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Femtosecond-Laser-Induced Precipitation of CsPbBr3 Perovskite Nanocrystals in Glasses for Solar Spectral Conversion
摘要： Inorganic perovskite quantum dots (QDs) and nanocrystals (NCs) have attracted much attention in recent years because of their high photoluminescence quantum yield (PL QY), narrow full width at half maximum, and wide tunability cross the whole visible range. In this work, space- and size-controlled precipitation of CsPbBr3 perovskite NCs was realized through femtosecond laser direct writing method. Precipitation of CsPbBr3 NCs in glasses was confirmed by the energy dispersive spectroscopy, transmission electron microscope analysis and photoluminescence (PL). Growth of CsPbBr3 perovskite NCs in glass was modulated by fs laser irradiation parameters such as repetition rate, pulse energy, and scanning rate, and PL in the range spanning from blue to green was achieved. With well-designed arrangement of CsPbBr3 NCs and the reduction of self-absorption emission, solar concentrator fabricated by fs laser irradiation can realize the spectral conversion and enhance the quantum efficiency of solar cells.
关键词： Glass,All-inorganic perovskite,Spectral conversion,Solar concentrator,Femtosecond laser,Photoluminescence,CsPbBr3,Nanocrystals
更新于2025-09-12 10:27:22
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The electronic and optical properties of an exciton, biexciton and charged excitons in CdSe/CdTe-based multi-shell type-II quantum dot nanocrystals
摘要： It has been recently reported that multi-shell type-II quantum dot nanocrystals (QDNCs) have higher quantum yields. Besides these higher quantum yields of multi-shell type-II QDNCs, additional second layer has been a critical influence on the formation mechanisms of the excitonic structures. Understanding of bound and unbound cases of the excitonic structures in multi-shell type-II QDNCs gives some important information for applications. In this study, we have investigated the electronic and optical properties of a single exciton (X), biexciton (XX), and positively and negatively charged excitons ( ??+ and ??? ) in CdSe/CdTe-based multi-shell type-II QDNCs. In the study, three different structure compositions, i.e., CdSe/CdTe, CdSe/CdTe/CdS, and CdSe/CdTe/ZnTe, have been considered. We have observed that CdS and ZnTe materials have drastically changed the electronic and optical properties of the bare CdSe/CdTe type-II QDNCs.
关键词： Exciton,CdS,Biexciton,CdSe/CdTe,Charged excitons,ZnTe,Quantum dot nanocrystals,Type-II
更新于2025-09-12 10:27:22
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Core/Shell Nanocrystal Tailored Carrier Dynamics in Hysteresis-Less Perovskite Solar Cell with ~20% Efficiency and Long Operational Stability
摘要： The ambient stability, hysteresis and trap states in organo-halide perovskite solar cells (PSCs) are correlated to the influence of interlayer interfaces and grain boundaries. Astute incorporation of Cu2ZnSnS4 (CZTS) and Au/CZTS core/shell nanocrystals (NCs) can achieve the goal of simultaneously achieving better performance and ambient stability of the PSCs. With optimized Au/CZTS NC size and concentration in the photoactive layer, power conversion efficiency can be increased up to 19.97±0.6% with ambient air stability ?800 h, as compared to 14.46±1.02% for the unmodified devices. Through efficient carrier generation by CZTS and perovskite, accompanied by the plasmonic effect of Au, carrier density is sufficiently increased as validated from transient absorption spectroscopy. NCs facilitate the interfacial charge transfer by suitable band alignment, and removal of recombination centers such as metallic Pb0, surface defects or impurity sites. NC-embedding also increases the perovskite grain size and assist in pin-hole filling, reducing the trap state density.
关键词： Carrier Dynamics,Perovskite Solar Cells,Plasmonics,Optoelectronics,Energy Conversion and Storage,Operational Stability,Hysteresis-Less,Core/Shell Nanocrystals
更新于2025-09-12 10:27:22
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Unraveling the Moisture-induced Decomposition Mechanism of Red-Emitting Perovskite CsPbBrI <sub/>2</sub> Nanocrystals and Enhancing their Stability through Copper(II) Substitution
摘要： The red-Emitting perovskite CsPb(BrxI1-x)3 (0<x<1) nanocrystals (NCs) is hindered because of their low structural stability, and the moisture-induced degradation pathways of these red-Emitting perovskite are not well-defined. In the present work, we show that the moisture-induced degradation of CsPbBrI2 NCs spontaneously forms CsPbBr3 (α) and CsPbI3(δ) and other decomposition products. On the other hand, highly stable and luminescent red perovskite CsPbBrI2 NCs were achieved through copper substitution and halide rich passivation strategy. We demonstrated that the incorporation of Cu2+ ions can enhance formation energy, causing a slight lattice contraction, and hence stabilize the cubic phase of these NCs. Cu2+-substituted CsPbBrI2 NCs with higher luminescence were synthesized in a halide-rich passivation method. The highly stable and luminescent Cu2+-substituted CsPbBrI2 NCs can function well as efficient light emitters toward fabrication of the high-performance red perovskite LEDs.
关键词： perovskite nanocrystals,stability,CsPbBrI2,copper-substitution,light-emitting diodes
更新于2025-09-12 10:27:22
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Ionically Modified Cellulose Nanocrystal Self-Assembled Films with a Mesoporous Twisted Superstructure: Polarizability and Application in Ion-Gated Transistors
摘要： Mesoporous structures made of cellulose nanocrystals (CNCs) and their self-assembly into films is of great interest not only due to their abundancy and sustainability but also due to their ease of chemical modification and nanoscale bio mimicry capabilities. However, their implementation in (opto)electronic devices requires further understanding on how these self-assembled twisted mesoporous superstructures respond to electrical stimulus. In this regard, this work focusses in the infiltration with three distinct alkali ions (Li+, Na+ and K+) to yield films with improved electrochemical response when compared to pristine ones, while preserving their photonic character. Electrochemical characterization shows capacitances of up to 2.5 μF cm-2 allowing for their integration as solid-state gate electrolytes in amorphous indium-gallium-zinc-oxide transistors, resulting in low operating voltages (< 2 V), On/Off ratios of up to 6 orders of magnitude and high saturation mobilities >10 cm2 V-1 s-1. Devices fabricated on Na+ and K+ infiltrated CNC films present the best characteristics, indicating pure capacitive charging of the semiconductor. The insights presented here contribute to applications in solid-state ionics in mesoporous structures or the combination of optically active electrolytes capable of providing unique functionalities in ion-gated transistors and circuitry.
关键词： Self-assembly,Mesoporous Structures,Cellulose Nanocrystals,Ion Gated Transistors,Photonics
更新于2025-09-12 10:27:22
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Plasmonic Metamaterial Gels with Spatially Patterned Orientational Order via 3D Printing
摘要： Optical properties can be programmed on mesoscopic scales by patterning host materials while ordering their nanoparticle inclusions. While liquid crystals are often used to define the ordering of nanoparticles dispersed within them, this approach is typically limited to liquid crystals confined in classic geometries. In this work, the orientational order that liquid crystalline colloidal hosts impose on anisotropic nanoparticle inclusions is combined with an additive manufacturing method that enables engineered, macroscopic three-dimensional (3D) patterns of co-aligned gold nanorods and cellulose nanocrystals. These gels exhibit polarization-dependent plasmonic properties that emerge from the unique interaction between the host medium’s anisotropic optical properties defined by orientationally ordered cellulose nanocrystals, from the liquid crystal’s gold nanorod inclusions, and from the complexity of spatial patterns accessed with 3D printing. The gels’ optical properties that are defined by the interplay of these effects are tuned by controlling the gels’ order, which is tuned by adjusting the gels’ cellulose nanocrystal concentrations. Lithe optical responsiveness of these composite gels to polarized radiation may enable unique technological applications like polarization-sensitive optical elements.
关键词： liquid crystals,optical properties,nanoparticles,plasmonic properties,cellulose nanocrystals,gold nanorods,3D printing
更新于2025-09-12 10:27:22
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Bandgap Tunable Ternary Cd <sub/><i>x</i> </sub> Sb <sub/> 2– <i>y</i> </sub> S <sub/>3?δ</sub> Nanocrystals for Solar Cell Applications
摘要： We report the synthesis and photovoltaic performance of a new nonstoichiometric ternary metal sulfide alloyed semiconductor?CdxSb2?yS3?δ nanocrystals prepared by the two-stage sequential ionic layer adsorption reaction technique. The synthesized CdxSb2?yS3?δ nanocrystals retain the orthorhombic structure of the host Sb2S3 with Cd substituting a fraction (x = 0?0.15) of the cationic element Sb. The CdxSb2?yS3?δ lattice expands relative to the host, Sb2S3, with its lattice constant a increasing linearly with Cd content x. Optical and external quantum efficiency (EQE) spectra revealed that the bandgap Eg of CdxSb2?yS3?δ decreased from 1.99 to 1.69 eV (i.e., 625?737 nm) as x increased from 0 to 0.15. Liquid-junction CdxSb2?yS3?δ quantum dot-sensitized solar cells were fabricated using the polyiodide electrolyte. The best cell yielded a power conversion efficiency (PCE) of 3.72% with the photovoltaic parameters of Jsc = 15.97 mA/cm2, Voc = 0.50 V, and FF = 46.6% under 1 sun. The PCE further increased to 4.86%, a respectable value for a new solar material, under a reduced light intensity of 10% sun. The PCE (4.86%) and Jsc (15.97 mA/cm2) are significantly larger than that (PCE = 1.8%, Jsc = 8.55 mA/cm2) of the Sb2S3 host. Electrochemical impedance spectroscopy showed that the ZnSe passivation coating increased the electron lifetime by three times. The EQE spectrum of CdxSb2?yS3?δ has a maximal EQE of 82% at λ = 350 nm and covers the spectral range of 300?750 nm, which is significantly broader than that (300?625 nm) of the Sb2S3 host. The EQE-integrated current density yields a Jph of 11.76 mA/cm2. The tunable bandgap and a respectable PCE near 5% suggest that CdxSb2?yS3?δ could be a potential candidate for a solar material.
关键词： ternary metal sulfide,CdxSb2?yS3?δ nanocrystals,photovoltaic performance,quantum dot-sensitized solar cells,bandgap tunable
更新于2025-09-12 10:27:22
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Facile synthesis of manganese (II)-doped ZnSe nanocrystals with controlled dimensionality
摘要： Doping is one of the key technologies in modern semiconductor science and industry. However, the synthetic control of doped nanocrystals is difficult to achieve. Here, we report the facile synthesis of manganese (II) doped ZnSe nanocrystals with controlled dimensionality. A strong Lewis acid-base reaction using air-stable and environmentally friendly metal chlorides as precursors can readily produce a large amount of quantum-confined ZnSe:Mn2+ nanocrystals. A combination of primary and secondary amines is used to control the synthetic chemistry, which enables the shape of the doped nanocrystals to be controlled. The final doping concentration of the products can be finely tunable, which is critical for carrier relaxation dynamics. It turns out that the threshold doping level for the maximum photoluminescence intensity of doped nanocrystals highly depends on their shape. Furthermore, this simple synthetic method is extendable to obtain various Mn2+-doped II–VI semiconductor nanocrystals such as CdS:Mn2+ and ZnS:Mn2+. Our study will facilitate the fundamental understanding of the doped semiconductor nanocrystals with different shapes, which is potentially useful for a wide range of applications such as lighting, photocatalysis, and bioimaging.
关键词： doping,quantum dots,ZnSe,nanocrystals,photoluminescence,Mn2+
更新于2025-09-12 10:27:22
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Controlled Surface for Enhanced Luminescence Quantum Yields of Silicon Nanocrystals; 蛍光シリコン粉末の機能増強を導く表面制御に関する研究;
摘要： In the current review paper, we provide the experimental evidences for the controlled structure of diamond cubic silicon nanocrystals (SiNCs) which enhances their photoluminescence quantum yields (PLQYs). Hydrogen-terminated Si provides a basic surface for further modification. Their enhancement was performed by a simple ligand exchange between the hydrogen atoms and hydrocarbon chains. On the basis of the systematic study on temperature dependence of PL properties along with relaxation dynamics, a long-accepted mechanism for enhancing absolute PL was recently revised. Specifically, combination of PL spectroscopic measurement from cryogenic to room temperature with structural characterization allows us to link the enhanced PLQYs with the notable difference in surface structure. The hydride-terminated surface suffers from the presence of a large amount of nonradiative relaxation channels whereas the passivation with alkyl monolayers suppresses the creation of the nonradiative relaxation channels to yield the high PLQY. This anchoring effect was responsible for the PLQYs as high as 56%. Tunability of PL bands was achieved in the wavelength ranging between 590 nm and 1064 nm. Next, the review considers the use of the highly emitting SiNCs for optoelectronic and biophotonic applications. The tunable light emitting diodes in which SiNCs serve as active layers are demonstrated. Si exhibits a high chemical affinity to covalent linkages with carbon, oxygen, and nitrogen, thereby producing almost unlimited variations in organic–Si architectures hybridized at the molecular level. Therefore, biomedical applications of SiNCs are attractive. Details of the biophotonic applications are not described in this review, but functional near-IR (NIR) emitting nanoparticles of SiNCs of narrow PL spectra having no long emission tails, continuously tunable over the 700–1000 nm window where the light absorption of water and the tissues including hemoglobin is minimal have a potential to become one of nontoxic biomarkers that is available in-vivo study. Finally, we provide perspective on the overall current status, challenges and potentials for this research field in near future.
关键词： Anchor effect,Silicon nanocrystals,Photoluminescence,Light emitting diode
更新于2025-09-12 10:27:22
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<i>In-situ</i> Biomineralization of Cu <sub/>x</sub> Zn <sub/>y</sub> Sn <sub/>z</sub> S <sub/>4</sub> Nanocrystals within TiO <sub/>2</sub> -based Quantum Dot Sensitized Solar Cell Anodes
摘要： CuZnSnS (CZTS) quantum dots (QDs) have potential application in quantum dot sensitized solar cells (QDSSCs); however, traditional synthesis approaches typically require elevated temperatures, expensive precursors, and organic solvents that can hinder large scale application. Herein we develop and utilize an enzymatic, aqueous phase, ambient temperature route to prepare CZTS nanocrystals with good compositional control. Nanoparticle synthesis occurs in a minimal buffered solution containing only the enzyme, metal chloride and acetate salts, and L-cysteine as a capping agent and sulfur source. Beyond isolated nanocrystal synthesis, we further demonstrate biomineralization of these particles within a preformed mesoporous TiO2 anode template where the formed nanocrystals bind to the TiO2 surface. This in-situ biomineralization approach facilitates enhanced distribution of the nanocrystals in the anode and, through this, enhanced QDSSC performance.
关键词： Copper Zinc Tin Sulfide,Quantum Dot Sensitized Solar Calls (QDSSC),Nanocrystals,Green Synthesis,Quantum Dots,Biomineralization
更新于2025-09-12 10:27:22