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Photo- and electroluminescence features of films and field effect transistors based on inorganic perovskite nanocrystals embedded in a polymer matrix
摘要： The optical and electrical properties of films and field-effect transistors (FETs) based on pure MEH-PPV, neat CsPbBr3 nanocrystals (NCs), and MEH-PPV:CsPbBr3 NCs composites with different contents of CsPbBr3 NCs are investigated. The films were characterized by absorbance, atomic-force microscope and current-voltage characteristics (I-Vs) techniques. Relative PL and EL intensities and PL spectra of the pure MEH-PPV, neat CsPbBr3 NCs and MEH-PPV:CsPbBr3 NCs films were measured at 300 K at various levels of optical and electrical excitation power; these dependencies of the PL and EL intensities turned out to be sublinear and superlinear respectively. FETs based on MEH-PPV:CsPbBr3 NCs (1:1) films exhibit I-Vs at 290 – 100 K a dominant hole transport mechanism. The mobility of charge carriers was determined at 290 K for neat CsPbBr3 NCs (for electrons: 2.7 10-2 cm2/Vs) and MEH-PPV:CsPbBr3 NCs (1:1) (for holes: 9 cm2/Vs). The temperature dependence of the hole mobility μFET(T) of FETs based on MEH-PPV:CsPbBr3 NCs (1:1) films characteristic of the hopping mode. It was found that the superlinearity of the dependence of EL of MEH-PPV:CsPbBr3 NCs LE-FETs at 290 K increases with increasing concentration of CsPbBr3 NCs due to efficient energy transfer between CsPbBr3 NCs and the MEH-PPV polymer matrix, and also because of the probability of electron tunneling through the potential barrier to electrode. It is expected that the obtained MEH-PPV:CsPbBr3 NCs nanocomposite films will be useful for efficient applications in nanotechnology LEDs, FETs and LE-FETs.
关键词： Energy transfer,Field-effect transistors,Semiconducting polymers,Photo- and electroluminescence,Charge carrier mobility,Inorganic perovskite nanocrystals
更新于2025-09-16 10:30:52
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Size-Dependent Photoresponse of Germanium Nanocrystals-Metal Oxide Semiconductor Photodetector
摘要： In this article, size-dependent photoresponse characteristics and low-frequency noise behavior of high-speed germanium nanocrystals (nc-Ge) photodetector have been reported. The nc-Ge embedded in SiO2 matrix with different sizes have been synthesized by annealing the cosputtered Ge-SiO2 thin films at 800 ?C–900 ?C. It has been observed that the photoresponse of the detector increases with the increasing size of nc-Ge. The sample annealed at 900 ?C showed maximum responsivity (3.5 A/W) with the fast response time. The low-frequency noise spectral power density in the current fluctuation (SI) have been measured for the fabricated nc-Ge photodetectors, and lowest noise equivalent power (NEP) and highest detectivity (D?) have been observed in the nc-Ge detector synthesized at 900 ?C. Tunable responsivity in nc-Ge has been observed due to size-dependent light absorption, electric field-driven carrier separation, and tunneling through the oxide barriers. The transient photoresponse behavior has also been studied and the best rise time of 6.2 μs was observed for nc-Ge synthesized at 900 ?C. These results suggest that the nc-Ge are a promising contender for high-performance integrated optoelectronic devices that are fully compatible with silicon technology in terms of fabrication and thermal budget.
关键词： Detectivity,noise equivalent power (NEP),responsivity,noise spectral power,germanium nanocrystals (nc-Ge)
更新于2025-09-16 10:30:52
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Three-Dimensional Laser-Assisted Patterning of Blue-Emissive Metal Halide Perovskite Nanocrystals inside a Glass with Switchable Photoluminescence
摘要： The high-precision patterning of metal halide perovskites (MHPs) is of paramount importance for their device application. Here, we demonstrate the femtosecond (fs)-laser-assisted formation of three-dimensional MHP nanocrystal (NC) patterns with strong blue photoluminescence (PL) inside an oxide glass. Our strategy enables the crystallization and erasing of CsPb(Cl/Br)3 NCs inside a glass localized around the laser focal area through a combination of fs laser irradiation and thermal treatment processes. These recoverable patterns exhibit a switchable PL associated with the laser-induced defect and the thermal healing of MHP NCs that are benefits from the soft ionic crystal structure and low formation energy of the MHPs. Due to the high stability offered by the protection of the oxide glass matrix, the laser printing of fine-structured MHP micropatterns can be repeated over multiple cycles with a high robustness compared with their colloidal process counterparts. Our results demonstrate a simple strategy for creating emissive patterns inside a stable and transparent solid matrix that could be promising for applications including information storage, three-dimensional displays, anticounterfeit labels, and information security protection.
关键词： three-dimensional patterning,perovskite nanocrystals,reversible photoluminescence,laser-assisted crystallization,femtosecond laser processing
更新于2025-09-16 10:30:52
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Ligand induced anomalous emission shift of size-controlled CsPbBr <sub/>3</sub> nanocrystals
摘要： CsPbX3 perovskite nanocrystals (NCs) have attracted much attention from researchers because of their excellent photoelectric properties like high quantum yield, large absorption cross section, and simple preparation process. The addition of ligands in the synthesis process has a significant effect on the microstructure and photophysical properties of solution-processed NCs, which needs further extensive studies. In this Letter, the effects of ligand electronegativity on the size and photoluminescence (PL) properties of CsPbBr3 NCs were reported. One is typical oleic acid with weak electronegativity, and another is 2-acrylamide-2-methylpropionic sulfonic acid with strong electronegativity. The third is their typical mixture with a molar ratio of 1:1. With the increase in ligand electronegativity, the size of CsPbBr3 NCs increases significantly. However, in contrast to the traditional quantum size confinement effect, the PL peak exhibits an abnormal blue shift gradually and the ligand passivation effect on NC surface defects also becomes more significant. The physical mechanism of this anomalous PL shift phenomena of CsPbBr3 NCs was investigated using the time-resolved PL spectrum and transient absorption spectrum.
关键词： transient absorption spectrum,quantum size confinement,photoluminescence,CsPbX3 perovskite nanocrystals,ligand electronegativity,time-resolved PL spectrum
更新于2025-09-16 10:30:52
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Modulation of Ligands Conjugation for Efficient FAPbBr3 based Green Light-Emitting Diodes
摘要： Organic ligands capped on surface of perovskite nanocrystals (PeNCs) strongly influence the optical and electrical properties of the obtained PeNCs films, which are fundamental for efficient perovskite light-emitting diodes (PeLEDs). Here, we investigate the ligands effect through introduction of ligands with strong π conjugation, 1-(1-naphthyl)ethylamine bromide (NEABr), for the fabrication of FAPbBr3 PeNCs. Compared to the widely applied ligands of phenylethylamine bromide (PEABr), NEABr molecules containing naphthalene ring possess more delocalized electrons and better conductivity, which is beneficial for charge injection and transportation between interfaces. By varying the ligands ratio, high quality three dimensional FAPbBr3 PeNCs films with photoluminescence quantum yields up to 80% are fabricated. Based on the optimized PeNCs films, electroluminescent (EL) devices achieve a maximum external quantum efficiency of 8.6%, which is about three times higher than that of EL devices based on PEABr. Importantly, through understanding into the ligands effect, we demonstrate that the enhanced device efficiency is attributed to lower defect densities and decreased interfacial resistance in NEABr derived EL devices. Our findings about ligands conjugation on device performance may benefit other perovskites based optoelectronic devices.
关键词： ligands conjugation,perovskite nanocrystals,light-emitting diodes,charge injection,FAPbBr3
更新于2025-09-16 10:30:52
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Heavily doped Semiconductor Colloidal Nanocrystals as Ultra-Broadband Switches for Near Infrared and Mid-Infrared Pulse Lasers
摘要： Heavily self-doped semiconductors can be designed to use for advanced photonics due to both fabrication and functional advantages. Ultrafast response, strong optical nonlinearity, broadband wavelength range and accessibility of integration are major challenges for ultrafast all-optical photonics operating in infrared wavelength range. Here, solution-processed Cu1.8Se semiconductor nanocrystals (NCs) demonstrate ultrafast response (about 360~520 fs), strong optical nonlinearity (as large as -1.4×103 cm GW-1) and broadband (from 800 to 3000 nm) nonlinear optical absorption in the near-infrared and mid-infrared wavelength range. The ultrafast response and larger optical nonlinearity may be triggered by the plasma ground-state bleaching in the strong surface electromagnetic filed. Stable Q-switched lasers in Er-doped fiber laser, Tm-doped fiber laser and Ho/Pr co-doped ZBLAN fiber laser are operated, respectively. These findings indicate that Cu1.8Se NCs are prospective nonlinear materials for ultrafast response and broadband pulse laser.
关键词： semiconductor nanocrystals,ultrafast photonics,optical modulation,superbroadband,nonlinear optical
更新于2025-09-16 10:30:52
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Direct Synthesis of Quaternary Alkylammonium Capped Perovskite Nanocrystals for Efficient Blue and Green Light-Emitting Diodes
摘要： Cesium lead halide nanocrystals (CsPbX3 NCs) are newcomer inorganic light sources covering the entire visible spectral range and exhibiting near-unity efficiencies. While the last years have seen rapid progress in green- and red-electroluminescence from CsPbX3 NCs, the development of blue counterparts remained rather stagnant. Controlling the surface state of CsPbX3 NCs had proven to be a major factor governing the efficiency of the charge injection and for diminishing the density of traps. Although didodecyldimethylammonium halides (DDAX, X=Br, Cl) had been known to improve the luminescence of CsPbX3 NCs when applied post-synthetically, they had not been used as a sole long-chain ammonium ligand directly in the synthesis of these NCs. Herein we report a facile, direct synthesis of DDAX-stabilized CsPbX3 NCs. We then demonstrate blue and green light-emitting diodes, characterized by the electroluminescence at 463-515 nm and external quantum efficiencies of 9.80% for green, 4.96% for sky-blue and 1.03% for deep-blue spectral regions.
关键词： Cesium lead halide nanocrystals,DDAX-stabilized,external quantum efficiencies,light-emitting diodes,electroluminescence
更新于2025-09-16 10:30:52
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Effect of incorporating different polyanilinea??surface modified nanosilica content into polyurethanea??based quasia??solida??state electrolyte for dyea??sensitized solar cells
摘要： Polyaniline-surface modified nanosilica (S-PANi) was incorporated into polyurethane (PU) to form a polymer matrix able to entrap liquid electrolyte and to function as a quasi-solid state electrolyte (QSE) in dye-sensitized solar cells (DSSCs). Nanosilica was first synthesized via sol–gel technique and was post modified with aniline to form S-PANi. The effects of introducing different S-PANi content (5, 10, 15, and 20 wt%) on the nanoparticle distribution, surface morphology, surface porosity, thermal stability, and the structure of the PU matrix were analyzed using transmitted and reflected light microscopes, TGA and X-ray powder diffraction. Additionally, polymer matrix absorptivity, conductivity, and ion diffusion of the formulated QSEs were investigated by using a digital analytical balance, the AC impedance method, and cyclic voltammetry. Lastly, all of the formulated quasi-solid-state electrolytes were applied for use in DSSCs wherein their charge recombination, photovoltaic performance, and lifespan were measured. The quasi-solid-state electrolyte based on 15 wt% S-PANi (PU-15%S-PANi) exhibited the highest light-to-energy conversion efficiency, namely 3.17%, with an open circuit voltage of 708 mV, a short circuit current of 4.13 mA cm?2, and a fill factor of 0.65.
关键词： films,swelling,nanoparticles,nanowires and nanocrystals,optical and photovoltaic applications,polyurethane
更新于2025-09-16 10:30:52
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Intrinsic exciton photophysics of PbS quantum dots revealed by low-temperature single nanocrystal spectroscopy
摘要： With a tunable size-dependent photoluminescence (PL) over a wide infrared wavelength range, lead chalcogenide quantum dots (QDs) have attracted significant scientific and technological interest. Nevertheless, the investigation of intrinsic exciton photophysics at the single-QD level has remained a challenge. Herein, we present a comprehensive study of PL properties for individual core/shell PbS/CdS QDs emissive near 1.0 eV. In contrast to the sub-meV spectral linewidths observed for II/VI QDs, PbS/CdS QDs are predicted to possess broad homogeneous linewidths. Performing spectroscopy at cryogenic (4 K) temperatures, we provide direct evidence confirming theoretical predictions, showing that intrinsic linewidths for PbS/CdS QDs are in the range of 8-25 meV, with an average of 16.4 meV. In addition, low-temperature, single-QD spectroscopy reveals a broad low-energy side emission attributable to optical as well as localized acoustic phonon-assisted transitions. By tracking single QDs from 4 K to 250 K we were able to probe temperature-dependent evolutions of emission energy, linewidth and line shape. Finally, polarization-resolved PL imaging showed that PbS/CdS QDs are characterized by a 3D emission dipole, in contrast with the 2D dipole observed for CdSe QDs.
关键词： PbS/CdS,bandgap,spectral linewidth,infrared nanocrystals,polarization,single nanocrystal spectroscopy
更新于2025-09-12 10:27:22
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Pink all-inorganic halide perovskite nanocrystals with adjustable characteristics: Fully reversible cation exchange, improving the stability of dopant emission and light-emitting diode application
摘要： In this work, we proposed a straightforward and effective strategy for preparing pink all-inorganic halide perovskite nanocrystal (NC) phosphors for light-emitting diode (LED) application. The pink perovskite NCs with varying Mn contents could be easily and steadily obtained via postsynthetic ion exchange at room temperature. The dependence of the size and optical properties of pink NCs on dopant content was systematically investigated. The reversible anion exchange processes of pink perovskite NCs were conducted with halide salts containing or excluding Pb. The contrasting results suggested that the irreversibility of Mn-emission was mainly affected by the fully reversible cation exchange between Pb2+ and Mn2+. The pink NCs with better stability of dopant emission and high monodispersity were successfully developed by compounding with silica. A pink LED was further made by using the pink NCs/silica composites as pink phosphors on a 395 nm InGaN LED chip. This work provides a feasible strategy for the fabrication of pink LEDs, which may have great application prospects in the field of special lighting, like neon lights and plant growth lights.
关键词： light-emitting diodes,anion exchange,perovskite nanocrystals,stability,cation exchange
更新于2025-09-12 10:27:22