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Enhanced X-ray sensitivity of MAPbBr3 detector by tailoring the interface-states density
摘要： An important factor for the high performance of light-harvesting devices is the presence of surface trappings. Therefore, understanding and controlling the carrier recombination of the organic-inorganic hybrid perovskite surface is critical for the device design and optimization. Here, we report the use of aluminum zinc oxide (AZO) as the anode to construct a p-n junction structure MAPbBr3 nuclear radiation detector. The AZO/MAPbBr3/Au detector can tolerate an electrical field of 500 V·cm-1 and exhibit a very low leakage current of ~9 nA, which is one order of magnitude lower than that of the standard ohmic contact device. The interface state density of AZO/MAPbBr3 contact was reduced from 2.17×1010 cm-2 to 8.7×108 cm-2 by annealing at 100 °C under Ar atmosphere. Consequently, a photocurrent to dark current ratio of 190 was realized when exposed to a green LED with a wavelength of 520 nm (~200 mW·cm?2). Simultaneously, a high X-ray sensitivity of ~529 μC·Gyair-1cm-2 was achieved under 80 kVp X-ray at an electric field of 50 V·cm-1. These results demonstrate the use of surface engineering to further optimize the performance of MAPbBr3 detectors, which have many potential applications in medical and security detection with low radiation dose brought to the human body.
关键词： p-n junction,annealing,X-ray detector,MAPbBr3 PSC,interface states density
更新于2025-09-19 17:15:36
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Explaining the enhanced photoelectrochemical behavior of highly-ordered TiO2 nanotube arrays: anatase/rutile phase junction
摘要： The effect of calcination temperature on the photoelectrochemical properties of TiO2 nanotube arrays (TNTAs) has been investigated in many studies. Most work focused on improving the photoelectrochemical properties through optimization of the microstructure. In this paper, however, an anatase/rutile phase junction formed in TiO2 nanotubes has been demonstrated to account for the enhancement of the photoelectrochemical performance. Observations by the UV-visible diffuse reflectance spectra, glancing incidence angle X-ray diffraction (GIA-XRD) and electrochemical impedance spectroscopy indicate that the rutile fraction is at the bottom of the nanotubes while the anatase fraction at the body of the nanotubes. The TNTAs with the coexistence of about 60% anatase and 40% rutile exhibit the optimal performance and show the 1.4 times improved photocurrent density compared with the pure anatase TNTAs. Detailed synchrotron radiation photoemission spectroscopy further confirms the existence and effect of the phase junction. The results suggest photogenerated electrons transfer from the rutile phase to anatase phase in the nanotubes due to the band edge alignment, which facilitates the photogenerated carriers separation and transport along the nanotubes and leads to apparent enhancement of the photoelectrochemical behavior.
关键词： photoelectrochemical properties,TiO2 nanotube arrays,phase junction,thermal treatment
更新于2025-09-19 17:15:36
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Fluorescence contrast-enhanced proliferative lesion imaging by enema administration of indocyanine green in a rat model of colon carcinogenesis
摘要： The fluorescent contrast agent indocyanine green (ICG) is approved by the Food and Drug Administration for clinical applications. We previously reported that cultured human colon tumor cells preferentially take up ICG by endocytic activity in association with disruption of their tight junctions. The present study explored ICG availability in fluorescence imaging of the colon to identify proliferative lesions during colonoscopy. The cellular uptake of ICG in cultured rat colon tumor cells was examined using live-cell imaging. Colon lesions in rats administered an ICG-containing enema were further assessed in rats with azoxymethane-induced colon carcinogenesis, using in vivo endoscopy, ex vivo microscopy, and immunofluorescence microscopy. The uptake of ICG by the cultured cells was temperature-dependent. The intracellular retention of the dye in the membrane trafficking system suggested endocytosis as the uptake mechanism. ICG administered via enema accumulated in colon proliferative lesions ranging from tiny aberrant crypt foci to adenomas and localized in proliferating cells. Fluorescence endoscopy detected these ICG-positive colonic proliferative lesions in vivo. The immunoreactivity of the tight-junction molecule occludin was altered in the proliferative lesions, suggesting the disruption of the integrity of tight junctions. These results suggest that fluorescence contrast-enhanced imaging following the administration of an ICG-containing enema can enhance the detection of mucosal proliferative lesions of the colon during colonoscopy. The tissue preference of ICG in the rat model evaluated in this study can be attributed to the disruption of tight junctions, which in turn promotes endocytosis by proliferative cells and the cellular uptake of ICG.
关键词： colon tumor,endoscopy,fluorescence imaging,indocyanine green,tight junction
更新于2025-09-19 17:15:36
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Field Characteristics of Spin-Torque Diode Sensitivity in the Presence of a Bias Current
摘要： The use of the spin-torque diode effect, which is generated upon the current-induced transfer of spin angular momentum in magnetic tunnel junctions, opens the prospect of considerably improving microwave sensitivity in the gigahertz frequency band over that of semiconductor Schottky diodes. In this work, the spin-diode effect of microwave signal rectification in a magnetic tunnel junction upon the resonant excitation of spin waves in the free magnetic layer as a result of the current-induced spin-transfer torque effect is analyzed theoretically. Frequency characteristics of the resonant response of a spin-torque diode to a microwave signal are calculated in the linear macrospin approximation as functions of the direction and value of the applied magnetic field and bias current. It is shown that with zero bias current, the maximum rectified voltage across a junction is obtained in the geometry of mutually perpendicular magnetizations of magnetic layers; as the resonant frequency of oscillations in a magnetic field increases, this voltage drops at the retained equilibrium orientation of spins in the layers. After the bias current is switched on, the resonance amplitude of forced oscillations of the free layer spins upon microwave excitation grows sharply at the critical point of the spin-torque diode's loss of equilibrium state stability. The linewidth at this point is limited only by nonlinear effects. Improving spin-torque diode sensitivity is important for its use in microwave holographic vision systems.
关键词： macrospin model,microwave sensitivity,ferromagnetic resonance,magnetic tunnel junction,portable spin-torque diode
更新于2025-09-19 17:15:36
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The maximum rectification ratio of pyrene-based molecular devices: a systematic study
摘要： We apply the NEGF + DFT technique to study the effect of anchoring groups on the electronic transport properties of a single pyrene molecule attached to two Au electrodes via three different anchoring groups (namely NO2, NH2 and CN). More specifically, we investigate the effect of asymmetric electrode coupling together with B and N doping on rectification ratio of a pyrene-based molecular device. The results indicate that the rectification ratio can be tuned by selecting configurations of maximum difference in the coupling parameters in the two sides of the gold electrodes, and its magnitude depends on the strength of the electronic coupling of the pyrene molecule to the gold electrodes. In addition, we observe that doping the molecule with B and N atoms decreases the coupling parameters by creating a resonant peak close to the Fermi level.
关键词： Non-equilibrium Green's function method,Molecular junction,Pyrene,Doping,Rectification ratio
更新于2025-09-19 17:15:36
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Determining combined effects of solar radiation and panel junction temperature on all model-parameters to forecast peak power and photovoltaic yield of solar panel under non-standard conditions
摘要： In the current study, we introduce two methods to extract model-physical parameters of a solar panel using photovoltaic metrics at key points. We use a single-diode circuit to describe a solar panel working under STC. According to the first method, we derive a new transcendental equation connecting series resistance Rs to quality factor η and photovoltaic metrics at key points. Following the second method, we establish a new analytic expression giving series resistance as a function of quality factor and key points coordinates. For both methods, we express parallel conductance Gp, photo-generation current Iph and leakage current Is in terms of quality factor and all photovoltaic metrics. We use quality factor as variational parameter to minimize RMSE between experimental and optimized characteristics. We borrow temperature coefficients from manufacturer data sheet and determine panel radiation coefficients to derive analytical expressions giving variations of photovoltaic metrics at key points as functions of panel junction temperature T and solar radiation S. To investigate dependencies of all model-physical parameters versus T and S, we consider numerical values of model-physical parameters at STC as initial conditions, and resolve the system of non-linear equations linking panel current to panel voltage at key points. We test numerical models established and mathematical expressions derived by specifying to PV solar panels such as KC130GT and SM55 operating at different environmental conditions of ambient temperature and solar radiation. As a result, for arbitrary environmental conditions, predicted characteristics agree with measured characteristics validating thereby our numerical approach.
关键词： Model-physical parameters extraction,Solar radiation effect,Panel junction temperature coefficients,Solar radiation coefficient,Panel junction temperature effect,Current-voltage characteristics
更新于2025-09-19 17:13:59
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Co-electrodeposited Cu2ZnSnS4 thin films for P-N junction photovoltaics and dye sensitized solar cells
摘要： Copper Zinc Tin Sulphide (Cu2ZnSnS4/CZTS) thin films were deposited on fluorine/indium doped tin oxide (FTO/ITO) coated glass substrates by one step electrodeposition method followed by annealing in nitrogen gas carrying sulphur vapors for 15 min. Formation of pure Cu2ZnSnS4 phase was confirmed by X-Ray Diffraction and Raman spectroscopy. Surface morphology of the films was analyzed using field emission scanning electron microscopy. Optical measurements using UV–visible spectroscopy showed absorption coefficients in the order of 104–105 cm?1 and optical band gap of ～1.48 eV. Simple p-n junctions were formed by electrodepositing CZTS on cadmium sulphide thin films coated over ITO substrates and subsequent annealing. Current-voltage (I–V) characteristics of the junction showed a knee voltage of about 0.9 V indicating that a good open circuit voltage (Voc) can be obtained from a solar cell constructed using this junction. CZTS films deposited on FTO substrates were used as counter electrode (CE) in dye sensitized solar cell (DSSC) to demonstrate CZTS as a potential substitute to the conventional platinum CE. Performance of the DSSC with CZTS CE was evaluated in comparison to Pt by determining the I-V characteristics under 1 sun illumination. The DSSC showed Voc of 0.77 V, short circuit current density of 1.85 mAcm?2, fill factor of 70.4% and 1% power conversion efficiency.
关键词： Non-hydrazine route,Solar energy material,Counter electrode,P-n junction,Co-electrodeposition,Dye sensitized solar cell
更新于2025-09-19 17:13:59
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Graphene/HgTe Quantum-Dot Photodetectors with Gate-Tunable Infrared Response
摘要： Graphene-based vertical heterostructures are of interest as emerging electronic and optoelectronic devices. Here, we report the study of photovoltaic response from graphene/HgTe quantum-dot junction. The graphene/HgTe quantum-dot junction combines the high carrier mobility of graphene and tunable infrared optical absorption of HgTe colloidal quantum dots, which offers promising route for the next-generation infrared optoelectronics. We demonstrate that both the sign and magnitude of the short-circuit photocurrents and open-circuit voltages can be controlled by the applied gate voltage, which tunes the Fermi level and the interfacial built-in potential across the junction. The interfacial energy band diagram is deduced to provide the fundamental understanding of the essential physics behind the graphene/quantum-dot film junction.
关键词： graphene/HgTe CQDs junction,photovoltaic detection,interfacial photocarrier transport,gate-tunable photoresponse,infrared
更新于2025-09-19 17:13:59
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Characteristics enhancement of one-section and two-stepwise microchannels for cooling high-concentration multi-junction photovoltaic cells
摘要： This paper presents the development of simple, effective, and economic microchannel systems for cooling high-concentration multi-junction photovoltaic (HCMJPV) cells. The developed cooling system uses a short cooling fluid path concept with either one or two microchannel sections per the fluid path. The work is conducted using a 3D numerical model that is based on the finite volume method. The effects of design parameters on the thermal characteristics of one and two-section microchannels and output power of the HCMJPV cells are comprehensively investigated. Cooling systems that attained the largest net output power of HCMJPV cells are identified. Developed cooling systems achieved superior characteristics compared to the existing state of the art system. The two-stepwise microchannel cooling system achieves the best temperature uniformity, whereas the constant-width one-section microchannel cooling system achieves slightly better characteristics than the two-stepwise system. The proposed constant-width one-section cooling system achieves comparable standard deviation and lower surface temperature (35.65 °C), pressure drop (68.41%) and microchannel thermal resistance (49.57%) along with higher generated power (8.27%), net output power (8.44%) and overall heat transfer coefficient (175.8%) than the existed cooling system in literature. The developed cooling system allows the cells to produce an extra 820.5MWh/m2 of cells during their lifetime.
关键词： Hybrid jet impingement-microchannel cooling,Pumping power,High-concentration multi-junction photovoltaic,Stepwise microchannel cooling,High power integrated circuits,Net output power
更新于2025-09-19 17:13:59
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Tuneable efficiency of direct growth graphene solar cells
摘要： Direct growth technique could produce low-cost, high-efficiency graphene-on-silicon Schottky junction solar cells. The team from Sejong University, Korea, report on their latest development – a low cost fabrication technique, which allows different thicknesses of graphene to be grown directly onto bare silicon. The efficiency of the cell was further increased to 9.18 % by adding and doping a polymer (PMMA) layer. The authors say that their direct growth technique is 'compatible for industrial-level applications,' and suggest that it offers a simpler and more reliable alternative to manually transferring CVD-grown graphene onto a silicon surface.
关键词： solar cells,graphene,efficiency,Schottky junction,direct growth
更新于2025-09-19 17:13:59