Photosensitive Devices Research Articles

Fully Optical-Driving Ionotronic InGaZnO4 Phototransistor for Gate-Tunable Bidirectional Photofiltering and Visual Perception

Recently, fully optical-driving neuromorphic devices have attracted growing interest. However, the current device faces great challenges due to the lack of negative photoconductivity materials, which seriously hinders the further development of the visual perceptual applications using photosensitive device. Here, we propose an ionotronic neuromorphic InGaZnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> phototransistor to establish a fully optical-driving artificial neural network. Optical neuronal paired-pulse facilitation can be switched to optical depression characteristics by tuning the gate bias more negatively through the ion-coupling bioelectrolyte. Moreover, the biological high-pass, low-pass, and band-stop photofilter behaviors can be successfully mimicked in such an all-in-one phototransistor. Finally, a fully optical-driving artificial neural network is constructed to perform artificial visual perception with an accuracy of ~90%. This device may open new avenues for the fascinating applications, such as artificial visual system, intelligent bionic robots, and smart photoelectric devices.

Novel optical temperature and phase change sensor based on the response of hydroxypyrene to sucrose in water ice

A novel optical temperature sensor based on the protonation states of 8- hydroxypyrene-1,3,6-trisulfonic acid trisodium, also known as pyranine, is developed and characterized. When water freezes and becomes ice, impurities create small pockets of liquid water, the sizes of which are dependent on temperature. Pyranine and sucrose are added to water as it freezes to create these pockets. Water of solvation molecules surrounding sucrose create a change in the ratio of protonated to deprotonated pyranine as a function of sucrose concentration within the liquid pockets. The protonated and deprotonated forms of pyranine emit light at 440 nm and 511 nm, respectively, which is captured with a photosensitive device. These phenomena are leveraged to create a temperature and phase change sensor within ice. The sensor is illuminated using 365 nm illumination and the fluorescence intensity ratio of the 44nm and 511nm emission peaks of pyranine is studied as a function of temperature and phase change in the range 258–293 K. By using this ratio, the temperature and phase changes within an ice block are measured in a temporally and spatially resolved manner. The temperature sensitivity within the ice phase is − 9.2 ± 0.1% K−1 which is better than conventionally used fluorescence-based temperature sensors. The pyranine and sucrose sensor is a promising candidate for an optical temperature sensor with high sensitivity within bulk ice.

Strong interfacial coupling in vertical WSe2/WS2 heterostructure for high performance photodetection

Two-dimensional van der Waals (vdWs) heterostructures have shown great potential in the field of electronic and optoelectronic applications over the recent decade. However, the controlled preparation of high-quality vdWs heterostructures remains a great challenge ascribing to the incompatibility of different material synthesis processes. Here, we report a two-step chemical vapor deposition method for the growth of high quality WS2 on a WSe2 template with a very low temperature of ∼550 °C, where WO3 nanosheets formed in the first step are further employed as the precursor for synthesis of the top WS2 layer in the second step. Such low growth temperatures in the second step also enable the effective protection of bottom WSe2 during the WS2 growth process and, therefore, result in high-quality WSe2/WS2 heterostructures. Photoluminescence characterizations are further conducted, where significant interlayer exciton emission is observed, indicating strong interlayer coupling in the heterostructure. Based on the obtained WSe2/WS2 heterostructure, dual-channel photosensitive devices were further designed and systematically studied, where high photoresponsivity (3 A/W) as well as fast response speed (&amp;lt;1 ms) are obtained. The developed WO3-assisted growth technique would provide an effective reference for the controlled synthesis of high quality vdWs heterostructures and promote further applications in high-performance optoelectronic devices.

Electric field modulated photoluminescence in ferroelectric ceramics for photosensitive device applications

The degree of freedom controlled by electronic excitations in ferroelectrics provides innovative opportunities for information processing and optoelectronics. In the current work, electrically modulated photoluminescence (PL) has been demonstrated in Pb1-x(Li0.5Bi0.5)x(Zr1-yTiy)O3 (PLBZT) for x = 0.3–0.5 and y=0.80, respectively. The primary approach was made directly to modulate the PL property by applying an external electric field in an in-situ way. However, the modulation of PL is possible in perovskite oxides when the distortion of structural symmetry arose under external electrical bias in particularly ferroelectrics, implying reversible and dynamic tuning of PL emission. Hence, there is emergence of new channels where radiative and/or forbidden transitions arise from the positional disorder of the system under the application of an external electric field. These studies establish the realization of tunable PL ferroelectric ceramics with high repeatability, flexibility, and faster response towards designing advanced light switching devices.

Tuning the electronic and optical properties of two-dimensional hydrogenated c-BN nanosheets by Be and C dopants and vacancy defects

• Dopants and defects of UHBNs could tailor the electronic properties with narrow band gaps. • Antisite defects will be more likely to occur in experimental process. • Faster speed of spread in UHBNs than bulk due to low refractive index. • The visible light protection of new 2D structures have the potential to photosensitive devices. Substitutional and interstitial beryllium (Be) and carbon (C) dopants, vacancies and anti-vacancy defects in two-dimensional (2D) ultrathin hydrogenated cubic BN (c-BN) nanosheets (UHBNs) were studied using a first-principles method. Charge redistribution provides opportunities to use appropriate dopants and defects to redistribute charge and tailor the electronic properties of UHBNs to obtain p -/ n -type semiconductors with narrow band gaps. Anti-vacancy defects have lower energy than the vacancy defects, which means that in the experimental synthetic preparation process, dislocation occupancy between atoms will be more likely to occur. The refractive index is lower, the speed of spread in these materials is expected to be faster than that in bulk BN, and the region of absorption shifts from ultraviolet to visible light. Our results present an exciting opportunity for making ultrathin BN nanosheets for next-generation optoelectronic nanomaterials.

Investigation of the Influence of the Purity of the Silicon Surface on its Wettability

Silicon is the basic material of microelectronics. It is made of rectifier, pulsed, microwave diodes, low frequency and high frequency, powerful and low-power bipolar transistors, field-effect transistors, charge-coupled devices. Silicon manufacturing the majority of diodes and thyristors. Silicon is widely used for the production of photosensitive devices: photodiodes and phototransistors. In addition, the silicon used to manufacture solar panels. Therefore, the study of the properties of silicon is relevant. In this study we investigated the influence of small doses of sodium chloride in water at an angle of draining the water droplets from the surface of the silicon. Surface wettability was determined by the following method. The sample was applied a drop of water of constant volume and inclination of the sample was recorded, the angle θ at which the drop began to drain from the surface found that small doses of NaCl in water does not affect the angle of motion of the drops.

Synthesis and characterization of all-inorganic (CsPbBr3) perovskite single crystals

This work investigates the synthesis of Cesium (Cs) based all-inorganic (CsPbBr3) perovskite single crystals (PSCs) at low temperatures (45 °C) for application in photosensitive devices.

Insight into charge transportation in cadmium based semiconducting organic-inorganic hybrid materials and their application in the fabrication of photosensitive Schottky devices.

A coordination polymer (1) and a trinuclear complex (2) have been synthesized using a compartmental N2O2O2' donor Schiff base ligand. Both complexes are characterized using different spectroscopic techniques and their structures are determined using single crystal X-ray diffraction analyses. Energies associated with different non-covalent (S⋯O chalcogen bonds, C-H⋯H-C, C-H⋯I and C-H⋯π) interactions in the solid state of both complexes have been calculated using the Turbomole program. Investigations of electrical conductivity and photosensitivity of both complexes reveal that suitable Schottky diode devices could be fabricated from both complexes. The current vs. voltage plots of the complex based devices have been used to calculate the conductivity under dark and irradiation conditions. In both complexes the charge transportation mainly occurs through space which involves the hopping process. Standard band theory has been used to compare the experimental and theoretical results of optoelectronic measurements. The calculations confirm that both are direct band gap (2.78 and 3.30 eV) semiconductors and that complex 1 exhibits a lower band gap, in line with the experimental results (3.21 and 3.43 eV in 1 and 2, respectively).

Plasmon-enhanced photoresponse of single silver nanowires and their network devices.

The photo-bolometric effect is critically important in optoelectronic structures and devices employing metallic electrodes with nanoscale features due to heating caused by the plasmonic field enhancement. One peculiar case is individual silver nanowires (Ag NWs) and their networks. Ag NW-networks exhibit excellent thermal, electrical, and mechanical properties, providing a simple yet reliable alternative to common flexible transparent electrode materials used in optoelectronic devices. To date, there have been no reports on the photoresponse of Ag NWs. In this study, we show that single Ag NWs and networks of such Ag NWs possess a significant, intrinsic photoresponse, thanks to the photo-bolometric effect, as directly observed and measured using scanning photocurrent microscopy. Surface plasmon polaritons (SPPs) created at the contact metals or plasmons created at the nanowire-metal structures cause heating at the junctions where a plasmonic field enhancement is possible. The local heating of the Ag NWs results in negative photoconductance due to the bolometric effect. Here an open-circuit response due to the plasmon-enhanced Seebeck effect was recorded at the NW-metal contact junctions. The SPP-assisted bolometric effect is found to be further enhanced by decorating the Ag NWs with Ag nanoparticles. These observations are relevant to the use of metallic nanowires in plasmonic applications in particular and in optoelectronics in general. Our findings may pave the path for plasmonics-enabled sensing without spectroscopic detection.

Photodetector devices based on PIN and barrier structures &#x0D; of the mid-wave IR range of the spectrum

Multilayer structures based on the antimonide group materials with absorber layers InSb or AlxIn1-XSb, and XBn-structures with AlxIn1-XSb barrier layer (InSb/AlxIn1-XSb/InSb), designed for the manufacture of advanced photosensitive devices detecting radiation in the medium-wave infrared (IR) range (MWIR), have been developed and investigated. Various topology photosensitive elements (PSE) with absorbing layers InSb or AlxIn1-XSb were fabricated on the basis of MBE-grown p–i–n and barrier structures. It is shown that wideband ternary al-loys AlxIn1-XSb are considered as an alternative to the narrowband binary compound InSb, since, due to wide-band material properties, photodiodes based on AlxIn1-XSb have lower dark currents, and, consequently, noise. The average values of detectivity D* and noise-equivalent temperature difference (NETD) have been measured for various topology photodetectors, so D* was more than 1011 cmW-1Hz1/2 in p–i–n-structures, and D* exceed of 1012 cmW-1Hz1/2 in barrier structures.

Combining Modulated Techniques for the Analysis of Photosensitive Devices.

Small-perturbation techniques such as impedance spectroscopy (IS), intensity-modulated photocurrent spectroscopy (IMPS), and intensity-modulated photovoltage spectroscopy (IMVS) are useful tools to characterize and model photovoltaic and photoelectrochemical devices. While the analysis of the impedance spectra is generally carried out using an equivalent circuit, the intensity-modulated spectroscopies are often analyzed through the measured characteristic response times. This makes the correlation between the two methods of analysis generally unclear. In this work, by taking into consideration the absorptance and separation efficiency, a unified theoretical framework and a procedure to combine the spectral analysis of the three techniques are proposed. Such a joint analysis of IS, IMPS, and IMVS spectra greatly reduces the sample space of possible equivalent circuits to model the device and allows obtaining parameters with high reliability. This theoretical approach is applied in the characterization of a silicon photodiode to demonstrate the validity of this methodology, which shows great potential to improve the quality of analysis of spectra obtained from frequency domain small-perturbation methods.

Theoretical studies on the optical properties of group-III elements doped SiCNTs

Silicon carbide nanotubes (SiCNTs) have broad application prospects in optoelectronic devices. Based on first principles calculation, the influence of group III elements X (X = B, Al, Ga and In) doping on the optical properties of SiCNTs was studied. At 250–620 nm, because the hole concentration of X C -SiCNTs (when C is substituted) is less than that of X Si -SiCNTs (when Si is substituted), the minority carrier lifetime is longer than that of X Si -SiCNTs, therefore, the absorption peak of X C -SiCNTs is low and wide, while that of X Si -SiCNTs is high and narrow. Starting from 400 THz to 500 THz, with the increase of photo-generated carriers, the photoconductivity of X Si -SiCNTs and X C -SiCNTs increases, reaching the maximum at 700–800 THz. As the recombination rate increases, the conductivity begins to decrease, and it drops to a minimum near 1000 THz. Both dielectric constant and reflectivity show that SiCNTs doped with Si sites exhibit metallic characteristics at 340–380 nm. • Differences in optical properties caused by substitution of C and Si atoms by group III in SiCNTs were investigated. • At 250~620nm, the absorption peak of X C -SiCNTs is low and wide, while that of X Si -SiCNTs is high and narrow. • With the increase of electrons, the photoconductivity of doped SiCNTs increases, reaching the maximum at 700~800THz. • Both permittivity and reflectivity show that SiCNTs doped with Si sites exhibit metallic characteristics at 340~380nm. • The results show that SiCNTs can be used in photodetection devices and photosensitive semiconductor devices.

Polyvinylalcohol (PVA)-Assisted Exfoliation of ReS2 Nanosheets and the Use of ReS2-PVA Composites for Transparent Memristive Photosynapse Devices.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant attention for their outstanding optoelectrical properties. Unlike most TMDs with layer-dependent photoresponsivity, rhenium disulfide (ReS2) shows excellent thickness-independent photoresponsivity. Herein, we show a surfactant-free polyvinyl alcohol (PVA)-assisted exfoliation method for 2D-TMDs in aqueous solution and a transparent photosensitive memristor synapse device based on ReS2 nanosheets composited with PVA. ReS2 nanosheets are obtained via PVA-assisted exfoliation. After exfoliation, the ReS2-PVA dispersion solution is spin-coated on a substrate and dried to form a nanocomposite film without additional processing. Transparent memristors are then fabricated on plastic or glass substrates to demonstrate the applicability of the ReS2-PVA film. The devices show "write once, read many" memory behavior with a high ON/OFF current ratio (1.0 × 104 at 0.5 V) during electrical operation. In the high resistive state, synaptic functions with long-term memory behavior are successfully mimicked by applying photonic stimuli to the transparent ReS2-PVA memristors. The excitatory postsynaptic current stimulated by the photosignal is gradually reduced by electric stimuli. The proposed PVA-assisted exfoliation method is cost-effective, environmentally friendly, and applicable to various TMD nanomaterials. Furthermore, the ReS2-PVA nanocomposite film obtained via a simple solution-based process demonstrates excellent photosynaptic behavior.

Sensitive and Repeatable Photoinduced Luminescent Radicals from A Simple Organic Crystal

AbstractPhotoinduced organic radicals are important for chemical and physical processes of organic materials, which are extensively investigated and applied in organic synthesis, photoelectronic devices and biotechnology. However, there are rare reports of the luminescence for these photoinduced radicals, especially in the condensed state. Herein, an unexpected and interesting luminescent radical is described, which can be rapidly and reversibly generated from a simple organic crystal by gentle light irradiation in air. It was revealed that the twist and asymmetric conformation of isolated molecule in its crystal with only weak C−H⋅⋅⋅π intermolecular interactions, which led to the generation of such photoinduced luminescent radicals. In addition, dual‐channel photosensitive device with rapid response and well repeatability can be obtained based on the thin film of this organic crystal, showing both photoswitching on luminescence and conducting.

Photochromic holo-cellulose wood-based aerogel grafted azobenzene derivative by SI-ATRP

Wood is actually a natural polymers composite that is easy to process, mainly constituted of cellulose, hemicellulose and lignin. However, most wood-based functional materials are prepared by physical methods, which undoubtedly limit the application of wood-based materials. Herein, the wood aerogel (WA) was obtained from wood by delignification and freezing dried. The WA then was fabricated into an unexpected photochromic wood aerogel (PWA) via surface-initiated atom transfer radical polymerization (SI-ATRP) covalently grafting poly{6-[4-(4-methoxyphenyl-azo)phenoxy]hexyl methacrylate} (PMAZOM). Both WA and PWA showed good compression resilience. The hydrophobicity of PWA was obviously enhanced because of the surface modification. The color of PWA can change from yellow to orange-red after being irradiated by UV light for 30 s. The color of sample can be reversibly changed to yellow under sunlight for 200 s. The lightweight and photosensitive wood aerogel is potential to apply for optical information storage materials and photosensitive devices.

Nb2O5 synthesis and characterization by Pechini method to the application as electron transport material in a solar device

Renewable energy methodologies are the key to a sustainable future. PV technology has been raised as one of the most promisor alternatives for energy conversion, due to the use of an inexhaustible source. The third generation of solar devices, present in composition a semiconductor oxide, that work as electron transport material (ETL), receiving and transporting the electron from a photosensitive molecule. TiO2 performs with efficiency the role of ETL in solar devices, nevertheless, since of the higher cost, other oxides have been studied, as Nb2O5. This work aims to synthetized Nb2O5 by Pechini methodology and applied it as ETL in a solar device. The techniques performed in particle characterization were Scanning Electronic Microscopy (SEM) and X-ray diffraction (XRD). To verify the capability of transport electrons, the electrochemical measurements were applied to Voc/Jsc decay, j-V curves, Electrochemical Impedance Spectroscopy (EIS), and Intensity Modulate Photovoltage Spectroscopy (IMVS). The results showed Nb2O5 synthesized in orthorhombic phase able to produce a photosensitive dye-solar device with j = 4.18 mA cm−2, V = 825 mV, FF = 0.4, PCE = 1.38% with slow recombination rate when compare to TiO2 dye-solar cell. The IMVS and EIS technique present the same accuracy to electron lifetime determination which is confirmed by the t-test performed.

Chromatic distortions of the frequency-contrast characteristic in photosensitive devices with charge coupling with full depletion

Chromatic distortions of the frequency-contrast characteristic in photosensitive devices with charge coupling with full depletion

Growth of ZnO nanorods array on PCB for enhanced UV photosensors

Ultraviolet (UV) photosensitive device is fabricated using ZnO nanorods array on commercially available printed circuit board (PCB). Facile open aqueous solution deposition (OASD) method is used to deposit ZnO nanorods array in a trenched region between closely spaced Cu-electrodes. X-ray diffraction (XRD) patterns confirm the wurtzite phase of ZnO nanorods arrays and scanning electron microscopy (SEM) characterizes the multidimensional growth of ZnO nanorods across the trenched part of PCB. The current-voltage (I-V) characteristics of the device in dark is analogous to the back-to-back diode behaviour. However, the device exhibits an excellent photoresponsivity wherein the photocurrent value increases by two orders of magnitude at 2 V bias under the illumination ultraviolet (UV wavelength  ~ 254 nm) light source. The enhancement in photocurrent is mainly due to formation of multiple contacts between neighbouring grain-boundaries of the nanorods arrays extending to the Cu-electrodes. The prototype optoelectronic device displays almost four-times increment in the UV photocurrent at 5 V external bias potential.

Influence of intensity on copper phthalocyanine based organic phototransistors

High performance photosensing devices have been effectively produced utilizing copper phthalocyanine (CuPc) as an organic photoactive material. The opto-electrical effects of organic semiconductor (OSC) based phototransistors are concentrated in this work. The light affectability of the thin film is examined using UV–Visible spectrometer. The current–voltage (I-V) curves with and without illumination represent that the device is highly sensitive towards illumination. The effect of illumination on the opto-electrical properties of the devices has been also investigated with constant bias voltage. The mobility of the fabricated devices could be enlarged definitely after light illumination. The fabricated device shows p-channel working with greatest carrier mobility of 0.41 ± 0.02 cm2/Vs under illumination. It was found that enhanced responsivity and an improved detectivity could be accomplished in lower intensity. The maximum responsivity and detectivity obtained from these devices were 1.14 ± 0 0.01 A/W and 4.57 ± 0.02 × 1011 Jones with 5 mW/cm2 intensity at very small bias voltage. Both high responsivity and detectivity portrayed in this study firmly suggest that CuPc based phototransistors are a good candidate for upcoming photosensitive and optoelectronic device applications.

Enhancing the photodetection performance of MAPbI3 perovskite photodetectors by a dual functional interfacial layer for color imaging.

The color imaging capacity of recently developed perovskite photodetectors (PDs) has not been fully explored. In this Letter, we fabricate a CH3NH3PbI3 (MAPbI3) PD as a color imaging sensor mainly due to its almost flat spectral response in a full visible light region. To enhance the photodetection performance, we introduce a dual functional interfacial TiO2 layer by atomic layer deposition, reducing the dark current to 12 pA from 13 nA and improving the photocurrent to 1.87 µA from 20 nA, resulting in a ∼105 fold enhancement of the ON/OFF ratio. Since we obtained satisfactory color images, we believe that the MAPbI3 perovskite PD is an ideal photosensitive device for color imaging.