In this work,we studied the persistent photoconductivity(PPC)spectra in single HgTe/CdHgTe quantum wells with different growth parameters and different types of dark conductivity.The studies were performed in a wide r...In this work,we studied the persistent photoconductivity(PPC)spectra in single HgTe/CdHgTe quantum wells with different growth parameters and different types of dark conductivity.The studies were performed in a wide radiation quantum energy range of 0.62–3.1 eV both at T=4.2 K and at T=77 K.Common features of the PPC spectra for all structures were revealed,and their relation to the presence of a CdTe cap layer in all structures and the appropriate cadmium fraction in the CdHgTe barrier layers was shown.One of the features was associated with the presence of a deep level in the CdTe layer.In addition,the oscillatory behavior of the PPC spectra in the region from 0.8–1.1 eV to 1.2–1.5 eV was observed.It is associated with the cascade emission of longitudinal optical phonons in CdHgTe barrier.展开更多
Light induced changes in a-Si∶H films are investigated by transient photoconductivity.The transient photoconductivity decay data can neither be fit well by common power-law for transient photocurrent in amorphous sem...Light induced changes in a-Si∶H films are investigated by transient photoconductivity.The transient photoconductivity decay data can neither be fit well by common power-law for transient photocurrent in amorphous semiconductors,nor by stretched exponential rule for transient decay from the steady state in photoconductivity.Instead,the data are fit fairly well with a sum of two exponential functions.The results show that the long time decay is governed by deep traps rather than band tail states,and two different traps locating separately at 0.52 and 0.59eV below E _c are responsible for the two exponential functions.They are designated as negatively charged dangling bond D - centers.The light-induced changes in photoconductivity are attributed mainly to the decrease in electron lifetime caused by the increase of recombination centers after light soaking.展开更多
Photocatalysis shows great promise in the field of solar energy conversion.One of the reasons for this is because it promotes the development of multi-field-coupled catalysis.In order to explore the principles of mult...Photocatalysis shows great promise in the field of solar energy conversion.One of the reasons for this is because it promotes the development of multi-field-coupled catalysis.In order to explore the principles of multi-field-coupled catalytic reactions,an in situ multi-field-coupled characterization technique is required.In this study,we obtained hydrogenated ST-01 TiO2 and observed enhanced catalytic activity by thermal coupled photocatalysis.In situ photoconductivity was employed to understand the activity enhancement.The effects of the reaction temperature,reaction atmosphere,and oxygen vacancy(Ov)on the photoconductivity of TiO2 were studied.After coupling thermal into photoconductivity measurement,highly active Ov-TiO2 displayed rapid decay of photoconductivity in a CO2 atmosphere and slow decay of photoconductivity in a N2 atmosphere.These phenomena revealed that photothermal coupling assisted the detrapping of electrons at the Ov surface and promoted electron transfer to CO2,which clearly explained the high photothermal catalytic activity of Ov-TiO2.This study demonstrated that photoconductivity is a useful tool to help understand photothermal catalytic phenomena.展开更多
In recent years,low-dimensional materials have received extensive attention in the field of electronics and optoelectronics.Among them,photoelectric devices based on photoconductive effect in low-dimensional materials...In recent years,low-dimensional materials have received extensive attention in the field of electronics and optoelectronics.Among them,photoelectric devices based on photoconductive effect in low-dimensional materials have a broad development space.In contrast to positive photoconductivity,negative photoconductivity(NPC)refers to a phenomenon that the conductivity decreases under illumination.It has novel application prospects in the field of optoelectronics,memory,and gas detection,etc.In this paper,we review reports about the NPC effect in low-dimensional materials and systematically summarize the mechanisms to form the NPC effect in existing low-dimensional materials.展开更多
The present work describes the effect of deposition potentials on structural,morphological,optical,electrical and photoconductivity responses of cuprous oxide(Cu2O)thin films deposited on fluorine-doped tin oxide glas...The present work describes the effect of deposition potentials on structural,morphological,optical,electrical and photoconductivity responses of cuprous oxide(Cu2O)thin films deposited on fluorine-doped tin oxide glass substrate by employing electrodeposition technique.X-ray diffraction patterns reveal that the deposited films have a cubic structure grown along the preferential(111)growth orientation and crystallinity of the film deposited at.0.4 V is improved compared to the films deposited at.0.2,.0.3 and.0.5 V.Scanning electron microscopy displays that surface morphology of Cu2O film has a well-defined three-sided pyramid-shaped grains which are uniformly distributed over the surface of the substrates and are significantly changed as a function of deposition potential.Raman and photoluminescence spectra manifest that the film deposited at.0.4 V has a good crystal quality with higher acceptor concentration compared to other films.UV–visible analysis illustrates that the absorption of Cu2O thin film deposited at.0.4 V is notably higher compared to other films and the band gap of Cu2O thin films decreases from 2.1 to 2.04 eV with an increase in deposition potential from.0.2 to.0.5 V.The frequency–temperature dependence of impedance analysis shows that the film deposited at.0.4 V has a high conductivity.I– V measurements elucidate that the film deposited at.0.4 V exhibits a good photoconductivity response compared to films deposited in other deposition potentials.展开更多
The paper reported a theoretical study on the photoconductivity of a bifacial silicon solar cell under polychromatic illumination and a constant magnetic field effect. By use of the continuity equation in the base of ...The paper reported a theoretical study on the photoconductivity of a bifacial silicon solar cell under polychromatic illumination and a constant magnetic field effect. By use of the continuity equation in the base of the solar cell maintained in a constant temperature at 300 K, an expression of the excess minority carriers’ density was determined according to the applied magnetic field, the base depth and the junction recombination velocity. From the expression of the minority carriers’ density, the photoconductivity of the solar cell was deduced and which allowed us to predict some recombination phenomena, the use of such solar cell in optoelectronics. The profile of the photoconductivity also permitted us to utilize a linear model in order to determine an electrical capacitance that varied with magnetic field.展开更多
Using time-dependent terahertz spectroscopy, we investigate the role of mixed-cation and mixed-halide on the ultrafast photoconductivity dynamics of two different methylammonium(MA) lead-iodide perovskite thin films. ...Using time-dependent terahertz spectroscopy, we investigate the role of mixed-cation and mixed-halide on the ultrafast photoconductivity dynamics of two different methylammonium(MA) lead-iodide perovskite thin films. It is found that the dynamics of conductivity after photoexcitation reveals significant correlation on the microscopy crystalline features of the samples. Our results show that mixed-cation and lead mixed-halide affect the charge carrier dynamics of the lead-iodide perovskites. In the(5-AVA)_(0.05)(MA)_(0.95) PbI_(2.95) Cl_(0.05)/spiro thin film, we observe a much weaker saturation trend of the initial photoconductivity with high excitation fluence, which is attributed to the combined effect of sequential charge carrier generation, transfer, cooling and polaron formation.展开更多
Functional phthalocyanine （Pc） compounds of H2Pc, TiOPc, FePc and CIAIPc were synthesized with a yield of 46.7%, 91.2%, 37.4% and 34.0%, respectively. Nanosized TiOPc was synthesized via a one-step sol-gel method an...Functional phthalocyanine （Pc） compounds of H2Pc, TiOPc, FePc and CIAIPc were synthesized with a yield of 46.7%, 91.2%, 37.4% and 34.0%, respectively. Nanosized TiOPc was synthesized via a one-step sol-gel method and effects of surfactant doses, nucleation temperature on TiOPc particle size and photoconductivity were investigated. When re（PEG）： m（TiOPc） was 0.1 and nucleation temperature was 0℃, the as-obtained TiOPc had the smallest particle size and largest specific surface area, which were 60 nm and 83m^2/g, respectively. TiOPc synthesized under these conditions also exhibits excellent photoconductivity with charging potential V0, dark decay speed Rd and energy for half-discharging of potential E1/2 being 1160 V, 30 V/s and 0.6 1x.s, respectively.展开更多
Fe (III) 2,9,16,23 tertracarboxy phthalocyanine (Fe (III) taPc) was synthesized, and bonded to polystyrene (PS) with covalence by Friedel Crafts reaction to form a new polymer (Fe (III) taPc PS) (polymer (II))....Fe (III) 2,9,16,23 tertracarboxy phthalocyanine (Fe (III) taPc) was synthesized, and bonded to polystyrene (PS) with covalence by Friedel Crafts reaction to form a new polymer (Fe (III) taPc PS) (polymer (II)). UV VIS and Infrared spectra indicated that Fe (III) taPc was successfully bonded to PS. A photoreceptor device of sandwich structure consisting of alternate layers of polymer (II) and fullerene (C 60 ) was prepared. The experiment results show that the photoconductivity of the photoreceptor is higher than that of the single layer film of polymer (II) or C 60 , because of the charge transfer effect between the layers.展开更多
The utilization of processing capabilities within the detector holds significant promise in addressing energy consumption and latency challenges. Especially in the context of dynamic motion recognition tasks, where su...The utilization of processing capabilities within the detector holds significant promise in addressing energy consumption and latency challenges. Especially in the context of dynamic motion recognition tasks, where substantial data transfers are necessitated by the generation of extensive information and the need for frame-by-frame analysis. Herein, we present a novel approach for dynamic motion recognition, leveraging a spatial-temporal in-sensor computing system rooted in multiframe integration by employing photodetector. Our approach introduced a retinomorphic MoS_(2) photodetector device for motion detection and analysis. The device enables the generation of informative final states, nonlinearly embedding both past and present frames. Subsequent multiply-accumulate (MAC) calculations are efficiently performed as the classifier. When evaluating our devices for target detection and direction classification, we achieved an impressive recognition accuracy of 93.5%. By eliminating the need for frame-by-frame analysis, our system not only achieves high precision but also facilitates energy-efficient in-sensor computing.展开更多
The donor-acceptor complex HEC-TCNQ (HEC = 9-hydroxyethylcarbazole; TCNQ = tetracyanoquinodimethane) has been synthesized. Under the illumination of Ar+ laser, the photoinduced charge transfer salt HEC(+)TCNQ(-) can b...The donor-acceptor complex HEC-TCNQ (HEC = 9-hydroxyethylcarbazole; TCNQ = tetracyanoquinodimethane) has been synthesized. Under the illumination of Ar+ laser, the photoinduced charge transfer salt HEC(+)TCNQ(-) can be formed with a conductivity of at least one order of magnitude larger than that of HEC-TCNQ.展开更多
LaAlO_(3)/SrTiO_(3)(LAO/STO)heterostructures have shown a strong persistent photoconductivity(PPC)at room temperature.The abnormally strong PPC has attracted immense research interest due to its possible applications ...LaAlO_(3)/SrTiO_(3)(LAO/STO)heterostructures have shown a strong persistent photoconductivity(PPC)at room temperature.The abnormally strong PPC has attracted immense research interest due to its possible applications in optically-tunable electronic devices.Despite its promise,the fundamental understanding of the PPC in the LAO/STO heterostructures is still elusive.Herein,we report that the giant PPC origi-nates from the photo-induced valence change in oxygen vacancies near the LAO/STO interface.Our spec-tral analysis of the photocurrent and the model-fitting study consistently show that the ionized oxygen vacancies near the interface are neutralized during the electron relaxation process.They hinder the complete relaxation of the photoexcited electrons by the deeply-located oxygen vacancies and result in the strong PPC.The change in the ionization state distribution of the oxygen vacancies is probed by the per-sistent noise behavior at the frequency between 1 kHz and 20 kHz regime.These results provide insight into the role of oxygen vacancies in influencing the internal charge distribution and triggering the PPC phenomena in complex oxide heterostructures.展开更多
The photoconductivities of a series of novel polyacetylene derivatives （PAs） serving as charge generation materials in the single-layered photoreceptors were investigated using photoinduced xerographic discharge tec...The photoconductivities of a series of novel polyacetylene derivatives （PAs） serving as charge generation materials in the single-layered photoreceptors were investigated using photoinduced xerographic discharge technique. It was found that the substitution can improve the photosensitivity of PAs by increasing the conjugation of π electrons. When the substituent is itself photoconductive, the photoconductivity becomes even higher. It can be concluded from cyclic voltammetry that when the HOMO level of the polymer is closer to that of the charge transport material, the photoconduction performance will be better.展开更多
Size-controllable and vertically-oriented TiO2 nanotube(TNT)arrays were fabricated using anodic oxidation method from pure titanium sheets in electrolyte solutions.Then with the TNT arrays as the working electrode,a t...Size-controllable and vertically-oriented TiO2 nanotube(TNT)arrays were fabricated using anodic oxidation method from pure titanium sheets in electrolyte solutions.Then with the TNT arrays as the working electrode,a thin film of polypyrrole(Ppy)was synthesized into the TNT arrays via the electrochemical polymerization.During the process,the appearance of redox peaks in cyclic voltammetry curves of the resulting films indicates the occurrence of polymerization.The morphology,the molecular structure, crystallization and optical properties of the TNT arrays and the resulting polymer were investigated by field-emission scanning electron microscopy(FESEM),X-ray diffractometry(XRD),Fourier transform infrared spectroscopy(FTIR),and UV-vis spectrum analysis,respectively.A dual-layered photoreceptor containing the nanocomposite film as the charge generation layer(CGL)was designed and fabricated.It is found that the photoreceptor based on Ppy/TiO2 nanotubes as CGL exhibits remarkable photoconductive performance.展开更多
Persistent photoconductivity(PPC)effect and its light-intensity dependence of both enhancement and depletion(E-/D-)mode amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs)are systematically investigated.Density of ox...Persistent photoconductivity(PPC)effect and its light-intensity dependence of both enhancement and depletion(E-/D-)mode amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs)are systematically investigated.Density of oxygen vacancy(V O)defects of E-mode TFTs is relatively small,in which formation of the photo-induced metastable defects is thermally activated,and the activation energy(E a)decreases continuously with increasing light-intensity.Density of V O defects of D-mode TFTs is much larger,in which the formation of photo-induced metastable defects is found to be spontaneous instead of thermally activated.Furthermore,for the first time it is found that a threshold dose of light-exposure is required to form fully developed photo-induced metastable defects.Under low light-exposure below the threshold,only a low PPC barrier is formed and the PPC recovery is fast.With increasing the light-exposure to the threshold,the lattice relaxation of metal cations adjacent to the doubly ionized oxygen vacancies(V O^2+)is fully developed,and the PPC barrier increases to∼0.25 eV,which remains basically unchanged under higher light-exposure.Based on the density of V O defects in the channel and the condition of light illumination,a unified model of formation of photo-induced metastable defects in a-IGZO TFTs is proposed to explain the experimental observations.展开更多
An in-depth understanding of the photoconductivity and photocarrier density at the interface is of great significance for improving the performance of optoelectronic devices. However, extraction of the photoconductivi...An in-depth understanding of the photoconductivity and photocarrier density at the interface is of great significance for improving the performance of optoelectronic devices. However, extraction of the photoconductivity and photocarrier density at the heterojunction interface remains elusive. Herein, we have obtained the photoconductivity and photocarrier density of 173 nm Sb2Se3/Si(type-Ⅰ heterojunction) and 90 nm Sb2Se3/Si(type-Ⅱ heterojunction) utilizing terahertz(THz) time-domain spectroscopy(THz-TDS) and a theoretical Drude model. Since type-Ⅰ heterojunctions accelerate carrier recombination and type-Ⅱ heterojunctions accelerate carrier separation, the photoconductivity and photocarrier density of the type-Ⅱ heterojunction(21.8×10^(4)S·m^(-1),1.5 × 10^(15)cm^(-3)) are higher than those of the type-Ⅰ heterojunction(11.8×10^(4)S·m^(-1),0.8×10^(15)cm^(-3)). These results demonstrate that a type-Ⅱ heterojunction is superior to a type-Ⅰ heterojunction for THz wave modulation. This work highlights THz-TDS as an effective tool for studying photoconductivity and photocarrier density at the heterojunction interface. In turn, the intriguing interfacial photoconductivity effect provides a way to improve the THz wave modulation performance.展开更多
This paper investigates the ultrafast carrier dynamics and surface photoconductivity of unbiased semi-insulating GaAs in detail by using a terahertz pump-emission technique. Based on theoretical modelling, it finds th...This paper investigates the ultrafast carrier dynamics and surface photoconductivity of unbiased semi-insulating GaAs in detail by using a terahertz pump-emission technique. Based on theoretical modelling, it finds that transient photoconductivity plays a very important role in the temporal waveform of terahertz radiation pulse. Anomalous enhancement in both terahertz radiation and transient photoconductivity is observed after the excitation of pump pulse and we attribute these phenomena to carrier capture in the EL2 centers. Moreover, the pump power- and temperature- dependent measurements are also performed to verify this trapping model.展开更多
The defect-related photoconductivity gain and persistent photoconductivity(PPC)observed in Ga_(2)O_(3)Schottky photodetectors lead to a contradiction between high responsivity and fast recovery speed.In this work,a me...The defect-related photoconductivity gain and persistent photoconductivity(PPC)observed in Ga_(2)O_(3)Schottky photodetectors lead to a contradiction between high responsivity and fast recovery speed.In this work,a metal-semiconductor-metal(MSM)Schottky photodetector,a unidirectional Schottky photodetector,and a photoconductor were constructed on Ga_(2)O_(3)films.The MSM Schottky devices have high gain(>13)and high responsivity(>2.5 A/W)at 230-250 nm,as well as slow recovery speed caused by PPC.Interestingly,applying a positive pulse voltage to the reverse-biased Ga_(2)O_(3)/Au Schottky junction can effectively suppress the PPC in the photodetector,while maintaining high gain.The mechanisms of gain and PPC do not strictly follow the interface trap trapping holes or the self-trapped holes models,which is attributed to the correlation with ionized oxygen vacancies in the Schottky junction.The positive pulse voltage modulates the width of the Schottky junction to help quickly neutralize electrons and ionized oxygen vacancies.The realization of suppression PPC functions and the establishment of physical models will facilitate the realization of high responsivity and fast response Schottky devices.展开更多
Persistent photoconductivity has been investigated by various models, among which the Macroscopic Barrier model, Large-Lattice-Relaxation model, and Random Local Potential Fluctuations model are mostly well known. Alt...Persistent photoconductivity has been investigated by various models, among which the Macroscopic Barrier model, Large-Lattice-Relaxation model, and Random Local Potential Fluctuations model are mostly well known. Although the three well-known models have played important roles in describing the persistent photoconductivity, they are not the principal cause of persistent photoconductivity. In this paper a classical model originated from ＂selfmagnetism of electron gas＂ is proposed to illustrate the persistent photoconductivity phenomenon. This classical model is based on electron gas pulsation, which depends on the charge density. Different concentrations of current carriers create different frequencies in the system, and thus the system is sensitive to different wave lengths of incident light. Then the construction of different detectors can be possible for different wave lengths of incident light.展开更多
It is essential to determine the accumulative ultraviolet(UV)irradiation over a period of time in some cases,such as monitoring UV irradiation to the skin,solar disinfection of water,photoresist exposure,etc.UV colori...It is essential to determine the accumulative ultraviolet(UV)irradiation over a period of time in some cases,such as monitoring UV irradiation to the skin,solar disinfection of water,photoresist exposure,etc.UV colorimetric dosimeters,which use dyes'color change to monitor the amount of UV exposure,have been widely studied.However,the exposure data of these UV colorimetric dosimeters can hardly be converted to digital signals,limiting their applications.In this paper,a UV dosimeter has been proposed and demonstrated based on the persistent photoconductivity(PPC)in zinc oxide microwires(ZnO MWs).The PPC effect usually results in high photoconductivity gain but low response speed,which has been regarded as a disadvantage for photodetectors.However,in this work,the unique characteristics of the PPC effect have been utilized to monitoring the accumulative exposure.We demonstrate that the photocurrent in the ZnO MWs depends on the accumulative UV exposure due to the PPC effect,thus the photocurrent can be utilized to determine the UV accumulation.The dosimeter is immune to visible light and exhibits a photoconductive gain of 2654,and the relative error of the dosimeter is about 10%.This UV dosimeter with electrical output is reusable and convenient to integrate with other electronic devices and may also open a new application area for the PPC effect.展开更多
基金supported by the Russian Science Foundation (Grant No. 22-12-00298)supported by the Center of Excellence "Center of Photonics" funded by the Ministry of Science and Higher Education of the Russian Federation, Contract #075-15-2022-316the Theoretical Physics and Mathematics Advancement Foundation "BASIS" scholarship for the support.
文摘In this work,we studied the persistent photoconductivity(PPC)spectra in single HgTe/CdHgTe quantum wells with different growth parameters and different types of dark conductivity.The studies were performed in a wide radiation quantum energy range of 0.62–3.1 eV both at T=4.2 K and at T=77 K.Common features of the PPC spectra for all structures were revealed,and their relation to the presence of a CdTe cap layer in all structures and the appropriate cadmium fraction in the CdHgTe barrier layers was shown.One of the features was associated with the presence of a deep level in the CdTe layer.In addition,the oscillatory behavior of the PPC spectra in the region from 0.8–1.1 eV to 1.2–1.5 eV was observed.It is associated with the cascade emission of longitudinal optical phonons in CdHgTe barrier.
文摘Light induced changes in a-Si∶H films are investigated by transient photoconductivity.The transient photoconductivity decay data can neither be fit well by common power-law for transient photocurrent in amorphous semiconductors,nor by stretched exponential rule for transient decay from the steady state in photoconductivity.Instead,the data are fit fairly well with a sum of two exponential functions.The results show that the long time decay is governed by deep traps rather than band tail states,and two different traps locating separately at 0.52 and 0.59eV below E _c are responsible for the two exponential functions.They are designated as negatively charged dangling bond D - centers.The light-induced changes in photoconductivity are attributed mainly to the decrease in electron lifetime caused by the increase of recombination centers after light soaking.
基金supported by the Natural Science Foundation of China(51072032,51372036,51102001)the Key Project of Chinese Ministry of Education(113020A)+1 种基金the 111 project(B13013)Jilin Province Science and Technology Development Plan(20180101175JC,20160520170JH)~~
文摘Photocatalysis shows great promise in the field of solar energy conversion.One of the reasons for this is because it promotes the development of multi-field-coupled catalysis.In order to explore the principles of multi-field-coupled catalytic reactions,an in situ multi-field-coupled characterization technique is required.In this study,we obtained hydrogenated ST-01 TiO2 and observed enhanced catalytic activity by thermal coupled photocatalysis.In situ photoconductivity was employed to understand the activity enhancement.The effects of the reaction temperature,reaction atmosphere,and oxygen vacancy(Ov)on the photoconductivity of TiO2 were studied.After coupling thermal into photoconductivity measurement,highly active Ov-TiO2 displayed rapid decay of photoconductivity in a CO2 atmosphere and slow decay of photoconductivity in a N2 atmosphere.These phenomena revealed that photothermal coupling assisted the detrapping of electrons at the Ov surface and promoted electron transfer to CO2,which clearly explained the high photothermal catalytic activity of Ov-TiO2.This study demonstrated that photoconductivity is a useful tool to help understand photothermal catalytic phenomena.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61574011 and 51761145025)the Key Program of the National Natural Science Foundation of China(Grant No.No.61731019)the Natural Science Foundation of Beijing,China(Grant Nos.4182015 and 4182014)。
文摘In recent years,low-dimensional materials have received extensive attention in the field of electronics and optoelectronics.Among them,photoelectric devices based on photoconductive effect in low-dimensional materials have a broad development space.In contrast to positive photoconductivity,negative photoconductivity(NPC)refers to a phenomenon that the conductivity decreases under illumination.It has novel application prospects in the field of optoelectronics,memory,and gas detection,etc.In this paper,we review reports about the NPC effect in low-dimensional materials and systematically summarize the mechanisms to form the NPC effect in existing low-dimensional materials.
基金the funding and support from the RUSA-Phase 2.0 grant sanctioned vide Letter. No. F. 24-51/2014-U, Policy (TNMulti-Gen), Dept. of Edn. Govt. of India. Dt. 09.10.2018.
文摘The present work describes the effect of deposition potentials on structural,morphological,optical,electrical and photoconductivity responses of cuprous oxide(Cu2O)thin films deposited on fluorine-doped tin oxide glass substrate by employing electrodeposition technique.X-ray diffraction patterns reveal that the deposited films have a cubic structure grown along the preferential(111)growth orientation and crystallinity of the film deposited at.0.4 V is improved compared to the films deposited at.0.2,.0.3 and.0.5 V.Scanning electron microscopy displays that surface morphology of Cu2O film has a well-defined three-sided pyramid-shaped grains which are uniformly distributed over the surface of the substrates and are significantly changed as a function of deposition potential.Raman and photoluminescence spectra manifest that the film deposited at.0.4 V has a good crystal quality with higher acceptor concentration compared to other films.UV–visible analysis illustrates that the absorption of Cu2O thin film deposited at.0.4 V is notably higher compared to other films and the band gap of Cu2O thin films decreases from 2.1 to 2.04 eV with an increase in deposition potential from.0.2 to.0.5 V.The frequency–temperature dependence of impedance analysis shows that the film deposited at.0.4 V has a high conductivity.I– V measurements elucidate that the film deposited at.0.4 V exhibits a good photoconductivity response compared to films deposited in other deposition potentials.
文摘The paper reported a theoretical study on the photoconductivity of a bifacial silicon solar cell under polychromatic illumination and a constant magnetic field effect. By use of the continuity equation in the base of the solar cell maintained in a constant temperature at 300 K, an expression of the excess minority carriers’ density was determined according to the applied magnetic field, the base depth and the junction recombination velocity. From the expression of the minority carriers’ density, the photoconductivity of the solar cell was deduced and which allowed us to predict some recombination phenomena, the use of such solar cell in optoelectronics. The profile of the photoconductivity also permitted us to utilize a linear model in order to determine an electrical capacitance that varied with magnetic field.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11604202,11674213,61735010 and 51603119the Young Eastern Scholar under Grant Nos QD2015020 and QD2016027+3 种基金the Shanghai Rising-Star Program under Grant No18QA1401700the ‘Chen Guang’ Project under Grant Nos 16CG45 and 16CG46the Shanghai Municipal Education Commissionthe Shanghai Education Development Foundation
文摘Using time-dependent terahertz spectroscopy, we investigate the role of mixed-cation and mixed-halide on the ultrafast photoconductivity dynamics of two different methylammonium(MA) lead-iodide perovskite thin films. It is found that the dynamics of conductivity after photoexcitation reveals significant correlation on the microscopy crystalline features of the samples. Our results show that mixed-cation and lead mixed-halide affect the charge carrier dynamics of the lead-iodide perovskites. In the(5-AVA)_(0.05)(MA)_(0.95) PbI_(2.95) Cl_(0.05)/spiro thin film, we observe a much weaker saturation trend of the initial photoconductivity with high excitation fluence, which is attributed to the combined effect of sequential charge carrier generation, transfer, cooling and polaron formation.
基金This work was financially supported by the National High-Tech Research and Development Pogram of China （＂863＂ Program, Nos. 2002AA325050 and 2004AA302010） the Key Project of Chinese Ministry of Education.（No. 305002）the National Natural Science Foundation of China （Nos. 20325621 and 20236020）.
文摘Functional phthalocyanine （Pc） compounds of H2Pc, TiOPc, FePc and CIAIPc were synthesized with a yield of 46.7%, 91.2%, 37.4% and 34.0%, respectively. Nanosized TiOPc was synthesized via a one-step sol-gel method and effects of surfactant doses, nucleation temperature on TiOPc particle size and photoconductivity were investigated. When re（PEG）： m（TiOPc） was 0.1 and nucleation temperature was 0℃, the as-obtained TiOPc had the smallest particle size and largest specific surface area, which were 60 nm and 83m^2/g, respectively. TiOPc synthesized under these conditions also exhibits excellent photoconductivity with charging potential V0, dark decay speed Rd and energy for half-discharging of potential E1/2 being 1160 V, 30 V/s and 0.6 1x.s, respectively.
文摘Fe (III) 2,9,16,23 tertracarboxy phthalocyanine (Fe (III) taPc) was synthesized, and bonded to polystyrene (PS) with covalence by Friedel Crafts reaction to form a new polymer (Fe (III) taPc PS) (polymer (II)). UV VIS and Infrared spectra indicated that Fe (III) taPc was successfully bonded to PS. A photoreceptor device of sandwich structure consisting of alternate layers of polymer (II) and fullerene (C 60 ) was prepared. The experiment results show that the photoconductivity of the photoreceptor is higher than that of the single layer film of polymer (II) or C 60 , because of the charge transfer effect between the layers.
基金supported by the National Natural Science Foundation of China (52322210, 52172144, 22375069, 21825103, and U21A2069)National Key R&D Program of China (2021YFA1200501)+2 种基金Shenzhen Science and Technology Program (JCYJ20220818102215033, JCYJ20200109105422876)the Innovation Project of Optics Valley Laboratory (OVL2023PY007)Science and Technology Commission of Shanghai Municipality (21YF1454700)。
文摘The utilization of processing capabilities within the detector holds significant promise in addressing energy consumption and latency challenges. Especially in the context of dynamic motion recognition tasks, where substantial data transfers are necessitated by the generation of extensive information and the need for frame-by-frame analysis. Herein, we present a novel approach for dynamic motion recognition, leveraging a spatial-temporal in-sensor computing system rooted in multiframe integration by employing photodetector. Our approach introduced a retinomorphic MoS_(2) photodetector device for motion detection and analysis. The device enables the generation of informative final states, nonlinearly embedding both past and present frames. Subsequent multiply-accumulate (MAC) calculations are efficiently performed as the classifier. When evaluating our devices for target detection and direction classification, we achieved an impressive recognition accuracy of 93.5%. By eliminating the need for frame-by-frame analysis, our system not only achieves high precision but also facilitates energy-efficient in-sensor computing.
文摘The donor-acceptor complex HEC-TCNQ (HEC = 9-hydroxyethylcarbazole; TCNQ = tetracyanoquinodimethane) has been synthesized. Under the illumination of Ar+ laser, the photoinduced charge transfer salt HEC(+)TCNQ(-) can be formed with a conductivity of at least one order of magnitude larger than that of HEC-TCNQ.
基金This work is supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(Nos.2021R1C1C1011219 and2021R1A4A1032085)K.Eomwould like to acknowledge the support by National Research Founda-tion of Korea through the Basic Science Research Program(NRF-2022R1C1C2010693)J.W.Lee acknowledges the support from Ba-sic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2022R1I1A1A01068965).
文摘LaAlO_(3)/SrTiO_(3)(LAO/STO)heterostructures have shown a strong persistent photoconductivity(PPC)at room temperature.The abnormally strong PPC has attracted immense research interest due to its possible applications in optically-tunable electronic devices.Despite its promise,the fundamental understanding of the PPC in the LAO/STO heterostructures is still elusive.Herein,we report that the giant PPC origi-nates from the photo-induced valence change in oxygen vacancies near the LAO/STO interface.Our spec-tral analysis of the photocurrent and the model-fitting study consistently show that the ionized oxygen vacancies near the interface are neutralized during the electron relaxation process.They hinder the complete relaxation of the photoexcited electrons by the deeply-located oxygen vacancies and result in the strong PPC.The change in the ionization state distribution of the oxygen vacancies is probed by the per-sistent noise behavior at the frequency between 1 kHz and 20 kHz regime.These results provide insight into the role of oxygen vacancies in influencing the internal charge distribution and triggering the PPC phenomena in complex oxide heterostructures.
基金This work was supported by the National Natural Science Foundation of China(Nos.50225312,50318001,50433020).
文摘The photoconductivities of a series of novel polyacetylene derivatives （PAs） serving as charge generation materials in the single-layered photoreceptors were investigated using photoinduced xerographic discharge technique. It was found that the substitution can improve the photosensitivity of PAs by increasing the conjugation of π electrons. When the substituent is itself photoconductive, the photoconductivity becomes even higher. It can be concluded from cyclic voltammetry that when the HOMO level of the polymer is closer to that of the charge transport material, the photoconduction performance will be better.
基金Project(NCET-06-0536)supported by the Program for New Century Excellent Talents in University of ChinaProject(Y4090260)supported by the Program for Zhejiang Provincial Natural Sicence Foundation of China
文摘Size-controllable and vertically-oriented TiO2 nanotube(TNT)arrays were fabricated using anodic oxidation method from pure titanium sheets in electrolyte solutions.Then with the TNT arrays as the working electrode,a thin film of polypyrrole(Ppy)was synthesized into the TNT arrays via the electrochemical polymerization.During the process,the appearance of redox peaks in cyclic voltammetry curves of the resulting films indicates the occurrence of polymerization.The morphology,the molecular structure, crystallization and optical properties of the TNT arrays and the resulting polymer were investigated by field-emission scanning electron microscopy(FESEM),X-ray diffractometry(XRD),Fourier transform infrared spectroscopy(FTIR),and UV-vis spectrum analysis,respectively.A dual-layered photoreceptor containing the nanocomposite film as the charge generation layer(CGL)was designed and fabricated.It is found that the photoreceptor based on Ppy/TiO2 nanotubes as CGL exhibits remarkable photoconductive performance.
基金Project supported in part by the National Natural Science Foundation of China(Grant Nos.61974101 and 61971299)the State Key Laboratory of ASIC and System,Fudan University(Grant No.2019KF007)+2 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.SBK2020021406)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.19KJB510058)the Suzhou Science and Technology Bureau(Grant No.SYG201933).
文摘Persistent photoconductivity(PPC)effect and its light-intensity dependence of both enhancement and depletion(E-/D-)mode amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs)are systematically investigated.Density of oxygen vacancy(V O)defects of E-mode TFTs is relatively small,in which formation of the photo-induced metastable defects is thermally activated,and the activation energy(E a)decreases continuously with increasing light-intensity.Density of V O defects of D-mode TFTs is much larger,in which the formation of photo-induced metastable defects is found to be spontaneous instead of thermally activated.Furthermore,for the first time it is found that a threshold dose of light-exposure is required to form fully developed photo-induced metastable defects.Under low light-exposure below the threshold,only a low PPC barrier is formed and the PPC recovery is fast.With increasing the light-exposure to the threshold,the lattice relaxation of metal cations adjacent to the doubly ionized oxygen vacancies(V O^2+)is fully developed,and the PPC barrier increases to∼0.25 eV,which remains basically unchanged under higher light-exposure.Based on the density of V O defects in the channel and the condition of light illumination,a unified model of formation of photo-induced metastable defects in a-IGZO TFTs is proposed to explain the experimental observations.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12261141662, 12074311, and 12004310)。
文摘An in-depth understanding of the photoconductivity and photocarrier density at the interface is of great significance for improving the performance of optoelectronic devices. However, extraction of the photoconductivity and photocarrier density at the heterojunction interface remains elusive. Herein, we have obtained the photoconductivity and photocarrier density of 173 nm Sb2Se3/Si(type-Ⅰ heterojunction) and 90 nm Sb2Se3/Si(type-Ⅱ heterojunction) utilizing terahertz(THz) time-domain spectroscopy(THz-TDS) and a theoretical Drude model. Since type-Ⅰ heterojunctions accelerate carrier recombination and type-Ⅱ heterojunctions accelerate carrier separation, the photoconductivity and photocarrier density of the type-Ⅱ heterojunction(21.8×10^(4)S·m^(-1),1.5 × 10^(15)cm^(-3)) are higher than those of the type-Ⅰ heterojunction(11.8×10^(4)S·m^(-1),0.8×10^(15)cm^(-3)). These results demonstrate that a type-Ⅱ heterojunction is superior to a type-Ⅰ heterojunction for THz wave modulation. This work highlights THz-TDS as an effective tool for studying photoconductivity and photocarrier density at the heterojunction interface. In turn, the intriguing interfacial photoconductivity effect provides a way to improve the THz wave modulation performance.
基金Project supported by the National Basic Research Program (973 Program) (Grant Nos 2007CB310408 and 2006CB302901)the National Natural Science Foundation of China (Grant No 10804077)+1 种基金Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipalitysupported by State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciencs
文摘This paper investigates the ultrafast carrier dynamics and surface photoconductivity of unbiased semi-insulating GaAs in detail by using a terahertz pump-emission technique. Based on theoretical modelling, it finds that transient photoconductivity plays a very important role in the temporal waveform of terahertz radiation pulse. Anomalous enhancement in both terahertz radiation and transient photoconductivity is observed after the excitation of pump pulse and we attribute these phenomena to carrier capture in the EL2 centers. Moreover, the pump power- and temperature- dependent measurements are also performed to verify this trapping model.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51872043,51732003,and 51902049)the National Key R&D Program of China(Grant No.2019YFA0705202)+2 种基金Natural Science Foundation of Jilin Province,China(Grant No.20200201076JC)the National Basic Research Program of China(Grant No.2012CB933703)“111”Project(Grant No.B13013)。
文摘The defect-related photoconductivity gain and persistent photoconductivity(PPC)observed in Ga_(2)O_(3)Schottky photodetectors lead to a contradiction between high responsivity and fast recovery speed.In this work,a metal-semiconductor-metal(MSM)Schottky photodetector,a unidirectional Schottky photodetector,and a photoconductor were constructed on Ga_(2)O_(3)films.The MSM Schottky devices have high gain(>13)and high responsivity(>2.5 A/W)at 230-250 nm,as well as slow recovery speed caused by PPC.Interestingly,applying a positive pulse voltage to the reverse-biased Ga_(2)O_(3)/Au Schottky junction can effectively suppress the PPC in the photodetector,while maintaining high gain.The mechanisms of gain and PPC do not strictly follow the interface trap trapping holes or the self-trapped holes models,which is attributed to the correlation with ionized oxygen vacancies in the Schottky junction.The positive pulse voltage modulates the width of the Schottky junction to help quickly neutralize electrons and ionized oxygen vacancies.The realization of suppression PPC functions and the establishment of physical models will facilitate the realization of high responsivity and fast response Schottky devices.
文摘Persistent photoconductivity has been investigated by various models, among which the Macroscopic Barrier model, Large-Lattice-Relaxation model, and Random Local Potential Fluctuations model are mostly well known. Although the three well-known models have played important roles in describing the persistent photoconductivity, they are not the principal cause of persistent photoconductivity. In this paper a classical model originated from ＂selfmagnetism of electron gas＂ is proposed to illustrate the persistent photoconductivity phenomenon. This classical model is based on electron gas pulsation, which depends on the charge density. Different concentrations of current carriers create different frequencies in the system, and thus the system is sensitive to different wave lengths of incident light. Then the construction of different detectors can be possible for different wave lengths of incident light.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61804136,U1604263,and U1804155)China Postdoctoral Science Foundation(Grant Nos.2018M630829 and 2019T120630).
文摘It is essential to determine the accumulative ultraviolet(UV)irradiation over a period of time in some cases,such as monitoring UV irradiation to the skin,solar disinfection of water,photoresist exposure,etc.UV colorimetric dosimeters,which use dyes'color change to monitor the amount of UV exposure,have been widely studied.However,the exposure data of these UV colorimetric dosimeters can hardly be converted to digital signals,limiting their applications.In this paper,a UV dosimeter has been proposed and demonstrated based on the persistent photoconductivity(PPC)in zinc oxide microwires(ZnO MWs).The PPC effect usually results in high photoconductivity gain but low response speed,which has been regarded as a disadvantage for photodetectors.However,in this work,the unique characteristics of the PPC effect have been utilized to monitoring the accumulative exposure.We demonstrate that the photocurrent in the ZnO MWs depends on the accumulative UV exposure due to the PPC effect,thus the photocurrent can be utilized to determine the UV accumulation.The dosimeter is immune to visible light and exhibits a photoconductive gain of 2654,and the relative error of the dosimeter is about 10%.This UV dosimeter with electrical output is reusable and convenient to integrate with other electronic devices and may also open a new application area for the PPC effect.
