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Liquefied petroleum gas sensing properties of ZnO/PPy/PbS QDs nanocomposite prepared by self-assembly combining with SILAR method
摘要： In this paper, a high-performance liquefied petroleum gas (LPG) sensor based on zinc oxide/polypyrrole/lead sulfide quantum dots (ZnO/PPy/PbS QDs) nanocomposite film was demonstrated, which was fabricated by layer-by-layer (LbL) self-assembly and successive ionic layer adsorption and reaction (SILAR) technique. The nanostructure features of the as-prepared ZnO/PPy/PbS nanocomposite film were confirmed by various characterization techniques. The room temperature gas-sensing investigation of the ZnO/PPy/PbS QDs nanocomposite sensor was performed against LPG gas in a wide concentration range. The experimental results showed an outstanding response for LPG sensing at room temperature compared with previous reports, the response can reach 45.47% at 1000 ppm LPG. And it also demonstrated good selectivity and excellent repeatability. The sensing mechanism of the PPy/ZnO/PbS QDs nanocomposite film gas sensor is owing to the p-n heterojunction created at the ZnO/PPy interface, as well as much more active adsorption sites.
关键词： polypyrrole,liquefied petroleum gas,zinc oxide,lead sulfide quantum dots,SILAR method
更新于2025-11-14 17:04:02
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Oxygen Plasma-Induced p-type Doping Improves Performance and Stability of PbS Quantum Dot Solar Cells
摘要： PbS quantum dots (QDs) have been extensively studied for photovoltaic applications thanks to their facile and low-cost fabrication processing and interesting physical properties such as size-dependent and tunable bandgap. However, the performance of PbS QDs based solar cells is highly sensitive to the humidity level in the ambient air, which is a serious obstacle toward its practical applications. Although it has been previously revealed that oxygen doping of the hole transporting layer (HTL) can mitigate the cause of this issue, the suggested methods to recover the device performance are time-consuming and relatively costly. Here, we report on a low-power oxygen plasma treatment as a rapid and cost-effective method to effectively recover the device performance and stability. Our optimization results show that a 10 min treatment is the best condition, resulting in an enhanced power conversion efficiency (PCE) from 6.9% for the as-prepared device to 9% for the plasma treated one. Moreover, our modified device shows long-term shelf-life stability.
关键词： colloidal quantum dots,plasma,lead sulfide,photovoltaics,stability
更新于2025-10-22 19:40:53
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Robust Polymer Matrix Based on Isobutylene (Co)Polymers for Efficient Encapsulation of Colloidal Semiconductor Nanocrystals
摘要： We introduce new oxygen- and moisture-proof polymer matrices based on polyisobutylene (PIB) and its block copolymer with styrene (poly(styrene-block-isobutylene-block-styrene), PSt-b-PIB-b-PSt) for encapsulation of colloidal semiconductor nanocrystals. In order to prepare transparent and processable composites, we developed a special procedure of the nanocrystal surface engineering including ligand exchange of parental organic ligands to inorganic species followed by attachment of specially designed short-chain PIB functionalized with amino-group (PIB-NH2). The latter provides excellent compatibility of the particles with the polymer matrices. As colloidal nanocrystals, we chose CdSe nanoplatelets (NPLs), since they possess a large surface and thus are very sensitive to the environment, in particular in terms of their limited photostability. The encapsulation strategy is quite general and can be applied to a wide variety of semiconductor nanocrystals, as demonstrated on the example of PbS quantum dots. All obtained composites exhibited excellent photostability being tested in a focus of a powerful white-light source, as well as exceptional chemical stability in a strongly acidic media. We compared these properties of the new composites with those of widely used polyacrylate based materials, demonstrating the superiority of the former. The developed composites are of particular interest for application in optoelectronic devices, such as color-conversion light emitting diodes (LEDs), laser diodes, luminescent solar concentrators, etc.
关键词： photoluminescence,nanocrystals-in-polymer composites,lead sulfide quantum dots,semiconductor nanocrystals,isobutylene (co)polymers,cadmium selenide nanoplatelets,photostability,chemical stability
更新于2025-09-19 17:15:36
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Lead Sulfide Saturable Absorber Based Passively Mode-locked Tm-doped Fiber Laser
摘要： In this paper, a passively mode-locked Tm-doped fiber laser by employing lead sulfide (PbS) nanoparticles as the saturable absorber (SA) is successfully demonstrated in the 2 μm region for the first time, to the best of our knowledge. Measured by a home-made balanced twin-detector setup at 2 μm, the PbS SA was characterized by the modulation depth of 10.69%, the non-saturable loss of 74.27%, and the saturable peak intensity of 8.62 MW/cm2, respectively. The laser delivered stable conventional soliton with a pulse duration of 1.24 ps and a repetition rate of 21.93 MHz. The center wavelength and 3 dB bandwidth are 1957.37 nm and 3.43 nm, respectively. Additionally, the second-order harmonic soliton pulses with a repetition rate of 43.86 MHz were also observed by further increasing the pump power. Our work reveals that PbS material is a reliable SA applied for pulse generation in the 2 μm spectral region.
关键词： saturable absorber,mode-locking,lead sulfide,Tm-doped fiber laser
更新于2025-09-16 10:30:52
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Optical Properties, Morphology, and Stability of Iodide-Passivated Lead Sulfide Quantum Dots
摘要： Iodide atomic surface passivation of lead chalcogenides has spawned a race in efficiency of quantum dot (QD)-based optoelectronic devices. Further development of QD applications requires a deeper understanding of the passivation mechanisms. In the first part of the current study, we compare optics and electrophysical properties of lead sulfide (PbS) QDs with iodine ligands, obtained from different iodine sources. Methylammonium iodide (MAI), lead iodide (PbI2), and tetrabutylammonium iodide (TBAI) were used as iodine precursors. Using ultraviolet photoelectron spectroscopy, we show that different iodide sources change the QD HOMO/LUMO levels, allowing their fine tuning. AFM measurements suggest that colloidally-passivated QDs result in formation of more uniform thin films in one-step deposition. The second part of this paper is devoted to the PbS QDs with colloidally-exchanged shells (i.e., made from MAI and PbI2). We especially focus on QD optical properties and their stability during storage in ambient conditions. Colloidal lead iodide treatment is found to reduce the QD film resistivity and improve photoluminescence quantum yield (PLQY). At the same time stability of such QDs is reduced. MAI-treated QDs are found to be more stable in the ambient conditions but tend to agglomerate, which leads to undesirable changes in their optics.
关键词： quantum dots,iodide,stability,lead sulfide,ligand exchange
更新于2025-09-16 10:30:52
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Spray coated PbS nano-crystals as an effective counter-electrode material for platinum free Dye-Sensitized Solar Cells (DSSCs)
摘要： This work aims to replace the expansive counter electrode material such as Platinum with low-cost lead sulfide (PbS). Here, lead xanthate was used as a precursor material to synthesize PbS. The precursor material of different concentrations were spray coated on conductive glass substrates and then heated in air at different temperatures and time intervals. The cubical crystals of PbS were formed when heated at 120 °C for 2 h. Field emission scanning electron microscopy (FESEM) and X-ray powder diffraction (XRD) analyses were conducted to substantiate the PbS nanocrystals free of any precursor materials. Cyclic Voltammetry (CV) was performed to inspect the electrochemical performance of PbS crystals. The results found here show that PbS as a catalyst material shows good catalytic activity at the counter electrode of dye-sensitized solar cells (DSSCs). Under optimal conditions, DSSC with PbS shows the power-conversion-efficiency (PCE) of 4.71%, which is slightly lower than that of Pt-based device (5.34%), fabricated under similar conditions.
关键词： Photosensitized,Catalyst,Electrochemical,Photovoltaic,Lead sulfide
更新于2025-09-16 10:30:52
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Carrier Multiplication in PbS Quantum Dots Anchored on a Au Tip using Conductive Atomic Force Microscopy
摘要： Carrier multiplication (CM) is the amplification of the excited carrier density by two times or more when the incident photon energy is larger than twice the bandgap of semiconductors. A practical approach to demonstrate the CM involves the direct measurement of photocurrent in the device. Specifically, photocurrent measurement in quantum dots (QDs) is typically limited by high contact resistance and long carrier-transfer length, which yields a low CM conversion efficiency and high CM threshold energy. Here, the local photocurrent is measured to evaluate the CM quantum efficiency from a QD-attached Au tip of a conductive atomic force microscope (CAFM) system. The photocurrent is efficiently measured between the PbS QDs anchored on a Au tip and a graphene layer on a SiO2/Si substrate as a counter electrode, yielding an extremely short channel length that reduces the contact resistance. The quantum efficiency extracted from the local photocurrent data with an incident photon energy exhibits a step-like behavior. More importantly, the CM threshold energy is as low as twice the bandgap, which is the lowest threshold energy of optically observed QDs to date. This enables the CAFM-based photocurrent technique to directly evaluate the CM conversion efficiency in low-dimensional materials.
关键词： lead sulfide quantum dots,conductive atomic force microscopy,carrier multiplication,photocurrent measurement
更新于2025-09-16 10:30:52
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Photophysical and electronic properties of bismuth-perovskite shelled lead sulfide quantum dots
摘要： Metal halide perovskite shelled quantum dot solids have recently emerged as an interesting class of solution-processable materials that possess the desirable electronic properties of both quantum dots and perovskites. Recent reports have shown that lead sulfide quantum dots (PbS QDs) with perovskite ligand-shells can be successfully utilized in (opto)electronic devices such as solar cells, photoconductors, and field-effect transistors (FETs), a development attributed to the compatibility of lattice parameters between PbS and certain metal halide perovskites that results in the growth of the perovskite shell on the PbS QDs. Of several possible perovskite combinations used with PbS QDs, bismuth-based variants have been shown to have the lowest lattice mismatch and to display excellent performance in photoconductors. However, they also display photoluminescence (PL), which is highly sensitive to surface defects. In this work, we present an investigation of the transport and optical properties of two types of bismuth-based perovskite (MA3BiI6 and MA3Bi2I9) shelled PbS QDs. Our photophysical study using temperature-dependent PL spectroscopy between 5 and 290 K indicates that the PL efficiency of the reference oleic acid (OA) capped samples is much higher than that of the Bi-shelled ones, which suffer from traps, most likely formed at their surfaces during the phase-transfer ligand exchange process. Nevertheless, the results from electrical measurements on FETs show the successful removal of the native-OA ligands, displaying electron dominated transport with modest mobilities of around 10?3 cm2 [V s]?1 – comparable to the reported values for epitaxial Pb-based shelled samples. These findings advance our understanding of perovskite shelled QD-solids and point to the utility of these Bi-based variants as contenders for photovoltaic and other optoelectronic applications.
关键词： field-effect transistors,bismuth-perovskite,electronic properties,photoluminescence,photophysical properties,lead sulfide quantum dots
更新于2025-09-12 10:27:22
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Simple Synthesis Method and Characterizations of Aggregation-Free Cysteamine Capped PbS Quantum Dot
摘要： Quantum dots have diverse chemical properties with di?erent ligands attached on the surface. The cysteamine has been used as a ligand for various quantum dots because it has high solubility in water, and it facilitates binding of quantum dot and gold surface. However, the hydrogen bonds in cysteamine cause aggregation of the cysteamine capped quantum dots. In this study, we suggested a simple synthesis method of aggregation-free PbS quantum dot and analyzed the electric and optical properties of the synthesized quantum dot. This study on aggregation-free cysteamine capped quantum dots has the potential to develop advanced quantum dot-based sensor technologies, including biomedical imaging and environmental sensors.
关键词： aggregation-free,cysteamine capped quantum dots,lead sulfide quantum dots,water-soluble quantum dots
更新于2025-09-12 10:27:22
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Photovoltaic and photoconductive action due to PbS quantum dots on graphene/SiC Schottky diodes from NIR to UV
摘要： We demonstrate photovoltaic and photoconductive responses to near-infrared light in devices formed by depositing a film of gel permeation chromatography purified PbS quantum dots (QDs) on top of n-SiC epitaxial layers with natively grown, low-leakage 10-15 monolayer thick epitaxial graphene (EG) Schottky contacts. The QD-film layer was removable by selective chemical etching, resetting the EG/SiC Schottky diode: sub-bandgap response could be restored in subsequent PbS-QD depositions. The EG in these devices simultaneously forms Schottky contacts to SiC and ohmic contacts to PbS-QD, enabling electrical screening and isolation of these interfaces from each other. After PbS-QD deposition, the diodes exhibit photovoltaic and photoconductive response at photon energies far below the SiC bandgap, extending to the NIR gap of the QD film. Scanning photocurrent microscopy illustrates that this is due to charge transfer from the QD-film to the n-type 4H-SiC through a trap-limited, rectifying PbS-QD/SiC heterojunction with ideality n=2 in parallel with the EG/SiC Schottky diode. The photoconductive gain at this QD/SiC interface could be useful for IR detection in wide bandgap platforms. Response times as fast as 40 ms are suitable for imaging applications, although careful contact design is required to optimize work-function matching and spreading resistance.
关键词： scanning photocurrent microscopy,Quantum dot,photovoltaic,GPC,silicon carbide,lead sulfide
更新于2025-09-12 10:27:22