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Spectroscopic and luminescence properties of Ho3+ ions doped Barium Lead Alumino Fluoro Borate glasses for green laser applications
摘要： Optically transparent Barium Lead Alumino Fluoro Borate (BaPbAlFB) glasses doped with different concentrations of Ho3+ ions were prepared by using melt quench technique. Raman spectral studies were conducted to understand the structural groups present in the as prepared glasses at room temperature. Spectroscopic investigations such as optical absorption, excitation, emission and decay measurements were conducted to understand the visible photoluminescence (PL) and lasing potentialities of BaPbAlFB glasses. The bonding parameters (δ) estimated from the absorption spectral features were used to understand the nature of bonding between Ho3+ ions and the surrounding ligands. The Urbach energy values estimated from the absorption spectral data are used to verify the amorphous nature of the present glass system. The Judd-Ofelt (J-O) theory has been applied to the measured oscillator strengths of the absorption spectral features to estimate the best fit J-O parameters (?λ, λ= 2, 4, and 6) useful in evaluating various radiative parameters for the prominent fluorescent levels of Ho3+ ions in BaPbAlFB glasses. The experimental lifetimes (τexp) are found to be decreasing with increase in Ho3+ ion concentration owing to energy transfer. The quantum efficiency (η) of Ho3+ ions doped BaPbAlFB glasses were estimated by correlating the experimental lifetimes (τexp) with the radiative lifetimes (τR). The strong visible emission, large stimulated emission cross-section (σse), high branching ratio (βR) and relatively good quantum efficiency (η) obtained for 5S2→ 5I8 (green) transition of 1mol% of Ho3+ ions doped BaPbAlFB glass reveals its suitability in designing and developing visible green lasers.
关键词： emission cross-sections,Holmium,glasses,quantum efficiency,CIE coordinates,photoluminescence
更新于2025-09-19 17:13:59
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Wafer-size growth of 2D layered SnSe films for UV-Visible-NIR Photodetector Arrays with High Responsitivity
摘要： Due to its excellent electrical and optical property, tin selenide (SnSe), a typical candidate of two-dimentional (2D) semiconductors, has attracted great attention in the field of novel optoelectronics. However, the large-area growth of high-quality SnSe films still remain a great challenge which limit its practical applications. Here, wafer-size SnSe ultrathin films with high uniformity and crystallization are deposited via a scalable magnetron sputtering method. The results show that the SnSe photodetector is highly sensitive to a broad wavelength in the UV-Visible-NIR range, especially showing an extremely high responsivity of 277.3 A W -1 with the corresponding external quantum efficiency of 8.5×104% and detectivity of 7.6×1011 Jones. These figures-of-merits are among the best performance for the sputter-fabricated 2D photodetector devices. The photodetecting mechanisms based on a photogating effect induced by the trapping effect of the localized defects are discussed in details. The results indicate that the few-layered SnSe films from the sputtering growth would have great potential in designing high-performance photodetector arrays.
关键词： tin selenide,detectivity,responsivity,optoelectronics,SnSe,UV-Visible-NIR,2D semiconductors,external quantum efficiency,photodetector,magnetron sputtering
更新于2025-09-19 17:13:59
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Effect of Temperature on the Characteristics of 4H-SiC UV Photodetectors
摘要： The influence exerted by the carrier concentration in the range (1–50) × 1014 cm–3 in n-4H-SiC chemical-vapor deposited (CVD) epitaxial layers on the spectral characteristics of UV photodetectors with Cr Schottky barriers in the range of 200–400 nm is revealed and explained in terms of the photoconductivity theory. Schottky barriers with a Cr film thickness of 20 nm and diameter of 8 mm are formed by thermal evaporation in vacuum through masks. A noticeable effect of the carrier concentration in the CVD epitaxial layers on the spectral characteristics of photodetectors upon heating to 200°C is also observed and accounted for by a difference between the generation-recombination processes. The irradiation of photodetectors with 15-MeV protons at a fluence of 4 × 1012 cm–2 and a temperature of 200°C leads to an increase in the quantum efficiency as compared to samples irradiated in similar modes at 25°C. This is indicative of an increase in the radiation hardness and service life of 4H-SiC devices at elevated temperatures.
关键词： irradiation,quantum efficiency,protons,silicon carbide,fluence
更新于2025-09-19 17:13:59
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A remarkable effect of Pr doping on key optoelectrical properties of CdS thin films prepared using spray pyrolysis technique for high-performance photodetector applications
摘要： High-quality thin film-based photodetectors containing praseodymium doped cadmium sulfide (Pr:CdS) were fabricated through spray pyrolysis and studied for various opto-electrical applications. Field emission electron microscopy (FE-SEM) revealed that the prepared films were highly compacted with an extremely fine nanostructure without any pinhole or crack. X-ray diffraction and FT-Raman spectroscopy studies confirmed the single hexagonal phase of all the films. The crystallite size was found to lie between 19 and 32 nm. Optical spectroscopy revealed that the fabricated films have low absorbance and high transmittance (in range of 70–80%). The energy gap was found to lie in the range of 2.40–2.44 eV. The PL spectra contained an intense green emission band at ~531 ± 5 nm (2.33 eV), and its intensity was enhanced by increasing the Pr doping content in CdS. The dark and photo currents of CdS increased by approximately 950 and 42 times, respectively with the addition of 5.0 wt.% Pr. The responsivity (R) and specific detectivity (D*) were remarkably enhanced to 2.71 AW-1 and 6.9×1011 Jones, respectively, for the 5.0 wt.% Pr:CdS film. The external quantum efficiency (EQE) of 5 wt.% Pr:CdS films was 43 times that of pure CdS films, and the on/off ratio was 3.95 × 102 for 5.0 wt.% Pr:CdS film. Its high R, D*, and EQE values, and photo-switching behavior make Pr:CdS a good contender for high quality photodetector applications.
关键词： responsivity,external quantum efficiency,detectivity,CdS and Pr: CdS films,opto-electrical properties
更新于2025-09-19 17:13:59
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Cu( <scp>i</scp> )a??I coordination polymers as the possible substitutes of lanthanides as downshifters for increasing the conversion efficiency of solar cells
摘要： This study tries to provide new solutions to increase the e?ciency of conversion of photons in solar cells, using photoluminescent Cu(I) coordination polymers (CPs) as possible alternative materials of lower cost, than those used today, based on lanthanides. The selected CP of chemical formula [Cu(NH2MeIN)I]n (NH2MeIN = methyl, 2-amino isonicotinate) absorbs in the utraviolet and emits in the visible region, being also easily nanoprocessable, by a simple and one-pot bottom-up approach. Nano?bers of this CP can be embedded in organic matrices such as ethyl vinyl acetate (EVA), forming transparent and homogenous ?lms, with a thermal stability of up to approximately 150 °C. These new materials maintain the optical pro-perties of the CP used as a dopant, ([Cu(NH2MeIN)I]n), with emission in yellow (570 nm) at 300 K, which is intensi?ed when the working temperature is lowered. In addition, these materials can be prepared with varying thicknesses, from a few microns to a few hundred nanometers, depending on the deposition method used (drop casting or spin coating respectively). The study of their external quantum e?ciency (EQE) found an increase in the UV range, which translates into an increase in the conversion e?ciency. The optimal CP concentration is 5% by weight in order to not diminish the transparency of the composite material. The calculated cost on the possible incorporation of this material into solar cells shows a 50% decrease over the cost reported in similar studies based on the use of lanthanides.
关键词： EVA,photoluminescent,Cu(I) coordination polymers,solar cells,downshifters,external quantum efficiency
更新于2025-09-19 17:13:59
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Perovskite-molecule composite thin films for efficient and stable light-emitting diodes
摘要： Although perovskite light-emitting diodes (PeLEDs) have recently experienced significant progress, there are only scattered reports of PeLEDs with both high efficiency and long operational stability, calling for additional strategies to address this challenge. Here, we develop perovskite-molecule composite thin films for efficient and stable PeLEDs. The perovskite-molecule composite thin films consist of in-situ formed high-quality perovskite nanocrystals embedded in the electron-transport molecular matrix, which controls nucleation process of perovskites, leading to PeLEDs with a peak external quantum efficiency of 17.3% and half-lifetime of approximately 100 h. In addition, we find that the device degradation mechanism at high driving voltages is different from that at low driving voltages. This work provides an effective strategy and deep understanding for achieving efficient and stable PeLEDs from both material and device perspectives.
关键词： perovskite light-emitting diodes,external quantum efficiency,perovskite-molecule composite thin films,operational stability
更新于2025-09-19 17:13:59
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Effect of a p-type ZnO insertion layer on the external quantum efficiency of GaInN light-emitting diodes
摘要： The external quantum ef?ciency (EQE) of a GaInN green light-emitting diode (LED) is improved by inserting a p-type ZnO layer between the indium tin oxide electrode and the p-type GaN layer. Several hypotheses are discussed to explain the EQE improvement in the LED with the ZnO layer. It is concluded that higher hole injection ef?ciency and better electron con?nement explain the EQE improvement, which is supported by the results of device simulations showing that the EQE is sensitive to the polarization sheet charge density at the interface between the last quantum barrier and electron-blocking layer.
关键词： external quantum efficiency,electron confinement,GaInN,hole injection efficiency,light-emitting diodes,p-type ZnO
更新于2025-09-16 10:30:52
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Improving the performance of light-emitting diodes via plasmonic-based strategies
摘要： Light-emitting diodes (LEDs), featuring long lifetime, small size, and low energy consumption, are increasingly popular for displays and general light sources. In the past decades, new light-emitting materials and novel device configurations are being continuously investigated to obtain highly efficient LEDs. Nevertheless, the unsatisfying external quantum efficiency severely limits their commercial implementation. Among all the approaches to boost the efficiency of LEDs, the incorporation of plasmonic structures exhibits great potential in increasing the spontaneous emission rates of emitters and improving the light extraction efficiency. In this Perspective, the methods to deal with challenges in quantum-well-based LEDs and organic LEDs by employing plasmonic materials are described, the mechanisms of plasmonic-based strategies to improve the light generation and extraction efficiency are discussed, and the plasmonic control over directional emission of phosphors is introduced as well. Moreover, important issues pertaining to the design, fabrication, and manipulation of plasmonic structures in LEDs to optimize the device performance, as well as the selection roles in finding appropriate plasmonic materials and structures for desired LED devices, are explained. This perspective lists the challenges and opportunities of plasmonic LEDs, with the aim of providing some insights into the future trends of plasmonic LEDs.
关键词： spontaneous emission rates,light-emitting diodes,light extraction efficiency,external quantum efficiency,plasmonic structures
更新于2025-09-16 10:30:52
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Photophysics and electroluminescence of red quantum dots diluted in a thermally activated delayed fluorescence host
摘要： A feasible, universal, and low-cost strategy for quantum dot light-emitting devices (QLEDs) was provided to significantly enhance the electroluminescent performances. The emissive layer consists of organic host materials and quantum dots (QDs), and then the efficient energy transfer process remarkably promotes the device performances. It is confirmed that a highly efficient QLED can be realized by a host–guest system without common hole transport layers. The red device based on the thermally activated delayed fluorescence host and QD guest achieved a peak external quantum efficiency of 7.4%. Further, by simply modifying PEDOT:PSS with poly(4-styrenesulfonic acid), the work-function can be easily elevated, accompanied with the boosted external quantum efficiency to 11.9%. It is believed that such performances originate simultaneously from reduced interfacial fluorescence quenching, elevated work-function and efficient F?rster resonance energy transfer in the host–guest system.
关键词： external quantum efficiency,electroluminescent performances,quantum dot light-emitting devices,QLEDs,thermally activated delayed fluorescence,F?rster resonance energy transfer,host–guest system
更新于2025-09-16 10:30:52
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High efficient light-emitting diodes with improved the balance of electron and hole transfer via optimizing quantum dot structure
摘要： Modifying the structure of quantum dots (QDs) is regarded as one of the promising way to improve the charge transfer balance of quantum dot light-emitting diodes (QLEDs). In this paper, we report highly bright Cd0.1Zn0.9S/CdSe/CdS quantum dots by optimizing the CdSe shell and CdS outer shell and explore their application in QLEDs. We ?nd that with appropriate thicknesses of CdSe and CdS shell the charge transfer balance of the device can be improved. Comparable studies on two red QLEDs with Cd0.1Zn0.9S/CdSe/CdS and CdSe/CdS show that the external quantum e?ciency (EQE) of the Cd0.1Zn0.9S/CdSe/CdS device is over 3 folds higher than its counterpart, implying that structure of the QDs plays an important role in controlling the charge transfer balance of the QLEDs.
关键词： quantum dots,external quantum efficiency,QLEDs,charge transfer balance,Cd0.1Zn0.9S/CdSe/CdS
更新于2025-09-16 10:30:52