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Converting an organic light-emitting diode from blue to white with Bragg modes
摘要： Organic light-emitting diodes (OLEDs) have been established as versatile light sources that allow for easy integration in large area surfaces and flexible substrates. In addition, the low fabrication cost of OLEDs renders them particularly attractive as general lighting sources. Current methods for the fabrication of white-light OLEDs rely on the combination of multiple organic emitters and/or the incorporation of multiple cavity modes in a thick active medium. These architectures introduce formidable challenges in both device design and performance improvements, namely the decrease of efficiency with increasing brightness (efficiency roll-off) and short operational lifetime. Here we demonstrate, for the first time, white light generation in an OLED consisting of a sub-100 nm-thick blue single emissive layer coupled to the photonic Bragg modes of a dielectric distributed Bragg reflector (DBR). We show that the Bragg modes, although primarily located inside the DBR stack, can significantly overlap with the emissive layer, thus efficiently enhancing emission and outcoupling of photons at selected wavelengths across the entire visible light spectrum. Moreover, we show that color temperature can be tuned by the DBR parameters, offering great versatility in the optimization of white-light emission spectra.
关键词： distributed Bragg reflector,white organic light-emitting diodes (WOLEDs),Fabry-Pérot modes,electroluminescence color conversion,organic semiconductors
更新于2025-09-19 17:13:59
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Dependence of material properties and photovoltaic performance of triple cation tin perovskites on the iodide to bromide ratio
摘要： In this work, the influence of a partial introduction of bromide (x = 0–0.33) into MA0.75FA0.15PEA0.1Sn(BrxI1?x)3 (MA: methylammonium, FA: formamidinium, PEA: phenylethylammonium) triple cation tin perovskite on the material properties and photovoltaic performance is investigated and characterized. The introduction of bromide shifts the optical band gap of the perovskite films from 1.29 eV for the iodide-based perovskite to 1.50 eV for the perovskite with a bromide content of x = 0.33. X-ray diffraction measurements reveal that the size of the unit cell is also gradually reduced based on the incorporation of bromide. Regarding the photovoltaic performance of the perovskite films, it is shown that already small amounts of bromide (x = 0.08) in the perovskite system increase the open circuit voltage, short circuit current density and fill factor. The maximum power conversion efficiency of 4.63% was obtained with a bromide content of x = 0.25, which can be ascribed to the formation of homogeneous thin films in combination with higher values of the open circuit voltage. Upon introduction of a higher amount of bromide (x = 0.33), the perovskite absorber layers form pinholes, thus reducing the overall device performance.
关键词： Semiconductors,Solar cell,Material science,Lead-free perovskite
更新于2025-09-19 17:13:59
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CdSe quantum dots-sensitized FRET system for ciprofloxacin detection
摘要： The prepared CdSe quantum dots (QDs) were applied to selectively and sensitively assay ciprofloxacin as a fluorescence sensor based on fluorescence resonance energy transfer (FRET) mechanism. The efficiency of FRET between CdSe QDs and ciprofloxacin can be modulated by the degree of spectral overlap between the excitation peak of CdSe QDs and the emission peak of ciprofloxacin. Within the range of 0 to 120 μmol·L?1, the good linearity was obtained (R = 0.99561) and the detection limit reached to 0.6 μmol·L?1. This method is simple and rapid and can be used in environmental water and milk samples.
关键词： Fluorescent sensor,Semiconductors,Luminescence,Ciprofloxacin,CdSe quantum dots,FRET
更新于2025-09-19 17:13:59
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Comparative Analysis of Injection Microdisk Lasers Based on InGaAsN Quantum Wells and InAs/InGaAs Quantum Dots
摘要： The results of comparative analysis of the spectral and threshold characteristics of room-temperature injection microdisk lasers of the spectral range 1.2×× μ m with different active regions, notably, InGaAsN/GaAs quantum wells or InAs/InGaAs/GaAs quantum dots are presented. It is found that microlasers of a comparable size with quantum wells possess a larger laser generation threshold when compared with microlasers with quantum dots. At the same time, the latter are characterized by a noticeably smaller fraction of emitted power corresponding to laser modes. The jump to lasing via an excited-state optical transition is also characteristic for them. Microdisk lasers based on InGaAsN alloy do not have these disadvantages.
关键词： nitrogen-containing semiconductors,quantum dots,quantum wells,microlaser
更新于2025-09-19 17:13:59
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Carbazole-Terminated Isomeric Hole-Transporting Materials for Perovskite Solar Cells
摘要： A set of novel hole-transporting materials (HTMs) based on π-extension through the carbazole units were designed and synthesized via a facile synthetic procedure. The impact of isomeric structural linking on their optical, thermal, electrophysical, and photovoltaic properties were thoroughly investigated combining experimental and simulation methods. Ionisation energies of HTMs were measured and are suitable with a triple-cation perovskite active layer ensuring efficient hole injection. New materials were successfully applied in perovskite solar cells (PSCs) and yielded a promising efficiency up to almost 18% under standard 100 mW cm-2 global AM1.5G illumination and show better stability tendency outperforming that of spiro-OMeTAD. This work provides guidance for the molecular design strategy of effective hole conducting materials for perovskite photovoltaics and similar electronic devices.
关键词： solar cell,carbazole,isomeric semiconductors,perovskite,hole transporting material
更新于2025-09-19 17:13:59
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Recent Progress on Near-Infrared Photoacoustic Imaging: Imaging Modality and Organic Semiconducting Agents
摘要： Over the past few decades, the photoacoustic (PA) effect has been widely investigated, opening up diverse applications, such as photoacoustic spectroscopy, estimation of chemical energies, or point-of-care detection. Notably, photoacoustic imaging (PAI) has also been developed and has recently received considerable attention in bio-related or clinical imaging fields, as it now facilitates an imaging platform in the near-infrared (NIR) region by taking advantage of the significant advancement of exogenous imaging agents. The NIR PAI platform now paves the way for high-resolution, deep-tissue imaging, which is imperative for contemporary theragnosis, a combination of precise diagnosis and well-timed therapy. This review reports the recent progress on NIR PAI modality, as well as semiconducting contrast agents, and outlines the trend in current NIR imaging and provides further direction for the prospective development of PAI systems.
关键词： photoacoustic imaging,near-infrared,contrast agents,organic semiconductors
更新于2025-09-19 17:13:59
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Tailoring of Bandgap to Tune the Optical Properties of Ga1?xAlxY (Y = As, Sb) for Solar Cell Applications by Density Functional Theory Approach
摘要： The bandgap was tuned to investigate the electronic and optical aspects using first-principle calculations for solar cells and other optical applications. The bandgap range varies from 1.6 to 2.1 eV for Ga1?xAlxAs and from 0.8 to 1.5 eV for Ga1?xAlxSb (x = 0.0, 0.25, 0.5, 0.75, 1.0). The dispersion, polarisation, and attenuation have been illustrated in terms of transparency and maximum absorption of light. The inversion of polarised atomic planes near the resonance allows the maximum absorption in ultraviolet to visible region. The Penn’s model (ε1(0) ≈ 1 + ((cid:126)ωp/Eg)2) and optical relation ε1(0) = n2(0) confirm the reliability of our finding. The maximum absorption, optical conduction, and minimum optical energy loss increase the credibility of the studied materials for energy storage device manufacture.
关键词： Bandgap Tune,Optical Properties,Semiconductors,Solar Cells Applications
更新于2025-09-19 17:13:59
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Extending the Photovoltaic Response of Perovskite Solar Cells into the Near‐Infrared with a Narrow‐Bandgap Organic Semiconductor
摘要： Typical lead-based perovskites solar cells show an onset of photogeneration around 800 nm, leaving plenty of spectral loss in the near-infrared (NIR). Extending light absorption beyond 800 nm into the NIR should increase photocurrent generation and further improve photovoltaic efficiency of perovskite solar cells (PSCs). Here, a simple and facile approach is reported to incorporate a NIR-chromophore that is also a Lewis-base into perovskite absorbers to broaden their photoresponse and increase their photovoltaic efficiency. Compared with pristine PSCs without such an organic chromophore, these solar cells generate photocurrent in the NIR beyond the band edge of the perovskite active layer alone. Given the Lewis-basic nature of the organic semiconductor, its addition to the photoactive layer also effectively passivates perovskite defects. These films thus exhibit significantly reduced trap densities, enhanced hole and electron mobilities, and suppressed illumination-induced ion migration. As a consequence, perovskite solar cells with organic chromophore exhibit an enhanced efficiency of 21.6%, and substantively improved operational stability under continuous one-sun illumination. The results demonstrate the potential generalizability of directly incorporating a multifunctional organic semiconductor that both extends light absorption and passivates surface traps in perovskite active layers to yield highly efficient and stable NIR-harvesting PSCs.
关键词： narrow-bandgap organic semiconductors,perovskite solar cells,NIR light harvesting,passivation
更新于2025-09-19 17:13:59
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One‐Pot Exfoliation of Graphitic C <sub/>3</sub> N <sub/>4</sub> Quantum Dots for Blue QLEDs by Methylamine Intercalation
摘要： Here, a simplified synthesis of graphitic carbon nitride quantum dots (g-C3N4-QDs) with improved solution and electroluminescent properties using a one-pot methylamine intercalation–stripping method (OMIM) to hydrothermally exfoliate QDs from bulk graphitic carbon nitride (g-C3N4) is presented. The quantum dots synthesized by this method retain the blue photoluminescence with extremely high fluorescent quantum yield (47.0%). As compared to previously reported quantum dots, the g-C3N4-QDs synthesized herein have lower polydispersity and improved solution stability due to high absolute zeta-potential (?41.23 mV), which combine to create a much more tractable material for solution processed thin film fabrication. Spin coating of these QDs yields uniform films with full coverage and low surface roughness ideal for quantum dot light-emitting diode (QLED) fabrication. When incorporated into a functional QLED with OMIM g-C3N4-QDs as the emitting layer, the LED demonstrates ≈60× higher luminance (605 vs 11 Cd m?2) at lower operating voltage (9 vs 21 V), as compared to the previously reported first generation g-C3N4 QLEDs, though further work is needed to improve device stability.
关键词： graphitic carbon nitride,quantum dot light-emitting diodes,metal-free semiconductors,hydrothermal exfoliation
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Evaluating the Electricity Production and Energy Saving from Transparent Photovoltaics for Windows in Commercial Buildings
摘要： A pentacene (C22H14)-based high-voltage organic thin-film transistor (HVOTFT) was demonstrated on both a rigid and a flexible substrate. The HVOTFT showed minimal degradation of the current–voltage (I–V ) characteristics under flexure. Consistent with the previous reports on amorphous silicon (a-Si) TFTs, the offset drain/source structure enabled high-voltage operation, allowing for the HVOTFT to switch very large drain-to-source voltages (VDS > 300 V) with a relatively lower controlling voltage (0 V < VG < 20 V). The HVOTFT was evaluated with three different gate insulators to assess how the dielectric constant and interface states influence device performance. Due to the high electric field generated in the device, the HVOTFT suffered from impeded charge injection into the gated semiconductor channel, similar to that reported in a-Si-based high-voltage TFTs, as well as from a nonsaturating I–V characteristic behavior similar to the short-channel effects found in FETs. A field plate was implemented to improve charge injection into the gated semiconductor channel. Output characteristics of the HVOTFT were numerically corrected to demonstrate that the device I–V can be modeled with the existing Si-based FET models.
关键词： Flexible substrates,high-κ gate dielectrics,organic thin-film transistors (HVTFTs),high-voltage semiconductors
更新于2025-09-19 17:13:59