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Growth Habits of Bismuth Selenide (Bi2Se3) layers and nanowires over Stranski–Krastanov Indium Arsenide Quantum Dots
摘要： Bismuth selenide layers and nanowires have been grown by molecular beam epitaxy on self-assembled Stranski–Krastanov InAs quantum dots of different sizes and densities on GaAs substrates. The size and density of the InAs quantum dots were modified by changes in the growth rate and composition. The structure and growth habits of the Bi2Se3 layers were studied by high-resolution x-ray diffraction, scanning probe microscopy, energy-dispersive x-ray spectroscopy and high-resolution electron microscopy. The epitaxial growth of continuous layers of (0001) Bi2Se3 was observed over flat InAs surfaces. In contrast, the presence of InAs quantum dots induced the growth of 100 nm-long and 20 nm-wide Bi2Se3 nanowires primarily oriented along [01-1] and [0-1-1] directions. The nanowires coalesced into full layers when the growth proceeded further. Better understanding and control of the Bi2Se3 growth habits over these surfaces should lead to novel nanostructures with enhanced physical properties.
关键词： InAs quantum dots,Bi2Se3,nanowires,topological insulator,Bismuth selenide,molecular beam epitaxy
更新于2025-09-12 10:27:22
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - As-Se-Te Planar Waveguides Prepared by Continuous and Femtosecond Laser Writing
摘要： As a result of the previous experiments [1], it was found that the Te-based chalcogenide films prepared by plasma deposition have a transparency window in the range from 1.2 to 19 μm and can be modified in the two-photon absorption mode, and in the linear absorption mode only the thermal effects were observed leading to crystallization of the films or their destruction. In this work, PECVD-prepared As-Se-Te films were modified by continuous laser irradiation of different wavelengths – 473, 632.8 and 808 nm. For the modification, samples with compositions As40Se50Te10 and As40Se44Te16 were deposited on a substrate of epi-polished crystalline sapphire. This paper presents the results of studying of the effect of continuous laser radiation on the optical and structural properties of the chalcogenide films samples. Also, planar waveguided structures based on the As-Se-Te films were formed and investigated.
关键词： planar waveguides,continuous laser writing,arsenic selenide films
更新于2025-09-12 10:27:22
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Copper sulfide/ cuprous selenide as a new counter electrode for quantum-dot-sensitized solar cells
摘要： In this paper, the copper sulfide/copper selenide (Cu2S/Cu2Se) composite is presented as a new counter electrode (CE) in the quantum-dot-sensitized solar cells (QDSSCs), for the first time. This novel CE shows a higher electrocatalytic performance towards the polysulfide electrolyte. The obtained results show that, with the change of the CE material from the CuS to the (Cu2S/Cu2Se) composite, the short-circuit current and the cell efficiency are increased from 7.22 to 19.18 mA/cm2 and 1.36 to 4.60%, respectively. The electrochemical impedance spectroscopy (EIS) study and the Tafel polarization analysis demonstrate that the (Cu2S/Cu2Se) CE shows a lower charge transfer resistance in the electrolyte–CE interface, 6.2 ? for the (Cu2S/Cu2Se (5)) CE, in comparison with the pure Cu2S CE, 142.1 ?.
关键词： Cuprous selenide,Copper sulfide,Electrocatalytic performance,Counter electrode,Quantum-dot-sensitized solar cells
更新于2025-09-12 10:27:22
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Size-Programmed Synthesis of PbSe Quantum Dots via Secondary Phosphine Chalcogenides
摘要： In the most common syntheses of colloidal nanocrystal quantum dots (QDs) the size of the particle increases monotonically with reaction time. We have discovered a PbSe QD synthesis whereby size can be easily controlled by varying the side-chains of a secondary phosphine selenide precursor. The reaction runs to completion, and thus a desired QD diameter can be achieved by simply selecting an appropriate secondary phosphine. Quenching of the reaction to select a desired QD size is not required. For different secondary phosphine selenides, measurements of the precursor conversion rate show a direct relationship with final QD size, while P=Se bond strength calculations show an unexpected inverse relationship between QD size and P=Se bond strength. Finally, it is also demonstrated that secondary phosphine selenide precursors can provide an effective route for IV-VI QD syntheses on the large scale.
关键词： colloidal synthesis,size control,IV-VI QDs,secondary phosphine selenide,PbSe quantum dots
更新于2025-09-12 10:27:22
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Optimizing Graphene Content in NiSe/Graphene Nanohybrid Counter Electrode on Boosting Photovoltaic Performance of Dye-sensitized Solar Cells
摘要： Nickel selenide (NiSe) nanoparticles were grown onto different mass ratios of graphene nanosheets (GN) to get their corresponding NiSe/GNx (x= 0.25 to 1.00) nanohybrids by a facile in-situ hydrothermal process to integrate the advantages of high specific surface area of graphene and homogeneously immobilized catalytic sites of NiSe. The nanohybrid having the mass ratio of 1:0.50 (i.e., NiSe/GN0.50) exhibited a higher electrocatalytic activity and electrolyte diffusion. Thus, NiSe/GN0.50 exhibited an improved photo-conversion efficiency (PCE) of 12% (? = 8.62%) than the standard Pt (? = 7.68%) based dye-sensitized solar cell (DSSC). This improved PCE mainly originated from the catalytic ability of NiSe and the multiple interfacial electron transfer pathway of graphene, resulting in the enhanced charge transfer and fast tri-iodide reduction kinetics at the counter electrode/electrolyte interface. The results obtained from the cyclic voltammetry (CV), electrochemical AC-impedance (EIS) and Tafel polarization studies validated the synergistic effect of NiSe and GN and the high possibility of this nanohybrid as an efficient counter electrode (CE) for DSSC.
关键词： Photovoltaic performance,Counter electrode,Graphene nanosheets,Nickel selenide,Dye-sensitized solar cell
更新于2025-09-11 14:15:04
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Ultrahighly Enhanced Performance of Single Cadmium Selenide Nanobelt by Plasmonic Gold Particles
摘要： Noble metal nanoparticles have been demonstrated by a huge application prospect for photodetector (PD) due to their unique and tunable optical properties. Herein, a simple strategy is presented by a combination of gold nanoparticles (Au NPs) and broadband photoresponse cadmium selenide nanobelts (CdSe NBs) to get ultrasensitive, broadband photoresponse (300–720 nm) and tunable photoresponse PD. Concretely, the Au NPs are fabricated on CdSe NBs via ion sputtering and annealing, and the morphology of Au NPs is systematically adjusted by simply tuning the sputter time from 60 to 140 s. Compared with the pure CdSe NB PD, the Au NPs hybrid CdSe NB PD exhibits a high responsivity, especially in the range of 525–575 nm with low light intensity (enhancement of (cid:3)2). The response time of the hybrid PD is (cid:1)2894% at 550 nm with 79.6 μW cm decreased substantially from 0.8 to 0.2 ms. More importantly, the hybrid PD possesses a tunable absorption in the range of 538–580 nm, which is bene?ted from tunable plasmon resonance of Au NPs. These results are con?rmed by the theoretical simulation. It is believed that this strategy offers new opportunities to design ultrasensitive, broadband spectra, and tunable wavelength PD.
关键词： cadmium selenide nanobelts,photodetectors,the discrete dipole approximation,surface plasmon resonances
更新于2025-09-11 14:15:04
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Comparison of Clusters Produced from Sb2Se3 Homemade Polycrystalline Material, Thin Films, and Commercial Polycrystalline Bulk Using Laser Desorption Ionization with Time of Flight Quadrupole Ion Trap Mass Spectrometry
摘要： This study compared Sb2Se3 material in the form of commercial polycrystalline bulk, sputtered thin film, and homemade polycrystalline material using laser desorption ionization (LDI) time of flight mass spectrometry with quadrupole ion trap mass spectrometry. It also analyzed the stoichiometry of the SbmSen clusters formed. The results showed that homemade Sb2Se3 bulk was more stable compared to thin film; its mass spectra showed the expected cluster formation. The use of materials for surface-assisted LDI (SALDI), i.e., graphene, graphene oxide, and C60, significantly increased the mass spectra intensity. In total, 19 SbmSen clusters were observed. Six novel, high-mass clusters—Sb4Se4+, Sb5Se3-6+, and Sb7Se4+—were observed for the first time when using paraffin as a protective agent.
关键词： Antimony selenide,Clusters,Laser desorption ionization,Paraffin,Chalcogenides
更新于2025-09-11 14:15:04
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Enhanced photovoltaic performance of solution-processed Sb2Se3 thin film solar cells by optimizing device structure
摘要： Thin-film solar cells have attracted worldwide attention due to their high efficiency and low cost. Antimony selenide (Sb2Se3) is a promising light absorption material candidate for thin-film solar cells due to its suitable band gap, abundance, low toxicity, and high chemical stability. Herein, we fabricate an Sb2Se3 thin film solar cell using a simple hydrazine solution process. By controlling the thickness of the photoactive layer and inserting a poly(3-hexylthiophene) hole-transporting layer, an Sb2Se3 solar cell with a power conversion efficiency of 2.45% was achieved.
关键词： hole-transporting layer,n-i-p structure,solution process,poly(3-hexylthiophene),antimony Selenide,thin film solar cell
更新于2025-09-11 14:15:04
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Heat degradation of sputter-deposited Cu(In,Ga)Se2 solar cells and modules: Impact of processing conditions and bias
摘要： We report accelerated heat degradation studies on fully encapsulated Cu(In,Ga)Se2 modules as a function of film growth parameters, in particular back contact selenization (preeSe), as well as the impact of bias (light/voltage) during heat degradation. We show that pre-Se conditions have a profound effect on the heat stability of the device, whereby reduced preeSe, while increasing initial efficiency, results in strong heat degradation, driven by a combination of reduced space-charge region and reduced minority carrier lifetime (as evident from external quantum efficiency measurements) in the light-soaked state and resulting in strong degradation of short-circuit current. This is also accompanied by a stronger increase in the shallow acceptor concentration (as measured by capacitance-voltage profiling) in the degraded state, suggesting that the SeeCu divacancy complex (VSe-VCu) is likely responsible. In this case, appearance of a high concentration of deep acceptor states accompanies increased shallow doping upon light-soaking, with the former reducing bulk lifetime and the latter further affecting electron collection due to narrow depletion width. This result suggests that bulk structural properties of the absorber film are strongly impacted by the back contact selenization conditions, making the film more susceptible to heat degradation. In the second part of this paper we show that electrical or light bias during heat exposure reduces degradation, in particular almost fully eliminating the above short-circuit current loss. This is a surprising result as usually the positive effects of bias are attributed to interfacial changes, while our results demonstrate that bulk properties can be improved as well.
关键词： Absorber,Interface,Defects,Thin film solar cell,Heat degradation,Reliability,Light soaking,Copper indium gallium selenide
更新于2025-09-11 14:15:04
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Multistage Degradation Mechanisms in Cu(In, Ga)Se2 Photovoltaic Modules Prepared by Co-Evaporation: Toward High Performances and Enhanced Stability
摘要： This study compared the stability and durability of copper indium gallium selenide (CIGS)-type solar cells prepared using one-step and three-step co-evaporation methods by investigating the causes of degradation in each layer in detail. Measurements recorded using a solar simulator showed that the sample prepared using the three-step method had better device performance owing to the large-grained structure of the CIGS absorber layer, which reduced the carrier recombination. Focusing on the discrepancy in grain size, multifarious degradation tests were conducted according to the IEC 61646 standard to evaluate the stability of the cells under harsh environments such as high humidity (85 %), high temperature (85 ℃), and mechanical load. Damp heat (85 %/85 ℃) did not affect the CIGS resistivities in either sample, whereas all the aluminum-doped zinc oxide layers degraded, as determined by confirming the chemisorbed oxygen by exposure to a hot, humid environment. After 200 thermal cycles, the CIGS layers in both samples were mainly degraded while there were no changes in the resistivities of the AZO layer in either sample. The thermal cycling test highlights that the initial resistivities of the one-step sample showed a decisive change before and after thermal cycling compared to the three-step sample. This change might be caused carriers being scattered at the grain boundaries. Although there were no big differences in the FT-IR spectra before and after thermal cycling, both XRD and XPS results confirmed that not only copper indium sulfide selenium elements of secondary phase were newly observed by sulfide diffusion from the CdS layer, but also that each element (Cu, In, Ga, and Se) was slightly oxidized by the rapid temperature variation from ?45 ℃ to 85 ℃. These results prove that the three-step co-evaporation method can produce cells with much higher stability and durability, even when operated under high humidity and temperature conditions.
关键词： Degradation mechanism,Copper indium gallium selenide,Co-evaporation,Grain size,Stability,Aluminum-doped zinc oxide
更新于2025-09-11 14:15:04