The Experts below are selected from a list of 2928 Experts worldwide ranked by ideXlab platform
Hiroaki Jinno - One of the best experts on this subject based on the ideXlab platform.
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self powered ultraflexible photonic skin for continuous bio signal detection via air operation stable Polymer light emitting Diodes
Nature Communications, 2020Co-Authors: Kenjiro Fukuda, Tomoyuki Yokota, Hiroaki Jinno, Mari Koizumi, Wakako Yukita, Masahiko Saito, Itaru Osaka, Takao SomeyaAbstract:Ultraflexible optical devices have been used extensively in next-generation wearable electronics owing to their excellent conformability to human skins. Long-term health monitoring also requires the integration of ultraflexible optical devices with an energy-harvesting power source; to make devices self-powered. However, system-level integration of ultraflexible optical sensors with power sources is challenging because of insufficient air operational stability of ultraflexible Polymer Light-Emitting Diodes. Here we develop an ultraflexible self-powered organic optical system for photoplethysmogram monitoring by combining air-operation-stable Polymer Light-Emitting Diodes, organic solar cells, and organic photodetectors. Adopting an inverted structure and a doped polyethylenimine ethoxylated layer, ultraflexible Polymer Light-Emitting Diodes retain 70% of the initial luminance even after 11.3 h of operation under air. Also, integrated optical sensors exhibit a high linearity with the light intensity exponent of 0.98 by Polymer Light-Emitting Diode. Such self-powered, ultraflexible photoplethysmogram sensors perform monitoring of blood pulse signals as 77 beats per minute. Flexible electronic devices remain an attractive technology for optical sensor applications that require long-term health monitoring and conformability on human skin. Here, the authors report an ultrathin self-powered integrated organic optical system for plethysmogram monitoring.
Takao Someya - One of the best experts on this subject based on the ideXlab platform.
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self powered ultraflexible photonic skin for continuous bio signal detection via air operation stable Polymer light emitting Diodes
Nature Communications, 2020Co-Authors: Kenjiro Fukuda, Tomoyuki Yokota, Hiroaki Jinno, Mari Koizumi, Wakako Yukita, Masahiko Saito, Itaru Osaka, Takao SomeyaAbstract:Ultraflexible optical devices have been used extensively in next-generation wearable electronics owing to their excellent conformability to human skins. Long-term health monitoring also requires the integration of ultraflexible optical devices with an energy-harvesting power source; to make devices self-powered. However, system-level integration of ultraflexible optical sensors with power sources is challenging because of insufficient air operational stability of ultraflexible Polymer Light-Emitting Diodes. Here we develop an ultraflexible self-powered organic optical system for photoplethysmogram monitoring by combining air-operation-stable Polymer Light-Emitting Diodes, organic solar cells, and organic photodetectors. Adopting an inverted structure and a doped polyethylenimine ethoxylated layer, ultraflexible Polymer Light-Emitting Diodes retain 70% of the initial luminance even after 11.3 h of operation under air. Also, integrated optical sensors exhibit a high linearity with the light intensity exponent of 0.98 by Polymer Light-Emitting Diode. Such self-powered, ultraflexible photoplethysmogram sensors perform monitoring of blood pulse signals as 77 beats per minute. Flexible electronic devices remain an attractive technology for optical sensor applications that require long-term health monitoring and conformability on human skin. Here, the authors report an ultrathin self-powered integrated organic optical system for plethysmogram monitoring.
Showan Chen - One of the best experts on this subject based on the ideXlab platform.
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acridan grafted poly biphenyl germanium with high triplet energy low polarizability and an external heavy atom effect for highly efficient sky blue tadf electroluminescence
Angewandte Chemie, 2019Co-Authors: Miaoken Hung, Kuenwei Tsai, Sunil Sharma, Showan ChenAbstract:We propose the novel σ-π conjugated Polymer poly(biphenyl germanium) grafted with two electron-donating acridan moieties on the Ge atom for use as the host material in a Polymer Light-Emitting Diode (PLED) with the sky-blue-emitting thermally activated delayed fluorescence (TADF) material DMAC-TRZ as the guest. Its high triplet energy (ET ) of 2.86 eV is significantly higher than those of conventional π-π conjugated Polymers (ET =2.65 eV as the limit) and this guest emitter (ET =2.77 eV). The TADF emitter emits bluer emission than in other host materials owing to the low orientation polarizability of the germanium-based Polymer host. The Ge atom also provides an external heavy-atom effect, which increases the rate of reverse intersystem crossing in this TADF guest, so that more triplet excitons are harvested for light emission. The sky-blue TADF electroluminescence with this host/guest pair gave a record-high external quantum efficiency of 24.1 % at maximum and 22.8 % at 500 cd m-2 .
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Electric-Field-Induced Excimer Formation at the Interface of Deep-Blue Emission Poly(9,9-dioctyl-2,7-fluorene) with Polyelectrolyte or Its Precursor as Electron-Injection Layer in Polymer Light-Emitting Diode and Its Prevention for Stable Emission and Higher Performance
2018Co-Authors: Kuenwei Tsai, Tzu-hao Jen, Showan ChenAbstract:Conjugated polyelectrolytes and their precursors as electron-injection layer (EIL) in Polymer Light-Emitting Diode have attracted extensive attention because they allow the use of environmentally stable high work function metals as cathode with efficient electron injection. Here, for the first time, we find that an undesirable green emission component (470–650 nm) in the electroluminescence spectra is observed during continuous operation of deep-blue emission β-phase poly(9,9-dioctyl-2,7-fluorene) (β-PFO) device upon introducing polyelectrolyte poly[9,9-bis(6′-(18-crown-6)methoxy)hexyl fluorene] chelating to potassium ion (PFCn6:K+) as EIL. This phenomenon also happens to nonchelating PFCn6, poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)], or even nonemissive poly[4-((18-crown-6)methoxy)methyl styrene] chelating to K+ (PSCn6:K+). It can be ascribed to electric-field induction accompanied by thermal motion of a highly polar side chain in the polyelectrolyte leading to local segmental alignment of PFO main chains at the emitting layer (EML)/EIL interface and thus formation of green emission excimer, which is supported by the following observations: appearance of green emission component using nonemissive PSCn6:K+ as EIL, absence of green emission component as the device is operated at low-temperature (78 K) at which molecular thermal motion are frozen, and absence of green emission upon introducing 2,2′,2″-(1,3,5-phenylbenzenetriyl)tris[1-phenyl-1H-benzimidazole] as buffer layer in between EML and EIL for the prevention of direct contact of EML with polyelectrolyte or its precursor EIL
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polyethyleneoxide sodium dodecyl sulfate as hole blocking electron transporting layer for high performance blue Polymer light emitting Diode with oxygen and moisture stable aluminum cathode
Applied Physics Letters, 2010Co-Authors: Weichun Hung, Guanhong Lin, Showan ChenAbstract:We present the case of the blend of polyethyleneoxide (PEO) with sodium dodecyl sulfate (SDS) as a hole-blocking (HB)/electron-transporting (ET) layer to allow the use of oxygen- and moisture-stable aluminum (Al) as the cathode for achieving high-performance Polymer Light-Emitting Diode. With inserting the PEO-SDS layer (at the weight ratio 1:1.25), the blue-emitting device with poly(9,9-di-n-octylfluorene) exhibits the maximum brightness 12 300 cd/m2 and current efficiency 2.8 cd/A, much higher than the device without this layer (0.3 cd/m2 and 0.005 cd/A) and that using CsF/Al as the cathode (5835 cd/m2 and 1.06 cd/A). This HB-ET layer can also improve the performances of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene]-based device with Al as the cathode.
Richard H Friend - One of the best experts on this subject based on the ideXlab platform.
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charge trap assisted high efficiency in new Polymer blend based light emitting Diodes
Nano Energy, 2016Co-Authors: Kamran Ul Hasan, Juifen Chang, Haider Butt, Muhammad Hassan, Richard H FriendAbstract:Abstract Polymer blend system, F81−xSYx, based on mixture of poly (9,9-dioctylfluorene) (F8) and a poly (para-phenylenevinylene) (PPV) coPolymer, superyellow (SY), has been proven to be a high performance blend material in Polymer light emitting Diode (PLED). This blend system exhibits luminance (L) >104 cd m−2, luminous efficiency (η) >21 cd A−1 and low operating voltage (V) ~3–10 V. The performance can be credited to the large difference (~0.6 eV) between the highest occupied molecular orbital (HOMO) levels of F8 (~5.8 eV) and SY (~5.2 eV), where, SY molecules serve as hole-traps in the F8 host Polymer and reduce their mobility. This dictates a balanced charge injection into the emissive layer and results in overall increase in the device performance.
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electrical degradation of triarylamine based light emitting Polymer Diodes monitored by micro raman spectroscopy
Chemical Physics Letters, 2004Co-Authors: Jiseon Kim, Craig E Murphy, Alex Seeley, Ilaria Grizzi, J H Burroughes, Richard H FriendAbstract:Although much progress has been made in improving Polymer Light-Emitting Diode performance, there has been little work to address device intrinsic degradation mechanisms due to the challenge of tracking minute chemical reactions in the 100-nm-thick buried active layers during operation. Here we have elucidated a hole-mediated electrical degradation of triarylamine-based blue Polymer Diodes using in situ Raman microspectroscopy. A slow irreversible hole-doping of Polymer adjacent to the hole-injecting conducting-Polymer leads to formation of oxidised triarylamine species counterbalanced by anions from the conducting-Polymer. These charged species act as luminescence quenchers and hinder further hole injection across the interface leading to significant decreases in current density at low voltages.
Ulrich S Schubert - One of the best experts on this subject based on the ideXlab platform.
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inkjet printing of zinc ii bis 2 2 6 2 terpyridine metalloPolymers printability and film forming studies by a combinatorial thin film library approach
Macromolecular Rapid Communications, 2012Co-Authors: Christian Friebe, Andreas Wild, Jolke Perelaer, Ulrich S SchubertAbstract:For the first time, thin-film libraries of zinc(II) bis-2,2′:6′,2″-terpyridine metalloPolymers are prepared by inkjet printing to study structure–property relationships and their possible usage for organic photovoltaic (OPV) or Polymer Light-Emitting Diode (PLED) applications. By using a combinatorial approach, various important parameters, including solvent system, dot spacing, and substrate temperature, as well as UV-vis absorption and emission properties, are screened in a materials efficient and reproducible manner. Homogeneous films with a thickness of 150 –200 nm were obtained when printed at 40 –50 °C and from a solvent mixture of N,N-dimethylformamide and acetophenone in a ratio of 90/10. In applications such as OPV and PLEDs the control over film thickness and homogeneity are central to obtain good device properties.
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inkjet printing of Polymers state of the art and future developments
Advanced Materials, 2004Co-Authors: De Bj Berendjan Gans, P C Duineveld, Ulrich S SchubertAbstract:Inkjet printing is considered to be a key technology in the field of defined Polymer deposition. This article provides an introduction to inkjet printing technology and a short overview of the available instrumentation. Examples of Polymer inkjet printing are given, including the manufacturing of multicolor Polymer Light-Emitting Diode displays, Polymer electronics, three-dimensional printing, and oral dosage forms for controlled drug release. Special emphasis is placed upon the utilized Polymers and conditions, such as Polymer structure, molar mass, solvents, and concentration. Studies on viscoelastic fluid jets and the formation of viscoelastic droplets under gravity indicate that strain hardening is the key parameter that determines the inkjet printability of Polymer solutions.