Enhancement Of Photoresponse Research Articles

Enhancement in Photo-Response of CuZnS Nanocrystals-Based Photodetector Using Asymmetric Work Function Electrodes

In this study, an efficient visible light photodetector has been fabricated by using heavy metal-free CuZnS Nanocrystals with average particle size of 13±1 nm. This nanocrystal has been synthesized by a microwave (MW) assisted synthesis technique that has an optical band gap of 1.7 eV with an absorbance range of 300 to 700 nm. This device has been fabricated in a photoconductor geometry with CuZnS/ZnO bilayer structure and asymmetric work-function lateral electrodes. The work-function difference between the electrodes gives a driven voltage between the electrodes, which allows faster collection of charge carriers from the device. As a consequence, a significant photocurrent is generated by the device even without any external bias. The self-biased (at 0 V) external quantum efficiency (EQE) of this device is ∼4 % (at 430 nm) whereas this value reaches ∼20 % under 2 V external bias. The device possesses the responsivity (Rλ) and detectivity (D) of 8.8 A/W and 3.8 x 1012 Jones at 320 nm respectively under 2 V external bias.

Photoresponse enhancement mechanism of CuInP2S6-based device by coupling piezo-phototronic effect and ferroelectric polarization and its application of architecture monitoring

With the arrival of the information society, multifunctional integrated devices based on two-dimensional (2D) materials are crucial for promoting advanced technology. However, the impact of coupling of various physical effects on their performance remains unexplored. Herein, the influence of coupling of piezoelectricity, photoexcitation and ferroelectricity within 2D ferroelectric CuInP2S6 (CIPS), that is, the piezo-phototronic effect and the bulk photovoltaic effect, on the device photoelectric performance have been investigated. Our experiments show that the piezo-phototronic effect can improve the photoelectric performance of the poled devices by 1.36 times, and ferroelectric polarization in turn increases the impact of the piezo-phototronic effect on the performance of the poled devices by 3.8 times. Systematically band diagram analysis reveals that this mutual enhancement mechanism can be attributed to the contribution of piezoelectric polarization charges and Cu+ ions movement to carrier migration, which was supported by Kelvin probe force microscope, STEM, and first-principles calculations. Furthermore, an architecture monitoring system based on a CIPS device was constructed to detect building tilt in real-time. Our work provides a paradigm for enhancing the photoelectric performance of 2D ferroelectrics and has profound significance in investigating multi-physics effects coupling mechanisms in a single material.

High performance of UV photodetectors by integration of plasmonic Ag nanoparticles on GaN

High-performance ultraviolet photodetectors have attracted much attention due to their various potential applications from household to universal. On basis of this, in this work, a high – performance and photoresponse enhancement UV photodetector based on Ag NPs/GaN heterojunction was demonstrated. By incorporating of Ag nanoparticles, light confinement determined by Ag nanostructure offers an effective approach to break through the limitation of the light-mater interaction within the photoactive layers of photodetector. Various size and elemental composition of Ag NPs are fabricated on GaN lead to significant enhancement of photocurrent in UV photodetector. Consequently, an outstanding photoresponsivity of 89 A/W, external quantum efficiency of 2.8 × 103% at low bias voltage of 0.3 V were achieved. The improve photo-response of the Ag NPs-decorated GaN-based photodetector is attributed to the simultaneous effect of strong plasmon absorption, increased injection of hot electrons into the conduction band of GaN. This study will open up the direction to fabricate the high-performance UV photodetector.

Impact of deposition temperature on persistent photoconductivity of SnO2 thin films deposited using spray pyrolysis technique suitable in optoelectronic synaptic devices

In this study, nanocrystalline tin oxide thin films that exhibited enhanced persistent photoconductivity (PPC) were prepared using spray pyrolysis technique. The effect of deposition temperature on different aspects of photoconductivity of these films were analysed using different characterization techniques. Raman analysis confirmed the tetragonal rutile structure of the films and also indicated their nanocrystalline nature, while XPS analysis verified the presence and oxidation states of tin and oxygen in the films. The films demonstrated UV sensing capability under above-bandgap illumination, generating electron-hole pairs and enhancing electrical conductivity. The deposition temperature of the film influenced their photocurrent characteristics, showcasing varied responses in terms of photosensitivity and photocurrent. Enhancement of photoresponse was observed with the increase in deposition temperatures of the samples. Notably, films deposited at 450 and 500 °C exhibited the more persistent photocurrent at the tested deposition temperatures. The surface defects, oxygen vacancies and grain boundaries played a significant role in sustaining PPC by ionizing vacancies and creating persistent carriers even after light exposure by trapping free carriers and impeding recombination. From the exponential fitting and extrapolation of the decay curves, the sample prepared at 450 °C was observed to be the most suitable film in application point of view for fabricating devices that make use of persistent photoconductivity. Overall, this work highlights the effectiveness of modulation of deposition temperature in influencing photoconductor parameters of spray pyrolyzed tin oxide films, offering potential applications in non-volatile memory, bionic optoelectronics, neuromorphic computing and bioelectronics.

Enhancement of photoresponse and photovoltaic properties in KBiFe2O5/BiFeO3 bilayer thin films

In this report, the performance of a new photovoltaic device configuration in which bilayer KBiFe2O5 (KBFO)/BiFeO3 (BFO) as absorber materials have been investigated and compared with the single active layer-based devices of BFO and KBFO. The obtained short-circuit current density of 58.81 μAcm−2, open-circuit voltage of 0.65 V, and power conversion efficiency of 0.014 % for the complete photovoltaic device glass/FTO/KBFO/BFO/Ag are comparatively higher than that of glass/FTO/BFO/Ag and glass/FTO/KBFO/Ag devices. It has been observed that the active bilayer KBFO/BFO shows switchable photoresponse with respect to positive and negative polarities. This work may offer the procedures for further optimizing the photo absorber layer, thereby improving the performances of multiferroic-based devices for ferroelectric photovoltaic applications.

Large area MoSe2 and MoSe2/Bi2Se3 films on sapphire (0001) for near-infrared photodetection

The fabrication of heterojunction-based photodetectors (PDs) is well known for the enhancement of PDs performances, tunable nature of photoconductivity, and broadband application. Herein, the PDs based on MoSe2 and MoSe2/Bi2Se3 heterojunction on sapphire (0001) substrates were deposited using a r.f. magnetron sputtering system. The high-resolution x-ray diffraction and Raman spectroscopy characterizations disclosed the growth of the 2-H phase of MoSe2 and the rhombohedral phase of Bi2Se3 thin films on sapphire (0001). The chemical and electronic states of deposited films were studied using x-ray photoelectron spectroscopy and revealed the stoichiometry growth of MoSe2. We have fabricated metal-semiconductor–metal type PD devices on MoSe2 and MoSe2/Bi2Se3 heterojunction and the photo-response measurements were performed at external voltages of 0.1–5 V under near-infrared (1064 nm) light illumination. The bare MoSe2 PD device shows positive photoconductivity behavior whereas MoSe2/Bi2Se3 heterojunction PD exhibits negative photoconductivity. It was found that the responsivity of MoSe2 and MoSe2/Bi2Se3 heterojunction PDs is ~ 1.39 A W−1 and ~ 5.7 A W−1, respectively. The enhancement of photoresponse of MoSe2/Bi2Se3 PD nearly four-fold compared to bare MoSe2 PD shows the importance of heterojunction structures for futuristics optoelectronic applications.

Excitation of hybrid modes in plasmonic nanoantennas coupled with GeSiSn/Si multiple quantum wells for the photoresponse enhancement in the short-wave infrared range

Hybrid structures represented by a plasmonic nanoantenna array located on the surface of GeSiSn/Si multiple quantum wells (MQWs) grown on a silicon-on-insulator (SOI) substrate by molecular-beam epitaxy were developed for applications in the short-wave infrared range. Using numerical modeling methods, the electromagnetic characteristics of metasurfaces based on aluminum nanoantennas located on the surface of GeSiSn/Si nanoheterostructures were studied. It is shown that the spectral and spatial overlap of localized plasmons in nanoantennas and waveguide modes in the semiconductor film leads to the formation of hybrid modes with a Fano-type resonance profile. The possibility of significant photoluminescence (PL) enhancement of GeSiSn/Si MQWs through the use of hybrid plasmonic structures is demonstrated. The PL enhancement reached to 250 % at the wavelength of 1.9 μm, coinciding with the maximum of the reflectance spectrum for the hybrid structure. Based on the hybrid system, represented by the plasmonic nanoantenna array on the top part of GeSiSn/Si MQWs, p-i-n photodiodes were fabricated. The photocurrent enhancement was approximately 7 times at wavelengths of 1.73 µm and 1.8 µm. The excitation of separately localized plasmons and waveguide modes is demonstrated, and their hybridization is also studied.

Anisotropic spin transport and photoresponse characteristics detected by tip movement in magnetic single-molecule junction

Orientation-dependent transport properties induced by anisotropic molecules are enticing in single-molecule junctions. Here, using the first-principles method, we theoretically investigate spin transport properties and photoresponse characteristics in trimesic acid magnetic single-molecule junctions with different molecular adsorption orientations and electrode contact sites. The transport calculations indicate that a single-molecule switch and a significant enhancement of spin transport and photoresponse can be achieved when the molecular adsorption orientation changes from planar geometry to upright geometry. The maximum spin polarization of current and photocurrent in upright molecular junctions exceeds 90%. Moreover, as the Ni tip electrode moves, the tunneling magnetoresistance of upright molecular junctions can be increased to 70%. The analysis of the spin-dependent PDOS elucidates that the spinterfaces between organic molecule and ferromagnetic electrodes are modulated by molecular adsorption orientation, where the molecule in upright molecular junctions yields higher spin polarization. Our theoretical work paves the way for designing spintronic devices and optoelectronic devices with anisotropic functionality base on anisotropic molecules.

Quaternary nanoparticle array antenna for graphene/silicon near-infrared detector

Infrared imaging chips are crucial for a broad range of military, medicine and biology applications. Although silicon detectors’ on-chip integration technology is matured, their low absorption in near-infrared light results in poor infrared photocurrent response. To increase the photodetector absorption efficiency, antenna-like metal nanoparticles have been widely adopted due to their plasmon resonance effects. Oligomer nanoparticles, including quaternary nanoparticles, exhibit plasmon resonance effects that localize and enhance the light field in a sub-wavelength range. Furthermore, they can interfere with each other to achieve Fano resonance and bound state in continuity, resulting in a stronger localization and enhancement of the electromagnetic field. In this study an array of gold quaternary nanoparticle oligomers is used as the antenna for a graphene/SOI (with 1 μm silicon) heterojunction near-infrared detector. Each oligomer consists of four gold squares, each with a size of 250 nm, forming two pairs of dipoles similar to the orbital hybridization of hydrogen atoms. This thus results in a multi-body coupling structure with bonding state and anti-bonding state. The antenna array parameters, such as the periodic constant, gap between nanoparticles, and angle (<i>θ</i>) between the oligomers, are meticulously adjusted. The optimized device is characterized by using photocurrent and photocurrent mapping, achieving a 2-fold enhancement in photoresponsivity with the maximum value at <i>θ</i> ~ 40°. Notably, a consistent dip in photocurrents is observed for different periods or gap arrays when the angle theta is 20°. The simulation is conducted by using finite-difference time-domain (FDTD), revealing the emergence of Fano-like resonance in the transmittance spectra of the array at approximately 850 nm. The interference caused by the strongly coupling system to the plane coupled leakage field and the nanoparticle plasmon mode results in the formation of a new discrete leakage mode, i.e. the Fano-like resonance. The antenna helps to concentrate and emit the light field energy directionally to the detector, while there is a trade-off between the loss caused by nanoparticles absorption and the leakage energy. The photocurrent reaches a minimal point at a theta angle of 20° angle. At this point, the energy is localized in the oligomers, and the metal absorption loss weakens the plasmon enhancement effect. These findings are further supported by the simulation results of electric field and Poynting vector distribution. These findings indicate an important and promising way to enhance the photo detection efficiency via nanostructured plasmonic antenna.

Geometrically twisted intra-inter-molecular cooperative interactions for an enhanced photo-response in an ORMOSIL-based host-guest system.

In situ encapsulation of the 2-(2'-hydroxylphenyl)benzothiazole (HBT) fluorophore into organically modified silica (ORMOSIL) is recognized as a potential approach to increase the photocurrent conversion efficiency. Encapsulation resulted in a twisted geometrical configuration of HBT with an efficient charge transfer and increased carrier density, resulting in a 246% photo-response enhancement.

Ultraclean surface restoration and giant photoresponse enhancement of violet phosphorus

Violet phosphorus (VP), a recently developed kind of layered material, features exotic in-plane anisotropy, alluring thickness-dependent bandgap, and better thermal stability than its phosphorus allotropes. Such a broad variety of functionalities indicates VP is a promising candidate for advanced nanophotonics. However, its hydrophilic surface-induced air instability hinders further exploration and extensive device integration for photodetection and beyond. Herein, we report the successful restoration of the clean VP surfaces through nitrogen plasma combined with vacuum thermal annealing. Via manipulation of plasma excitation power, we can also achieve thickness etching and nondestructive p-doping to VP, paving the way for fabrication and engineering of VP photodetectors. As a proof-of-concept, plasma-treated VP photodetectors have been fabricated. Stemming from the plasma treatment-induced p-doping and hole trapping centers, the VP photodetectors exhibit giant photoresponse enhancement, reaching a high responsivity of 1.923 A/W, and is dramatically improved by 1300% compared with that before plasma treatments, which envisions high-sensitivity photodetection for next-generation more-than-Moore optoelectronics.

Impact of Solid-State Charge Injection on Spectral Photoresponse of NiO/Ga2O3 p–n Heterojunction

Forward bias hole injection from 10-nm-thick p-type nickel oxide layers into 10-μm-thick n-type gallium oxide in a vertical NiO/Ga2O3 p–n heterojunction leads to enhancement of photoresponse of more than a factor of 2 when measured from this junction. While it takes only 600 s to obtain such a pronounced increase in photoresponse, it persists for hours, indicating the feasibility of photovoltaic device performance control. The effect is ascribed to a charge injection-induced increase in minority carrier (hole) diffusion length (resulting in improved collection of photogenerated non-equilibrium carriers) in n-type β-Ga2O3 epitaxial layers due to trapping of injected charge (holes) on deep meta-stable levels in the material and the subsequent blocking of non-equilibrium carrier recombination through these levels. Suppressed recombination leads to increased non-equilibrium carrier lifetime, in turn determining a longer diffusion length and being the root-cause of the effect of charge injection.

Unraveling the Role of Liquid Metal Catalysts in Electrochemical Growth of Solar Si from SiO2 in CaCl2-Based Molten Salt: Enhancement of Crystallization, Purity, and Photoresponse

Unraveling the Role of Liquid Metal Catalysts in Electrochemical Growth of Solar Si from SiO₂ in CaCl₂-Based Molten Salt: Enhancement of Crystallization, Purity, and Photoresponse

Fabrication and Enhancement of Organic Photodetectors Based on Iron Phthalocyanine Films

Iron–phthalocyanine (FePc) organic photoconductive detector was fabricated using pulsed laser deposition (PLD) technique to work in ultraviolet (UV) and visible regions. The organic semiconductor material (iron phthalocyanine) was deposited on n-type silicon wafer (Si) substrates at different thicknesses (100, 200 and 300) nm. FePc organic photoconductive detector has been improved by two methods: the first is to manufacture the detector on PSi substrates, and the second is by coating the detector with polyamide–nylon polymer to enhance the photoconductivity of the FePc detector. The current–voltage (I–V) characteristics, responsivity, photocurrent gain, response time and the quantum efficiency of the fabricated photoconductive detector were measured. The performance of the fabricated detector was taken under dark and illumination using two types of light sources: UV LED with wavelength (365[Formula: see text]nm), power of (10[Formula: see text]W) and Tungsten lamp with wavelength range between (500–800) nm and the optical power of (250[Formula: see text]W). The photoresponse enhancement was improved by coating the FePc films with 200[Formula: see text]nm of polyamide nylon polymer. This type of coating, which can be considered as a surface treatment, highly increased the photoresponse of the fabricated FePc UV detector. The results show that the responsivity increased four orders of magnitudes more than the responsivity of the uncoated FePc film. The effects of the coated polymers on the responsivity and the response time of the detector were investigated.

Visible light driven CZTS QDs/α-Fe2O3-graphene p–n heterojunction for photoelectrochemical water splitting

This work investigates the implication of graphene and Cu2ZnSnS4 (CZTS) quantum dots (QDs) incorporation in the hematite thin film for its use in a photoelectrochemical cell. The thin film has been prepared by decorating the CZTS QDs over graphene-hematite composite by simple chemical approach. In Comparison to graphene modification and CZTS QDs modification separately over hematite thin film, the combination of both has produced more photocurrent. The photocurrent density obtained for CZTS QDs and graphene modified hematite thin film is 1.82 mA cm−2 at 1.23 V/RHE, which is 1.75 higher than pristine hematite. The presence of CZTS QDs over hematite-graphene composite enhances the absorption properties of composite along with creating the p–n junction heterostructure which aids the transportation of the charge carriers. The thin films have been characterized using x-ray diffractometer, Raman spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy, and diffuse reflectance UV–vis spectroscopy for phase, morphology and optical properties analysis. The enhancement in photoresponse has been justified by Mott-Schottky and transient open circuit potential analysis.

Remarkable enhancement of photoluminescence and photoresponse due to photonic crystal structures based on GeSiSn/Si multiple quantum wells

The GeSiSn/Si structures surface with multiple quantum wells (MQWs) was modified by developing photonic crystals (PCs) to increase the photoluminescence and photoresponse near 2 μm. The structural parameters of GeSiSn/Si MQWs obtained by molecular-beam epitaxy were optimized, and PCs were formed. They consisted of a periodic cylindrical hole array. Numerical simulation methods were used to optimize the hole depth, which makes it possible to effectively excite quasi-guided modes and not affect the active layer including GeSiSn/Si MQWs. The increase of the photoluminescence (PL) signal related to vacancy complexes was observed for all samples with the PC structure. The maximum PL amplification of about 5 times at the wavelength near 2 μm was demonstrated. The annealing of PC structures with GeSiSn/Si MQWs resulted in the appearance of PL associated with interband optical transitions. The PL enhancement was observed by almost an order of magnitude in the narrow wavelength range with the PL maximum near 1.8 μm. Based on Ge0.84Si0·076Sn0·084/Si MQWs p-i-n photodiodes with the PC, the photoresponse increase was shown in the wide wavelength range up to 1.8 μm.

Self-powered white light photodetector with enhanced photoresponse using camphor sulphonic acid treated CsPbBr3 perovskite in carbon matrix

The surface modification of CsPbBr3 perovskite provides an effective way of defect passivation for device applications. In this work, Camphor sulfonic acid (CSA) was used to modify the surface of CsPbBr3 microcrystals (MCs) and helped in enhancement of Photoluminescence (PL) emission, photoresponse, and photodetectivity. We fabricated the perovskite FTO/c-TiO2/CsPbBr3-CSA/Carbon composite self-powered photodetector. The device exhibited higher photo responsivity and detectivity of 1.523 mA/W and 2.1454 × 109 Jones, respectively, under white light with excellent stability on high ON/OFF cycles.

ZnO UV sensor photoresponse enhancement by coating method optimization

Modern high-performance photodetector research is driven by the need to simultaneously improve multiple parameters, but also fit the decreasing size of electronics and maintain low production price. Here, we demonstrated how our synthesized ZnO tetrapod (ZnO-T) nanostructure was deposited on electrodes with variating gap by four coating methods including drop casting, microdrop casting, spray coating and slot-die coating with the same thickness. Optimizing the inter-electrode gap and coating method the record IUV/IDark ratio per unit area value of 8.73 × 106 was obtained. The fastest rise time 0.78 s and fastest decay time 0.94 s were obtained by slot-die coated sensors. High photoresponse of ZnO-Ts, the inter-electrode gap size influences formation of ZnO-T microstructure during coating process and morphology influence on photoresponse was explained. We demonstrate that even with the same optimized ZnO-T nanostructures photoresponse can be improved by 2 orders of magnitude. Our work shows the importance of coating morphology and inter-electrode gap optimization.

Enhancement in photo response of spray deposited Yttrium doped Bi2S3 thin films

Enhancement in photo response of spray deposited Yttrium doped Bi2S3 thin films

An infrared photothermoelectric detector enabled by MXene and PEDOT:PSS composite for noncontact fingertip tracking

Photothermoelectric (PTE) detectors functioning on the infrared spectrum show much potential for use in many fields, such as energy harvesting, nondestructive monitoring, and imaging fields. Recent advances in low-dimensional and semiconductor materials research have facilitated new opportunities for PTE detectors to be applied in material and structural design. However, these materials applied in PTE detectors face some challenges, such as unstable properties, high infrared reflection, and miniaturization issues. Herein, we report our fabrication of scalable bias-free PTE detectors based on Ti3C2 and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) composites and characterization of their composite morphology and broadband photoresponse. We also discuss various PTE engineering strategies, including substrate choices, electrode types, deposition methods, and vacuum conditions. Furthermore, we simulate metamaterials using different materials and hole sizes and fabricated a gold metamaterial with a bottom-up configuration by simultaneously combining MXene and polymer, which achieved an infrared photoresponse enhancement. Finally, we demonstrate a fingertip gesture response using the metamaterial-integrated PTE detector. This research proposes numerous implications of MXene and its related composites for wearable devices and Internet of Things (IoT) applications, such as the continuous biomedical tracking of human health conditions.