| 1. |
- Adranno, Brando, et al.
(författare)
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Broadband white-light-emitting electrochemical cells
- 2023
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Ingår i: Advanced Photonics Research. - : John Wiley & Sons. - 2699-9293. ; 4:5
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Tidskriftsartikel (refereegranskat)abstract
- Emerging organic light-emitting devices, such as light-emitting electrochemical cells (LECs), offer a multitude of advantages but currently suffer from that most efficient phosphorescent emitters are based on expensive and rare metals. Herein, it is demonstrated that a rare metal-free salt, bis(benzyltriphenylphosphonium)tetrabromidomanganate(II) ([Ph3PBn]2[MnBr4]), can function as the phosphorescent emitter in an LEC, and that a careful device design results in the fact that such a rare metal-free phosphorescent LEC delivers broadband white emission with a high color rendering index (CRI) of 89. It is further shown that broadband emission is effectuated by an electric-field-driven structural transformation of the original green-light emitter structure into a red-emitting structure.
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| 2. |
- Adranno, Brando, et al.
(författare)
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The 8-hydroxyquinolinium cation as a lead structure for efficient color-tunable ionic small molecule emitting materials
- 2023
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Ingår i: Advanced Photonics Research. - : John Wiley & Sons. - 2699-9293. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- Albeit tris(8-hydroxyquinolinato) aluminum (Alq3) and its derivatives are prominent emitter materials for organic lighting devices, and the optical transitions occur among ligand-centered states, the use of metal-free 8-hydroxyquinoline is impractical as it suffers from strong nonradiative quenching, mainly through fast proton transfer. Herein, it is shown that the problem of rapid proton exchange and vibration quenching of light emission can be overcome not only by complexation, but also by organization of the 8-hydroxyquinolinium cations into a solid rigid network with appropriate counter-anions (here bis(trifluoromethanesulfonyl)imide). The resulting structure is stiffened by secondary bonding interactions such as pi-stacking and hydrogen bonds, which efficiently block rapid proton transfer quenching and reduce vibrational deactivation. Additionally, the optical properties are tuned through methyl substitution from deep blue (455 nm) to blue-green (488 nm). Time-dependent density functional theory (TDFT) calculations reveal the emission to occur from which an unexpectedly long-lived S-1 level, unusual for organic fluorophores. All compounds show comparable, even superior photoluminescence compared to Alq3 and related materials, both as solids and thin films with quantum yields (QYs) up to 40-50%. In addition, all compounds show appreciable thermal stability with decomposition temperatures above 310 °C.
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| 3. |
- Andersson Ersman, Peter, et al.
(författare)
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Electrochromic Displays Screen Printed on Transparent Nanocellulose-Based Substrates
- 2023
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Ingår i: Advanced Photonics Research. - : John Wiley & Sons, Ltd. - 2699-9293.
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Tidskriftsartikel (refereegranskat)abstract
- Manufacturing of electronic devices via printing techniques is often considered to be an environmentally friendly approach, partially due to the efficient utilization of materials. Traditionally, printed electronic components (e.g., sensors, transistors, and displays) are relying on flexible substrates based on plastic materials; this is especially true in electronic display applications where, most of the times, a transparent carrier is required in order to enable presentation of the display content. However, plastic-based substrates are often ruled out in end user scenarios striving toward sustainability. Paper substrates based on ordinary cellulose fibers can potentially replace plastic substrates, but the opaqueness limits the range of applications where they can be used. Herein, electrochromic displays that are manufactured, via screen printing, directly on state-of-the-art fully transparent substrates based on nanocellulose are presented. Several different nanocellulose-based substrates, based on either nanofibrillated or nanocrystalline cellulose, are manufactured and evaluated as substrates for the manufacturing of electrochromic displays, and the optical and electrical switching performances of the resulting display devices are reported and compared. The reported devices do not require the use of metals and/or transparent conductive oxides, thereby providing a sustainable all-printed electrochromic display technology.
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| 4. |
- Delli Santi, Maria Giulia, et al.
(författare)
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Biogenic Fraction Determination in Fuel Blends by Laser-Based 14CO2 Detection
- 2021
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Ingår i: Advanced Photonics Research. - : John Wiley & Sons, Ltd. - 2699-9293. ; 2:3
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Tidskriftsartikel (refereegranskat)abstract
- A widespread use of biofuels is a key recommendation of the Paris Agreement and leading international organizations. It is an important step to mitigate the global warming effects due to greenhouse-gas emissions from fossil oils. To this aim, an analytical technique sufficiently cheap and compact, to foster its widespread adoption, is necessary. Herein, it is shown that a compact, laser-based spectrometer is suitable to replace the few established techniques, which have been used to quantify the biofraction in fuel blends, so far. Measurements of the biogenic fraction in different fuel samples are reported, with a precision of 1% in the whole range (0?100%) of possible blends, confirming a performance comparable to the best existing technique. An onsite-deployable saturated-absorption cavity ring-down (SCAR) spectrometer is used. The results demonstrate the potential of laser-based instrumentation to do the accurate and precise measurements required for the certification of biogenic content of any hydrocarbon-based material. Worldwide adoption of such laser-based technology for biofraction certification can significantly boost the market of biofuels and can prove to be a disruptive methodology for assessing the biogenic content in plastics and polymeric materials.
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| 5. |
- Hinrichs, Karsten, et al.
(författare)
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Field Manipulation of Band Properties in Infrared Spectra of Thin Films
- 2023
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Ingår i: ADVANCED PHOTONICS RESEARCH. - 2699-9293. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- This comprehensive optical study analyzes field manipulations of bands in infrared (IR) spectra of thin films and functional surfaces for varying measurement and sample conditions. Band variations related to the materials dielectric functions, the measurement geometry, the film thickness as well as the direction dependence of the probing electromagnetic fields are demonstrated. Examples are discussed for isotropic polymer films (approximate to 200 nm polymethylmethacrylate [PMMA]) on gold and silicon as well as an anisotropic hydrogen monolayer on a Si(111) surface, characterized by IR-attenuated total reflection, IR microscopy, and incidence-angle-dependent IR polarimetry. Even for fixed optical material properties, significant manipulations of band frequency and shape (shifts up to approximate to 14 cm-1 for PMMA, up to approximate to 3 cm-1 for H-Si) occur in not only polarization-dependent but also unpolarized spectra. The shown data underline that polarimetric measurements and optical analyses are essential for a detailed interpretation of band shapes. Field manipulations of bands in infrared spectra of thin films and functional surfaces are discussed. Examples are isotropic polymer films on gold and silicon as well as an anisotropic hydrogen monolayer on Si(111). Band variations relate to the materials dielectric functions, the measurement geometry, the film thickness as well as the polarization of the probing electromagnetic fields.image (c) 2023 WILEY-VCH GmbH
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| 6. |
- Mendoza-Galvan, Arturo, et al.
(författare)
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Modular Optical Diodes for Circular Polarization Based on Glass-Supported Cellulose Nanocrystal/Polyethylene Glycol Composite Films
- 2023
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Ingår i: ADVANCED PHOTONICS RESEARCH. - : WILEY. - 2699-9293.
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Tidskriftsartikel (refereegranskat)abstract
- Depending on processing methods and conditions, cellulose nanocrystal (CNC) films exhibit linear birefringence or selective Bragg reflection. The latter means reflection of light with left-handed circular polarization (LCP) due to CNC in a helicoidal microstructure of the same handedness. Herein, glass-supported CNC/polyethylene glycol (CNC/PEG) composite films with PEG concentrations in the range of 0-30% w/w with selective Bragg reflection at wavelengths from 440 to 550 nm are prepared. A modular device comprised of a dip-coated birefringent CNC-glass sample sandwiched between two CNC/PEG-glass samples shows different responses to light with LCP and to light with right-handed circular polarization (RCP). The device suppresses selective Bragg reflection from the rear (front) CNC/PEG sample for incident light with LCP (RCP), even when the birefringent film does not meet the condition for a halfwave plate. This behavior resembles the performance of optical diodes for circular polarization. Polarization properties of composite films and optical diodes in terms of degree of polarization and ellipticity are discussed within the Stokes-Mueller formalism. Electromagnetic simulations of Mueller matrices reveal the equivalence of modular and in-tandem film approaches of optical diodes. The handedness of circular polarization of light is reversed by a modular device comprised of a dip-coated birefringent cellulose nanocrystal (CNC) film sandwiched by two CNC/polyethylene glycol composite films. Asymmetric forward and backward propagation of circular propagation resembles an optical diode at wavelengths of selective Bragg reflection.image (c) 2023 WILEY-VCH GmbH
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| 7. |
- Pang, Jiu, 1992-, et al.
(författare)
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Light Propagation in Transparent Wood: Efficient Ray‐Tracing Simulation and Retrieving an Effective Refractive Index of Wood Scaffold
- 2021
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Ingår i: Advanced Photonics Research. - : Wiley. - 2699-9293 .- 2699-9293. ; 2:11, s. 2100135-2100135
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Tidskriftsartikel (refereegranskat)abstract
- Transparent wood (TW), a biocomposite material demonstrating optical transparency in the visible range, has attracted much interest in recent years due to great potential for ecofriendly applications, for instance, in construction industry and functionalized organic materials. Optical properties of TW, including transparency and haze, depend on a particular structure of cellulose-based backbone compound, (mis-)matching of the refractive indices (RIs) between TW compounds, and the polymer matrix. Although there are data of cellulose RIs for various forms of cellulose (fibers, powder, hot-pressed films, etc.), these values might differ from an effective RI of the TW substrate. Herein, a numerical model of light propagation in the TW, based on the real cellular structure in wood, is presented and applied to estimate an effective RI of the delignified wood reinforcement in the experimentally investigated TW material. Ray-tracing and rigorous electromagnetic approaches are compared for modeling light propagation in the TW. Ray tracing demonstrates considerably simplified yet accurate and efficient solutions. The work brings substantial progress toward realistic and practical wood modeling for the purpose of applications, materials design, and fundamental studies.
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| 8. |
- Rowan-Robinson, Richard M., et al.
(författare)
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Direction-Sensitive Magnetophotonic Surface Crystals
- 2021
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Ingår i: Advanced Photonics Research. - : John Wiley & Sons. - 2699-9293. ; 2:10
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Tidskriftsartikel (refereegranskat)abstract
- Nanometer-thin rare-earth-€“transition-metal (RE-€“TM) alloys with precisely controlled compositions and out-of-plane magnetic anisotropy are currently in the focus for ultrafast magnetophotonic applications. However, achieving lateral nanoscale dimensions, crucial for potential device downscaling, while maintaining designable optomagnetic functionality and out-of-plane magnetic anisotropy is extremely challenging. Herein, nanosized Tb18Co82 ferrimagnetic alloys, having strong out-of-plane magnetic anisotropy, within a gold plasmonic nanoantenna array to design a micrometer-scale magnetophotonic crystal that exhibits abrupt and narrow magneto-optical (MO) spectral features that are both magnetic field and light incidence direction controlled are integrated. The narrow Fano-type resonance arises through the interference of the individual nanoantenna’s surface plasmons and a Rayleigh anomaly of the whole nanoantenna array, in both optical and MO spectra, which are demonstrated and explained using Maxwell theory simulations. This robust magnetophotonic crystal opens the way for conceptually new high-resolution light incidence direction sensors, as well as for building blocks for plasmon-assisted all-optical magnetization switching in ferrimagnetic RE-€“TM alloys.
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| 9. |
- Shabani, Alireza, et al.
(författare)
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Revisiting the Optical Dispersion of Aluminum-Doped Zinc Oxide : New Perspectives for Plasmonics and Metamaterials
- 2021
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Ingår i: ADVANCED PHOTONICS RESEARCH. - : John Wiley & Sons. - 2699-9293. ; 2:4
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Tidskriftsartikel (refereegranskat)abstract
- Due to the high rate of optical losses and the extensive usage of noble metals, alternative plasmonic materials with maximum tunability and low loss are desired for future plasmonic and metamaterial devices and applications. Herein, the potential of aluminum-doped zinc oxide (AZO), one of the most prominent members of the transparent conducting oxide family, is demonstrated, for its applicability in plasmonic metamaterials. Using first-principles density functional theory, combined with optical calculations, AZO-based, plasmonic split-ring resonators (SRRs) as model examples are showcased. The results match with experimental reports for the optical dielectric functions of pure and 2.08% Al-doped zinc oxide (ZnO), if the Hubbard model to the local density approximation is applied. The broadband optical dispersion data for varying dopant concentrations (0%, 2.08%, and 6.25%) are extracted and provided. The subsequent optical response analyses show the existence of pronounced plasmons and inductor-capacitor modes in Al-doped ZnO SRRs and an enhancement in metallic characteristics and plasmonic performance of AZO upon increasing Al concentration. The findings predict AZO as a low-loss plasmonic material with promising capability for enhancing future optoelectronics applications. The method introduces a new, versatile approach to design future optical materials of arbitrary geometry.
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| 10. |
- Smirnov, Serguei, et al.
(författare)
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Sub‐THz Phase Shifters Enabled by Photoconductive Single‐Walled Carbon Nanotube Layers
- 2022
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Ingår i: Advanced Photonics Research. - : Wiley-VCH Verlagsgesellschaft. - 2699-9293 .- 2699-9293. ; , s. 2200042-2200042
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Tidskriftsartikel (refereegranskat)abstract
- Materials with tunable dielectric properties are highly relevant for terahertz (THz) applications. Herein, the tuning of the dielectric response of single-walled carbon nanotube layers by light illumination is studied for applications to THz phase shifters. The dependence of the length of individual nanotubes on the THz photoconductivity of the network is experimentally investigated in the frequency range of 0.2–1 THz by time-domain spectroscopy (TDS). The effective conductivity of the networks is described by a theoretical model that fits the measured dielectric function. Terahertz phase shifters are realized with the carbon nanotube layers as the optically tunable element deposited on the wall of rectangular dielectric waveguides. The phase of the electromagnetic wave propagating in the waveguide is shown to be tunable by illuminating the nanotubes. A linear phase shift with the frequency is measured between 75 and 500 GHz with a low change in amplitude due to the illumination.
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| 11. |
- Zeiske, Stefan, et al.
(författare)
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On the Impact of Cadmium Sulfide Layer Thickness on Kesterite Photodetector Performance
- 2023
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Ingår i: Advanced Photonics Research. - : Wiley-VCH Verlagsgesellschaft. - 2699-9293. ; 4:9
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Tidskriftsartikel (refereegranskat)abstract
- Kesterites are currently viewed as one of the most promising candidates for earth abundant and benign elements to substitute critical raw materials in photovoltaic technologies and may also be suitable for low-noise, room-temperature, self-powered photodetectors. However, while the impact of buffer layers on kesterite solar cell efficiency has been an active area of investigation, links between photodetector performance and intermediate layers are yet to be addressed. Herein, the impact of cadmium sulfide buffer layers on the performance of kesterite (Cu2ZnSnS4) photodetectors is probed. Specifically, the effect of buffer layer thickness on various photodetector performance metrices is clarified, including noise current, spectral responsivity, noise equivalent power, frequency response, and specific detectivity. Devices with a 100 nm cadmium sulfide layer perform the best, achieving a linear dynamic range of 180 dB and frequency responses in the range of tens of kHz. The key loss mechanisms are identified, and it is found that the photodetector performance to be primarily limited by shunt resistance-induced thermal noise and defect-induced nonradiative losses. Furthermore, we estimate the upper radiative limit of specific detectivity to be approximately 1019 Jones. Our results highlight the potential of kesterites to be used as an interesting earth abundant candidate for photodetection applications.
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