localized thermal dissociation of Mo and W thiosalts, caused by the strong absorption of continuous wave (c.w.) visible laser radiation by the precursor film. Moreover, within a range of irradiation conditions we have observed occurrence of 1D and 2D spontaneous periodic modulation in the thickness of the laser-synthesized TMD films, which in some cases is so extreme that it results in the formation of isolated nanoribbons with a width of ~200 nm and a length of several micrometers. The formation of these nanostructures is attributed to the effect that is known as laser-induced periodic surface structures (LIPSS), which is caused by self-organized modulation of the incident laser intensity distribution due to optical feedback from surface roughness. We have fabricated two terminal photoconductive detectors based on nanostructured and continuous films and we show that the nanostructured TMD films exhibit enhanced photo-response, with photocurrent yield increased by three orders of magnitude as compared to their continuous counterparts. [ABSTRACT FROM AUTHOR]

Nanocrystals' (NCs) band gap can be easily tuned over the infrared range, making them appealing for the design of cost-effective sensors. Though their growth has reached a high level of maturity, their doping remains a poorly controlled parameter, raising the need for post-synthesis tuning strategies. As a result, phototransistor device geometry offers an interesting alternative to photoconductors, allowing carrier density control. Phototransistors based on NCs that target integrated infrared sensing have to (i) be compatible with low-temperature operation, (ii) avoid liquid handling, and (iii) enable large carrier density tuning. These constraints drive the search for innovative gate technologies beyond traditional dielectric or conventional liquid and ion gel electrolytes. Here, we explore lithium-ion glass gating and apply it to channels made of HgTe narrow band gap NCs. We demonstrate that this all-solid gate strategy is compatible with large capacitance up to 2 µF·cm−2 and can be operated over a broad range of temperatures (130–300 K). Finally, we tackle an issue often faced by NC-based phototransistors:their low absorption; from a metallic grating structure, we combined two resonances and achieved high responsivity (10 A·W−1 or an external quantum efficiency of 500%) over a broadband spectral range. [ABSTRACT FROM AUTHOR]

Terahertz (THz) technology has attracted significant research attention because it can be used for a host of applications, such as astronomical observations, security checks, material optimization, and biomedical treatment. In this work, we fabricate an extrinsic n-type GaAs photoconductive detector whose peak photoelectric response is demonstrated to be at about 255 μm. To improve device performance in a long-wave (>350 μm) domain and overcome the epitaxial-growth bottleneck, we designed hybrid structural GaAs-based photoconductive detectors on the surface of which we add subwavelength one-dimensional metallic gratings (i.e., with grating periods that range from 100 to 125 μm) and investigated the wavelength-selective enhancement of their absorption in the THz regime by using a finite-different time-domain simulation. The simulation results indicate that selective enhancement of antireflection and absorption occurs in the reflection and absorption spectra so that the peak wavelength of photoelectric response can be extended to over 400 μm and the thickness of absorption layer can be reduced to 50 μm. The electric-field intensity of the incident THz wave can be significantly enhanced near the interface between the metal gates and the absorption layer. This work can thus provide a potential scheme to fabricate high-performance THz detectors for numerous applications. [ABSTRACT FROM AUTHOR]

The Arduino microcontroller is currently one of the favorite tools of makers, and many teachers have used it in teaching or experiments. In addition, light-emitting diode (LED) smart lighting is the worldwide trend in lighting. There are many teaching demonstrations or applications of color addition using LEDs. Furthermore, the Internet of Things (IoT) is a popular emerging technology today, and the sensor is the most important component in the perception layer of the IoT, which makes teaching, research, or application related to sensors very important. Therefore, this study shows that an Arduino microcontroller can be used as an experimental setup for the teaching of light color mixing, light intensity detection, and ambient temperature sensing via a tricolor (red, green, and blue [RGB]) LED and two types of sensors: photoresistors and thermistors. The setup has intuitive, concrete, and multifunctional features, and is expandable, which is different from the typical experimental setup designed for only a single specific purpose. It is also suitable for students learning about light color mixing and sensor-related physics course experiments or demonstrations, whether they be in high school or college. [ABSTRACT FROM AUTHOR]

Photodetectors formed with layered two‐dimensional (2D) materials have shown significant potential for integration with photonic circuits, offering fast, high responsivity and low noise detection over a broad range of optical wavelengths. However, only preliminary trials of this concept have been performed on emerging photonics platforms such as lithium niobate on insulator (LNOI). In this study, a novel architecture consisting of ≈15 nm thick layered black phosphorus (bP) photoconductors draped over LNOI waveguides is demonstrated. The performance of these detectors is studied across the telecom bands at room temperature, and a high extrinsic responsivity of 148 mA W−1 is measured at λ = 1550 nm under low bias conditions (VDS = 0.3 V). The spectral response of the detectors is broad allowing the response of other photonic components, such as fiber‐to‐chip grating couplers, to be characterized in situ, without need to out‐couple the light. Finally, the speed of the bP detectors is found to be beyond our instrumentation, setting 100 ns as an upper‐limit rise/fall time, with the actual speed of the bP detector likely to be much faster. [ABSTRACT FROM AUTHOR]

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Perovskite photodetectors have attracted much research and attention because of their outstanding photoelectric characteristics, such as good light harvesting capability, excellent carrier migration behavior, tunable band gap, and so on. Recently, the reported studies mainly focus on materials synthesis, device structure design, interface engineering and physical mechanism analysis to improve the device characteristics, including stability, sensitivity, response speed, device noise, etc. This paper systematically summarizes the application fields and device structures of several perovskite photodetectors, including perovskite photoconductors, perovskite photodiodes, and perovskite phototransistors. Moreover, based on their molecular structure, 3D, 2D, 1D, and 0D perovskite photodetectors are introduced in detail. The research achievements and applications of perovskite photodetectors are summarized. Eventually, the future research directions and main challenges of perovskite photodetectors are prospected, and some possible solutions are proposed. The aim of the work is to provide a new thinking direction for further improving the performance of perovskite photodetectors. [ABSTRACT FROM AUTHOR]

Multiple photovoltaic (PV) modules are often used to provide enhanced harvesting capability for light energy-based Internet of Things (IoT) devices. PV modules facing multiple directions can lead to a situational energy loss when parts of the modules are shaded. To address this issue, existing solutions exploit reconfigurable PV arrays to acquire the optimal configuration in a given situation. However, conventional techniques are not energy efficient in estimating the harvesting capability of PV modules, and require high computation to find the optimal PV array at runtime. In this article, we propose PVoT, an energy-efficient reconfigurable PV array, which maximizes the harvesting energy for indoor IoT devices. To this end, we propose the use of photoresistors to estimate the harvesting capability with minimal energy overhead. We also provide hardware and software schemes, which perform event-driven light change detection in an energy-efficient way. Furthermore, we develop a power imbalance threshold metric to quickly find the optimal PV array at runtime. We implemented a prototype PVoT with off-the-shelf components and accompanying software. Experiments with the prototype hardware showed that PVoT achieves a gain of up to 23.9% in harvested energy compared to the existing directly connected PV array scheme. [ABSTRACT FROM AUTHOR]

The general fabrication process for stabilized amorphous selenium (a-Se) detectors is vacuum deposition. The evaporant alloy is typically selenium alloyed with 0.3–0.5%As to stabilize it against crystallization. During the evaporation, fractionation leads to the formation of a deposited film that is rich in As near the surface and rich in Se near the substrate. The As content is invariably not uniform across the film thickness. This paper examines the effect of non-uniform As content on the charge collection efficiency (CE). The model for the actual CE calculation is based on the generalized CE equation under small signals; it involves the integration of the reciprocal range-field product (the schubweg) and the photogeneration profile. The data for the model input were extracted from the literature on the dependence of charge carrier drift mobilities and lifetimes on the As content in a-Se1−xAsx alloys to generate the spatial variation of hole and electron ranges across the photoconductor film. This range variation is then used to calculate the actual CE in the integral equation as a function of the applied field. The carrier ranges corresponding to the average composition in the film are also used in the standard CE equation under uniform ranges to examine whether one can simply use the average As content to calculate the CE. The standard equation is also used with ranges from the spatial average and average inverse. Errors are then compared and quantified from the use of various averages. The particular choice for averaging depends on the polarity of the radiation-receiving electrode and the spatial variation of the carrier ranges. [ABSTRACT FROM AUTHOR]

Light-induced microbial electron transfer has potential for efficient production of value-added chemicals, biofuels and biodegradable materials owing to diversified metabolic pathways. However, most microbes lack photoactive proteins and require synthetic photosensitizers that suffer from photocorrosion, photodegradation, cytotoxicity, and generation of photoexcited radicals that are harmful to cells, thus severely limiting the catalytic performance. Therefore, there is a pressing need for biocompatible photoconductive materials for efficient electronic interface between microbes and electrodes. Here we show that living biofilms of Geobacter sulfurreducens use nanowires of cytochrome OmcS as intrinsic photoconductors. Photoconductive atomic force microscopy shows up to 100-fold increase in photocurrent in purified individual nanowires. Photocurrents respond rapidly (<100 ms) to the excitation and persist reversibly for hours. Femtosecond transient absorption spectroscopy and quantum dynamics simulations reveal ultrafast (~200 fs) electron transfer between nanowire hemes upon photoexcitation, enhancing carrier density and mobility. Our work reveals a new class of natural photoconductors for whole-cell catalysis. Despite enormous potential of solar-driven biocatalysis, most living systems lack photoactive proteins and require toxic and expensive synthetic materials limiting the performance. Here, a class of natural photoconductors is demonstrated through sub-picosecond heme-to-heme electron transfer in bacteria-produced protein nanowires. [ABSTRACT FROM AUTHOR]

The properties of Pb1−xMnxTe/CdTe multilayer composite grown by molecular beam epitaxy on a GaAs substrate were studied. The study included morphological characterization by X-ray diffraction, scanning electron microscopy, secondary ion mass spectroscopy, as well as electron transport and optical spectroscopy measurements. The main focus of the study was on the sensing properties of photoresistors made of Pb1−xMnxTe/CdTe in the infrared spectral region. It was shown that the presence of Mn in the Pb1−xMnxTe conductive layers shifted the cut-off wavelength toward blue and weakened the spectral sensitivity of the photoresistors. The first effect was due to an increase in the energy gap of Pb1−xMnxTe with an increase in Mn concentration, and the second was due to a pronounced deterioration in the crystal quality of the multilayers owing to the presence of Mn atoms, as shown by the morphological analysis.

Background and Objectives: The use of two-dimensional materials in the photodetector fabrication has received much attention in recent years. Graphene is a two-dimensional material that has been extensively researched to make photodetectors. The responsivity of graphene photodetectors was limited by the low optical absorption in graphene (~2.3% for single layer graphene). Therefore, graphene along with other materials has been used to fabricate a photodetector with the desired properties. The graphene is used for the improvement of the silicide platinum photodetector. Methods: The platinum silicide photodetector with graphene has been experimentally fabricated and characterized, and all steps of the device fabrication and the characterization are completely provided in addition to required equations for device analysis is completely provided. A graphene layer is transferred on the platinum silicide layer, and the graphene layer creates the photoconductor gain in the platinum silicide photodetector. Results: In the proposed device, near-infrared light is detected in the platinum silicide, and by placing a layer of graphene on the platinum silicide, the optical current and responsivity increase compared to the platinum silicide photodetector without graphene. Experimental results show that the optical current, external quantum efficiency, and responsivity increase in the platinum silicide photodetector with graphene. The graphene not only functions as the charge transport channel, but also works as a photoconductor. Conclusion: The optical current and responsivity are increased by the platinum silicide photodetector with graphene. In our photodetector, the highest responsivity is 120 mA/w in the 1310 nm wavelength, and the optical current is 100 nA at the applied voltage of 8 V. Our photodetector has optical current, responsivity, and external quantum efficiency twice as much as platinum silicide photodetector. Experimental results show the good performance of graphene with platinum silicide photodetector. [ABSTRACT FROM AUTHOR]

92 A. Abbes, P.-K. Lu, P. Nouvel, et al., "280 GHz radiation source driven by a 1064nm continuous-wave dual-frequency vertical external cavity semiconductor laser", in 2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz), Chengdu, China, IEEE, 2021, pp. 1-2. 93 P.-K. Lu and J. Mona, "A continuous-wave terahertz self-heterodyne spectroscopy system without using short-carrier-lifetime photoconductors", in 2021 46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz), San Jose, California, US, IEEE, 2021, pp. 1-2. 94 W. Wang, P.-K. Lu, A. K. Vinod, et al.., "High spectral purity chip-scale tunable THz radiation source", in CLEO: Applications and Technology, Chengdu, China, Optical Society of America, 2021, p. ATu2T-3. 95 D. Turan, N. T. Yardimci, and M. Jarrahi, "Plasmonics-enhanced photoconductive terahertz detector pumped by Ytterbium-doped fiber laser", Opt. The radiated power spectral density, however, becomes independent of the recombination time in the high frequency limit, HT ht . Equivalently, beyond the lifetime (or transit-time) cut-off frequency, its value also rolls off as HT ht . [Extracted from the article]

[Display omitted] • A low cost, multi-color, room-temperature, and easily-feasible mid-Infrared photoconductor with distinct output currents has been investigated which can be synthezied by the solution process method. • Coupled rate equations and three-dimensional Schrodinger-Poisson equations have been developed and solved self-consistently to model the proposed device theoretically. • The mechnisim of the photocurrent generation is the resonant tunneling effect through distict selective energy contacts which reduces the dark current significantly, so high specific detectivies have been attained. This report paves the way for low cost, multi-color, room-temperature, and easily-feasible mid-IR photodetector with distinct output currents. The proposed device is designed and simulated to be fabricated by the solution-process technology thanks to its simplicity and fabrication ease, room-temperature operation capability, low production cost, and excellent photoelectric properties. In this approach, the proposed structure is composed of an array of n × n pixels, where each pixel is designed to enable multi-wavelength detection. The absorber layer consists of different sized quantum dots that absorb distinct wavelengths simultaneously through interband transitions in the mid-infrared region. Selective energy contacts based on quantum well structures are designed to be deposited on interdigitated contacts as a means of extracting the stimulated carriers from the absorber layers to the metal contacts. Through resonant tunneling, the excited carriers are transferred, which generates the output photocurrent and significantly reduces the dark current. In order to model the designed multi-color photoconductor, coupled rate equations and three-dimensional Schrodinger-Poisson equations have been developed and solved self-consistently. As a way of demonstrating the validity of the introduced model, a experimentally fabricated photoconductor and a theoretically modeled photodetector using the nonequilibrium Green's function (NEGF) model have been simulated; the comparison between the simulation results is quite satisfactory. In order to simplify the theoretical model, two different sizes of InSb/ZnSe core/shell quantum dots have been considered in the theoretical model to detect two MIR wavelengths (3 µm and 4 µm) of the incident light. Simulation results indicate that the peak responsivities are about 3.3(A/W) and 6(A/W), and the high specific detectivities D* are about 9 × 1010(cm.Hz1/2W−1) and 15 × 1010(cm.Hz1/2W−1) for the wavelengths of 4 µm and 3 µm, respectively. [ABSTRACT FROM AUTHOR]

Solar-blind UV photodetectors are extensively applied in both military and civilian domains. In this work, a high-performance Pt/Ga 2 O 3 /p-Si Schottky emitter solar-blind UV bipolar junction phototransistor is demonstrated. It exhibits a peak responsivity (@246 nm) of 1632.8 A/W under a bias of 5 V. This responsivity is significantly enhanced compared to the Al/Ga 2 O 3 /p-Si heterojunction photodetector, while its response speed remains largely unchanged. Additionally, the device demonstrates excellent solar-blind UV spectral selectivity, with a solar-blind UV to visible-blind UV rejection ratio (R 246 nm / R 365 nm) reaching 2.4×104. This work provides new insights into the design and fabrication of high-performance Ga 2 O 3 -based solar-blind UV photodetectors. • Ga 2 O 3 films were grown on the p-Si by molecular beam epitaxy. • A high-performance solar-blind UV bipolar junction phototransistor was demonstrated for the first time. • The photodetector adeptly balances high gain with rapid response compared with photoresistors. • The photodetector demonstrates a high solar-blind to visible-blind UV rejection ratio of 2.4×104. [ABSTRACT FROM AUTHOR]

• We prepare photoconductive films composed of PbS quantum dots with multiple excitonic peaks. • Mixed quantum dots films shows adjustable absorbance. • Mixed quantum dots films were successfully used to fabricate dual-band photodetectors. • Photoconductors based on mixed quantum dots film have a significantly higher responsivity. Dual-band infrared detection offers enhanced spectral information crucial for improved target identification. Traditional dual-band infrared photodetectors have often relied on expensive epitaxial growth bulk materials, limiting their widespread use in civilian applications. Colloidal quantum dots present an affordable alternative for dual-band infrared detection, owing to their spectral tunability and solution processability. In this study, we have developed an approach utilizing mixed lead sulfide quantum dot films to achieve dual-band infrared detection spanning the NIR (Near Infrared) and SWIR (Short Wave Infrared) ranges. These films exhibit a broad absorption spectrum, ranging from 400 to 1600 nm. When operating within the near-infrared band, the device based on mixed quantum dot films demonstrates an responsivity of 0.18A/W and specific detectivity of 2.38 × 109 c m ∙ H z 1 / 2 / W near 900 nm.While operated in the SWIR band, the detector has responsivity of 0.17A/W and specific detectivity of 2.11 × 109 c m ∙ H z 1 / 2 / W near 1600 nm. [ABSTRACT FROM AUTHOR]

Herein, near infrared light‐sensing organic light‐dependent resistors (NIR–OLDRs) is reported, that are fabricated with a planar geometry by employing poly[{3‐(5‐(7‐methyl‐5,6‐bis(octyloxy)benzo[c][1,2,5]thiadiazol‐4‐yl)thiophen‐2‐yl)‐6‐(5‐methylthiophen‐2‐yl)}‐co‐{2,5‐bis(2‐octyldodecyl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione}] (PDPP‐8OBT) as an active layer. The PDPP‐8OBT polymer, which is synthesized by the Stille coupling reaction of corresponding monomers, shows a broad absorption up to ≈1000 nm (wavelength) and good thermal stability with a glass transition temperature of >200 °C. A high‐power laser diode, which emits a monochromatic NIR light (wavelength = 905 nm) for light detection and ranging (LiDAR) systems, is used to examine the characteristics of NIR–OLDRs. Results show that the present NIR–OLDRs can successfully detect the 905 nm NIR light and their electrical resistance (and photocurrent) is sensitive to the incident intensity of NIR light. In particular, for both regular and semitransparent devices, the best NIR light‐sensing performances are achieved by device annealing at 150 °C (change of resistance = 34.5%) due to the increased crystallinity of PDPP‐8OBT films. The present NIR–OLDRs exhibit excellent sensing stability upon optical on/off modulations of NIR light (905 nm). [ABSTRACT FROM AUTHOR]

Combined hybrid nanocomposites based on PVDF+CdS/ZnS were developed and studied. The structure of nanocomposites was characterized by XRD, SEM, EDS, UV- spectroscopic techniques. XRD analysis shows that the incorporation of CdS and ZnS semiconductor nanoparticles leads to a decrease in the fraction of the α-phase and an increase in the β-phase of the polymer. It was determined that the bandgap of the nanocomposite based on PVDF+1%CdS/ZnS, PVDF+3%CdS/ZnS, PVDF+5%CdS/ZnS and PVDF+10%CdS/ZnS is 5.3 eV, 5.0 eV, 4.3 eV and 3.1 eV, respectively. The photoluminescence properties of the polymer nanocomposites were also examined. It was established that for these nanocomposites, the introduction of the CdS/ZnS nanoparticles into the polymer matrix leads to expanding of the spectral-sensitive region of the PL spectrum of the nanocomposites. It was shown that combine hybrid nanocomposites on the base of PVDF+CdS/ZnS emit the light at the wide-wavelength-range. According to this feature, it is possible to use these nanocomposites in various fields of optoelectronics as the active elements of solar batteries, cells, displays, converters, etc. The photosensitivity of the PVDF+CdS/ZnS films was discovered. It gives the possibility to use these materials as thermoplastic photoresistors. [ABSTRACT FROM AUTHOR]

At present, self-repairing, intelligent materials are being considered as future material. In this perspective, the electroactive materials are unique for their adaptability, sharp response time, control over the system, quick response rate, low power consumption, and compactness. The electroactive materials include electroactive polymers (EAPs), piezoelectric materials, electroactive gels, and fullerene compounds. The photonic interaction of light with the electroactive material converts light energy into mechanical energy and leads to multi-directional applications. Contemporarily with increased interest and emphasis on 'green' technological solutions, efforts are focussed on utilizing these electroactive materials with light energy. Corresponding to this, biomimetic and artificial intelligence are advancing to develop various optoelectronic devices, energy conversion and storage devices, photoresistors, vehicle components, sensors, robots, and medical devices. A better understanding of such light illumination with electroactive materials and prospective applications contributes to the planning of beneficial smart materials. Hence, this review article focusses on the interaction of light with different electroactive materials, their applications, and prospects of the current and future investigations. [ABSTRACT FROM AUTHOR]

Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in oxygen or halide atmospheres is necessary to endow them photo-sensitivity. This paper proposes a universal approach to improve optoelectrical properties for thin film photoresistors (TFPs) by quick-oxygen-sensitizing the doped chalcogenide material PbSnSe with ion implantation. Compared with the as-deposited film, the implanted film exhibits much more uniform image, higher optical absorption, broader optical band gap and better photoelectronic properties. In sensitized PbSnSe TFPs, the PbSnO3 phase formed, which can trap minority carriers, enabling enhanced photoconduction. We also demonstrate the performance of sensitized PbSnSe TFPs with ultraquick and stable photo-response for IR irradiation. The photosensitivity of the sensitized PbSnSe TFPs was about 4.1%, which is about 41.5% higher than that of its as-deposited counterpart. Moreover, the photosensitivity attenuation was restricted by sensitization. The results indicate promising potentials for sensitized chalcogenide platforms, and the developed strategy can be applied for high-performance chalcogenide optoelectronics. [ABSTRACT FROM AUTHOR]

Purpose: Scintillators and photoconductors used in energy integrating detectors (EIDs) have inherent variations in their imaging response to single‐detected X‐rays due to variations in X‐ray energy deposition and secondary quanta generation and transport, which degrades DQE(f). The imaging response of X‐ray scintillators to single X‐rays may be recorded and studied using single X‐ray imaging (SXI) experiments; however, no method currently exists for relating SXI experimental results to EID DQE(f). This work proposes a general analytical framework for computing and analyzing the DQE(f) performance of EIDs from single X‐ray image ensembles using a spatial frequency‐dependent pulse‐height spectrum. Methods: A spatial frequency (f)‐dependent gain, g∼(f)$\tilde{g}(f)$, is defined as the Fourier transform of the imaging response of an EID to a single‐detected X‐ray. A f‐dependent pulse‐height spectrum, Pr[g∼(f)]$\Pr [\tilde{g}(f)]$, is defined as the 2D probability density function of g∼(f)$\tilde{g}(f)$ over the complex plane. Pr[g∼(f)]$\Pr [\tilde{g}(f)]$ is used to define a f‐dependent Swank factor, AS(f), which fully characterizes the DQE(f) degradation due to single X‐ray noise. AS(f) is analyzed in terms of its degradation due to Swank noise, variations in the frequency‐dependent attenuation of |g∼(f)|$| {\tilde{g}(f)} |$, and noise in argg∼(f)$\arg \tilde{g}(f)$ which occurs due to variations in the asymmetry in each single X‐ray's imaging response. Three example imaging systems are simulated to demonstrate the impact of depth‐dependent variation in g∼(f)$\tilde{g}(f)$, remote energy deposition, and a finite number of secondary quanta, on Pr[g∼(f)]$\Pr [\tilde{g}(f)]$, AS(f), MTF(f), and NPS(f)/NPS(0), which are computed from ensembles of single X‐ray images. The same is also demonstrated by simulating a realistic imaging system; that is, a Gd2O2S‐based EID. Using the latter imaging system, the convergence of AS(f) estimates is investigated as a function of the number of detected X‐rays per ensemble. Results: Depth‐dependent g∼(f)$\tilde{g}(f)$ variation resulted in AS(f) degradation exclusively due to depth‐dependent optical Swank noise and the Lubberts effect. Conversely, the majority of AS(f) degradation caused by remote energy deposition and finite secondary quanta occurred due to variations in argg∼(f)$\arg \tilde{g}(f)$. When using input X‐ray energies below the K‐edge of Gd, variations in the frequency‐dependent attenuation of |g∼(f)|$| {\tilde{g}(f)} |$ accounted for the majority of AS(f) degradation in the GOS‐based EID, and very little Swank noise and variations in argg∼(f)$\arg \tilde{g}(f)$ were observed. Above the K‐edge, however, AS(f) degradation due to Swank noise and variations in argg∼(f)$\arg \tilde{g}(f)$ greatly increased. The convergence of AS(f) was limited by variation in argg∼(f)$\arg \tilde{g}(f)$; imaging systems with more variation in argg∼(f)$\arg \tilde{g}(f)$ required more detected X‐rays per ensemble. Conclusions: An analytical framework is proposed that generalizes the pulse‐height spectrum and Swank factor to arbitrary f. The impact of single X‐ray noise sources, such as the Lubberts effect, remote energy deposition, and finite secondary quanta on detector performance, may be represented using Pr[g∼(f)]$\Pr [\tilde{g}(f)]$, and quantified using AS(f). The approach may be used to compute MTF(f), NPS(f), and DQE(f) from ensembles of single X‐ray images and provides an additional tool to analyze proposed EID designs. [ABSTRACT FROM AUTHOR]

Most of the plants require just the right amount of water. Any quantity of water less or more than required for a given type of plant is not desirable. In this project, two sensors are used to spray the right quantity of water into the plant pot. A soil moisture measuring sensor and photoresistor sensor are employed to measure the water content in the pot's soil and the radiation level of the sun respectively. A simple linear proportionate formula is employed to calculate the amount of water to be sprayed into the plant pot using the input values of the two above mentioned sensors. A simple motor is actuated to compress the sprayer for the calculated duration of time based on the above mentioned formula. [ABSTRACT FROM AUTHOR]

We report on the photoresponse of AlGaN/GaN high electron mobility transistors to the THz radiation of low (15 mW/cm²) and high (up to 40 kW/cm²) intensities. We show that the response can be described by the Dyakonov-Shur theory in the whole range of radiation intensity. At low intensities, the photoresponse is linear in radiation intensity. Under intense laser radiation, we observe a saturation at intensities >20 kW/cm². We explain our results by the change of the channel conductivity under the influence of strong THz field. This mechanism of photoresponse saturation, which is due to the mobility decrease in high ac electric field, should exist for any type of field effect transistor detectors. [ABSTRACT FROM AUTHOR]

Avalanche amorphous selenium (a-Se) in a layer of High Gain Avalanche Rushing Photoconductor (HARP) is being investigated for its use in large area medical imagers. Avalanche multiplication of photogenerated charge requires electric fields greater than 70 V μm-1. For a-Se to withstand this high electric field, blocking layers are used to prevent the injection of charge carriers from the electrodes. Blocking layers must have a high injection barrier and deep trapping states to reduce the electric field at the interface. In the presence of a defect in the blocking layer, a distributed resistive layer (DRL) must be included into the structure to build up space charge and reduce the electric field in a-Se and the defect. A numerical charge transport model has been developed to optimize the properties of blocking layers used in various HARP structures. The model shows the incorporation of a DRL functionality into the p-layer can reduce dark current at a point defect by two orders of magnitude by reducing the field in a-Se to the avalanche threshold. Hole mobility in a DRL of ~10-8 cm2 V-1 s-1 at 100 V μm-1 as demonstrated by the model can be achieved experimentally by varying the hole mobility of p-type organic or inorganic semiconductors through doping, e.g., using Poly(9-vinylcarbozole) doped with 1%-3% (by weight) of poly(3-hexylthiopene). [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskites exhibit superior optoelectrical properties and have been widely used in photodetectors. Perovskite photodetectors with excellent detectivity have great potential for developing artificial photonic synapses which can merge data transmission and storage. They are highly desired for next generation neuromorphic computing. The recent progress of perovskite photodetectors and their application in artificial photonic synapses are summarized in this review. Firstly, the key performance parameters of photodetectors are briefly introduced. Secondly, the recent research progress of photodetectors including photoconductors, photodiodes, and phototransistors is summarized. Finally, the applications of perovskite photodetectors in artificial photonic synapses in recent years are highlighted. All these demonstrate the great potential of perovskite photonic synapses for the development of artificial intelligence. [ABSTRACT FROM AUTHOR]

The photoresponse of antenna-coupled Hg1-xCdxTe (x ≈ 0.201) narrow-gap epitaxially grown photoconductors with normal band ordering having large spin–orbit coupling and being irradiated by the normal to the photoconductor surface terahertz (THz) radiation (linearly or circularly polarized), is investigated at T = 80 and 300 K. The oscillations of polarized photoresponse in biased and unbised structures were revealed. In experiments, Hg1-xCdxTe layers (point group) grown on (013) GaAs substrates were used. In biased structures, to the ordinary charge current and Rashba spin splitting current in zero electric field, an additional polarized current, which grows with the external electric field strength, arises. Presumably, the oscillating photoresponses under polarized THz radiation in these unbiased and biased structures are connected with the circular and linear photogalvanic effects without and with an external electric field. The observed features of the polarized dependent photoresponse can be important for spintronics applications at elevated temperatures. [ABSTRACT FROM AUTHOR]

The possibility of using silicon with the nanoclusters of manganese atoms for creating photoresistors in the spectral region λ = 1.2–3 μm is shown. It is found that such photodetectors possess a threshold sensitivity of about 10–11 W at a wavelength of 1.55 μm. The quantum efficiency at a wavelength of 2 μm exceeds 10% and is 0.1% at a wavelength of 2.5 μm, which makes it possible to use the impurity photosensitivity of silicon with the nanoclusters of manganese atoms for creating high-resolution array photodetectors operating in the spectral region of up to 2.5 μm. [ABSTRACT FROM AUTHOR]

The electric-field dependence of photocarrier generation efficiency has been investigated in several different types of organic photoconductor for electrophotography to elucidate the controlling factors of light-to-electrical energy conversion. The rate-determining step in generating photocarriers has been considered to be the charge transfer between two neighboring molecules. Overall photocarrier generation efficiency has been determined using the charge transfer velocity at the ratedetermining step as a function of electric-field-dependent activation energy, which is influenced by the symmetry factor α and the energy gap ΔE. The formula used successfully fits the experimental data for different types of organic photoconductor over a wide field strengths range. From the fitting results of high-sensitivity photoconductors, the zero-field activation energy is small and the reactant lifetime is long. In addition, ΔE is zero, which implies that the hole-electron interaction in the reactant is negligible at the rate-determining step. In contrast, for low-sensitivity photoconductors, the zero-field activation energy is large and the reactant lifetime is short; however, ΔE<0 and α>0.5, which suggest that the hole-electron interaction is not negligible. Consequently, the proposed formula well explains the electric-field dependence of photocarrier generation efficiency on the basis of its controlling factors. [ABSTRACT FROM AUTHOR]

Photodetectors based on a heterojunction between graphene and photoactive layers have attractive features such as high responsivity and spectral sensitivity, but their narrow bandwidth originating from charge trapping is a major drawback. Here, it is demonstrated that the bandwidth of a graphene–organic hybrid photoconductor, where a planar bilayer of fullerene (C60) and zinc phthalocyanine (ZnPc) is in contact with the graphene layer, can be significantly increased by doping the C60 layer with ZnPc. The bandwidth, which increases with the doping concentration, is found to be more than two orders of magnitude higher at 40 vol% doping than that of the undoped device. Consequently, the 40%‐doped device has a fall time of the photocurrent transient of 19 μs, which is ≈300 times smaller than that of the undoped device (5.8 ms). Based on the model developed to analyze the electron transfer processes between the graphene and C60 layers, the increased bandwidth is attributed to the reduced electron lifetime in the C60 trap state by recombination with holes photogenerated in the ZnPc domains in the C60 layer. [ABSTRACT FROM AUTHOR]