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[IEEE 2018 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Hangzhou, China (2018.8.13-2018.8.17)] 2018 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Growth and Optical Properties of ZnSe Nanofilms Obtained from Modified Ammonia-free Chemical Bath Solution
摘要： ZnSe nano thin films were obtained with chemical bath deposition in an modified aqueous alkaline solution in which ammonia was eliminated complexing agent in our present work. The as-deposited films are transparent, specula reflective and homogenous. Energy-dispersive X-ray spectroscopy indicated that films were in near stiochiometric Zn:Se ratio. Measured by spectroscopic ellipsometry, thickness of 50~370nm film can be obtained, the ZnSe were in nano-films, morphology and the film formation process discussion indicated that the film grow through nano-cluster by nano-cluster deposition rather than ion by ion mechanism. Absorption of the annealed films in visible light area indicated that bandgap is around 2.8eV for the annealed ZnSe film obtained from modified ammonia free solutions, corresponding to the standard band gap for bulk ZnSe materials.
关键词： Growth Kinetics,ZnSe Films,Optical Properties,Chemical Bath solution
更新于2025-09-23 15:23:52
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Nonlinear transmittance of a diffusion-doped single crystal ZnSe:Fe <sup>2+</sup> at a wavelength of 2940?nm at low and room temperature
摘要： The nonlinear transmittance of a single crystal ZnSe:Fe2+ sample was measured at low and room temperature during the action of a laser pulse with a wavelength of 2940 nm. It was found that in a strong field (fluence 1.3 J cm?2, a laser pulse duration of 320 ns, a peak intensity of 4.1 MW cm?2), the sample transmittance is about 70% at room and 77% at low temperature. In a single crystal ZnSe:Fe2+ sample at a fluence of 1.3 J cm?2 and a spot diameter of high-power radiation of about 0.54 mm, at the temperature ?168 °C lasing was observed along the surface of the sample, when feedback was provided by scattering from the matted surface of the sample. This effect should be taken into account when nonlinear transmittance measurements are fulfilled of a diffusion doped a single crystal ZnSe:Fe2+.
关键词： nonlinear transmittance,ZnSe:Fe2+,low temperature
更新于2025-09-23 15:22:29
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Preparation of radial ZnSe-CdS nano-heterojunctions through atomic layer deposition method and their optoelectronic applications
摘要： Radial 1-D nano-heterojunctions have distinct optoelectronic properties. However, their complex fabrication process is still the bottleneck of device applications. Herein, a facile atomic layer deposition (ALD) method was used to coat a polycrystalline CdS thin film with high uniformity and controllable thickness on the surface of the as-synthesized p-type ZnSe nanowires, for fabricating radial 1-D ZnSe-CdS nano-heterojunctions. The nano-heterojunctions exhibited excellent optoelectronic properties. Under blue/violet light, the nano-heterojunctions obtained a response radio of ~5 × 10^3, a responsitivity of ~1.43 A/W, a gain of ~3.78 and a detectivity of ~0.57 × 10^12 cmHz^{1/2}W^{-1} at zero bias. Furthermore, the nano-heterojunction also showed obvious photovoltaic characteristic with a power conversion efficiency of ~0.96%. This method is expected to play an important role in nano-heterojunction construction and their device applications.
关键词： ZnSe,CdS,Photovoltaic,Nano-heterojunction,Atomic layer deposition,Photodetector
更新于2025-09-23 15:22:29
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The phase transition and optical properties of Cr2+-doped ZnSe under high pressure
摘要： The phase transition pressure, electronic structure, optical properties and stability for ZnSe and Cr2+:ZnSe with different doping concentrations were calculated by first-principles calculation based on density-functional theory. The phase transition pressure was calculated by enthalpy-pressure relation. The introduction of dopant (Cr2+) reduces the phase transition pressure, and the phase transition pressure decreases with the increase of doping concentration. The high pressure enhances the degeneracy of Cr-d orbitals. Under the high-pressure conditions, the absorption peak positions of Cr2+:ZnSe have obvious blue-shift. Meanwhile, the stability of structures for ZnSe and Cr2+:ZnSe were further confirmed by defect formation energy and elastic constants.
关键词： Phase transition pressure,Cr2+:ZnSe,First-principles calculation,Optical properties
更新于2025-09-23 15:22:29
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Surface and intrinsic contributions to extinction properties of ZnSe quantum dots
摘要： This work studies extinction properties of ZnSe quantum dots terminated with either Se-surface or Zn-surface (Se-ZnSe or Zn-ZnSe QDs). In addition to commonly observed photoluminescence quenching by anionic surface sites, Se-ZnSe QDs are found to show drastic signatures of Se-surface states in their UV–visible (Vis) absorption spectra. Similar to most QDs reported in literature, monodisperse Zn-ZnSe QDs show sharp absorption features and blue-shifted yet steep absorption edge respect to the bulk bandgap. However, for monodisperse Se-ZnSe QDs, all absorption features are smeared and a low-energy tail is identified to extend to an energy window below the bulk ZnSe bandgap. Along increasing their size, a cyclic growth of ZnSe QDs switches their surface from Zn-terminated to Se-terminated ones, which confirms that the specific absorption signatures are reproducibly repeated between those of two types of the QDs. Though the extinction coefficients per unit of Se-ZnSe QDs are always larger than those of Zn-ZnSe QDs with the same size, both of them approach the same bulk limit. In addition to contribution of the lattice, extinction coefficients per nanocrystal of Zn-ZnSe QDs show an exponential term against their sizes, which is expected for quantum-confinement enhancement of electron–hole wavefunction overlapping. For Se-ZnSe QDs, there is the third term identified for their extinction coefficients per nanocrystal, which is proportional to the square of size of the QDs and consistent with surface contribution.
关键词： ZnSe,quantum dots,surface state,extinction coefficient
更新于2025-09-23 15:21:01
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Quantum dot material engineering boosting quantum dot sensitized solar cells efficiency over 13%
摘要： The intrinsic electronic structure and crystalline quality of quantum dot (QD) light-harvesting materials are among the primary reasons in determining the photovoltaic performance of resulting QD sensitized solar cells (QDSCs). Undoubtedly, exploiting appropriate high-quality QDs is a crucial route to improve the performance of QDSCs. In order to reduce the density of trap state defects, a ZnSe shell layer with wider bandgap is overgrown around the light-harvesting star material Zn-Cu-In-Se (ZCISe) alloy QDs to form the type-I core/shell structured ZCIS/ZnSe. Through this QD material engineering, average power conversion efficiency (PCE) of QDSCs was improved from 9.54% corresponding to pristine CuInSe2, to 12.49% from alloyed ZCISe, and to 13.71% for core/shell structured ZCISe/ZnSe QDs. A certified PCE of 13.49% has been obtained for the ZCIS/ZnSe QDSCs under AM 1.5G one sun irradiation. This value is a new record efficiency for QDSCs. The remarkable enhancement of photovoltaic performance for ZCIS/ZnSe-based QDSCs vs. ZCISe ones is mainly ascribed to the reduced density of trap state defects, which favours the suppression of charge recombination at photoanode/electrolyte interfaces and hence improves the photovoltage and fill factor, particularly. The steady state optical spectroscopy, diode ideality factor, transient absorption, and electrochemical impedance spectroscopy characterizations confirm that the formed type-I core/shell structure can reduce the density of trap state defects and suppress charge recombination and improve the photovoltaic performance of the resulting cells. This work demonstrates the great potential of QD material engineering in improving the photovoltaic performance of QDSCs.
关键词： sensitized solar cells,photovoltaic performance,quantum dot,ZnSe,Zn-Cu-In-Se
更新于2025-09-23 15:21:01
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Effect of indium alloying on the charge carrier dynamics of thick-shell InP/ZnSe quantum dots
摘要： Thick-shell InP/ZnSe III–V/II–VI quantum dots (QDs) were synthesized with two distinct interfaces between the InP core and ZnSe shell: alloy and core/shell. Despite sharing similar optical properties in the spectral domain, these two QD systems have differing amounts of indium incorporation in the shell as determined by high-resolution energy-dispersive x-ray spectroscopy scanning transmission electron microscopy. Ultrafast fluorescence upconversion spectroscopy was used to probe the charge carrier dynamics of these two systems and shows substantial charge carrier trapping in both systems that prevents radiative recombination and reduces the photoluminescence quantum yield. The alloy and core/shell QDs show slight differences in the extent of charge carrier localization with more extensive trapping observed in the alloy nanocrystals. Despite the ability to grow a thick shell, structural defects caused by III–V/II–VI charge carrier imbalances still need to be mitigated to further improve InP QDs.
关键词： indium alloying,InP/ZnSe,charge carrier dynamics,photoluminescence quantum yield,quantum dots
更新于2025-09-23 15:21:01
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All-fiber passively Q-switched erbium-doped laser with Cr <sup>2+</sup> :ZnSe nanocrystals saturable absorber
摘要： We experimentally demonstrate an all-fiber Q-switched erbium-doped laser using polyvinyl alcohol-based Cr2+:ZnSe nanocrystals (NCs) as saturable absorbers (SAs). The Cr2+:ZnSe NCs were produced by femtosecond laser ablation, and were spherical, with an average radius of about 107 nm. The nonlinear saturable absorption was characterized with a saturable optical intensity of 20 MW cm?2 and a modulation depth of ～24%. By placing the SA inside an erbium-doped fiber (EDF) laser cavity, a stable 3.152 μs pulse with a repetition rate of 34.452 kHz centered at 1564 nm was achieved, when pumped at the maximum pumping power of 300 mW. The maximum pulse energy reached 33 nJ and the signal-to-noise ratio was 48 dB. The results indicate that Cr2+:ZnSe NCs are promising for the development of a stable all-fiber passively Q-switched EDF laser.
关键词： Cr2+: ZnSe nanocrystals,passively Q-switched,all-fiber laser
更新于2025-09-23 15:21:01
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ZnSe:Te/ZnSeS/ZnS Nanocrystals: An Access to Cadmium-Free Pure-Blue Quantum-Dot Light-Emitting Diodes
摘要： Cadmium-free quantum dots (QDs) are attracting considerable research attention because of their low toxicity. However, the bandgap of most cadmium-free QDs avoids the pure-blue region, which confers difficulty in realizing pure-blue quantum-dot light-emitting diodes (QLEDs). In this work, we successfully tuned the emission wavelength of ZnSe/ZnS quantum dots from the violet region (~ 420 nm) to the pure-blue region (450 – 460 nm) by doping Te into the ZnSe core. The ZnSe:0.03Te/ZnSeS/ZnS QDs sample with an emission position of 450 nm and quantum yield of 30% was the most balanced formula. To overcome the energy gap between the hole-transfer layer and QD layers, a specific hole-transfer layer was developed for normal-structure QLEDs. Such structure QLED by ZnSe:0.03Te/ZnSeS/ZnS QDs achieved the pure-blue light emission at 455 nm, a low turn-on voltage of 4.4 V, and external quantum efficiency of 0.33%. Overall, our cadmium-free QLED achieved pure-blue emission, revealing the potential of ZnSe-based pure-blue QLEDs for future displays.
关键词： Pure-blue emission,Cadmium-free,QLEDs,Quantum dots,ZnSe
更新于2025-09-23 15:21:01
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Temperature-Controlled Fragmentation and Ripening: Synthesis of ZnSe Nanorods with Variable Dimensions and Crystal Structure Starting from Ultrathin ZnSe Nanowires
摘要： Heavy-metal-free semiconductor nanomaterials have attracted attention because of their importance in both fundamental research and commercial applications. In particular, polarized ?uorescence emission in one-dimensional (1D) semiconductors makes them highly attractive as display materials. Herein, we developed a novel colloidal synthesis approach toward 1D ZnSe nanostructures with controlled size and crystal structure, which we call “temperature-controlled fragmentation and ripening”. First, ultrathin ZnSe nanowires (NWs) with a length of 50?200 nm and diameter of ～1.1 nm were synthesized. ZnSe nanorods (NRs) have been obtained through the fragmentation of these NWs in a controlled step while keeping the same diameter, and the length of the ?nal ZnSe NRs has been tuned in the range of 10?20 nm by moderating the heating procedure. Using a higher temperature for fragmentation allowed us to break down the ZnSe NWs to shorter ZnSe NRs, whereas controlling the ?nal growth temperature of the ZnSe NRs in a subsequent ripening stage allowed us to obtain them in either cubic zinc blende (ZB; at 220 °C) or hexagonal wurtzite (WZ; at 240 °C) crystal structures. This set of growth processes ?ipping from bottom-up to top-down to form ZnSe NRs with controlled length and selection of the ?nal crystal structure (either hexagonal WZ or cubic ZB) provides a novel growth mechanism to synthesize 1D semiconductor nanostructures.
关键词： nanorods,ripening,nanowires,temperature-controlled fragmentation,ZnSe,crystal structure
更新于2025-09-23 15:19:57