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We have developed a metal-free process for the aerobic photooxygenation of sulfides to sulfoxides mediated by riboflavin tetraacetate or riboflavin (vitamin B2) photocatalysts and visible light (450 nm) in an acetonitrile-water (85:15 v/v) mixture. The optimised solvent system leads to both singlet-oxygen and electron-transfer pathways in photooxygenation, thus allowing oxidation of electron-poor and electron-rich thioanisoles, dialkyl sulfides and sterically hindered sulfides. Besides having a broad substrate scope, the method has very short reaction times and requires low catalyst loading (down to 0.1 mol%). These properties are due to the high photocatalyst stability and the extremely high quantum yields (1.3 for thioanisole oxygenation). Moreover, the method is chemoselective, producing only sulfoxides without overoxidation to sulfones. Taking into account the broad substrate scope, high selectivity and high efficiency, this method distinguishes itself from those previously reported. Other advantages include easy work-up of the reaction mixture, the availability and biodegradability of the photocatalysts and mild reaction conditions. We demonstrated, on a preparative scale, its practical application in the synthesis of the psychostimulant modafinil, in the selective oxidation of methionine derivatives, and in the detoxification of mustard gas. [ABSTRACT FROM AUTHOR]

ABSTRACT Carrier balance is essential to obtain efficient emission in polymer light-emitting diodes (PLEDs). A new polymer 3P5O composed of alternating p-terphenyl and tetraethylene glycol ether segments is designed and synthesized by the Suzuki coupling reaction and successfully employed as hole-buffer layer to improve carrier balance. Multilayer PLEDs [ITO/PEDOT:PSS/ 3P5O/SY/LiF/Al], with Super Yellow (SY) as the emitting layer and 3P5O as the hole-buffer layer, reveal maximum luminance (17,050 cd/m2) and maximum current efficiency (6.6 cd/A) superior to that without the hole-buffer layer (10,017 cd/m2, 3.0 cd/A). Moreover, it also shows better performance than that using conventional BCP as hole-blocking layer [ITO/PEDOT:PSS/SY/BCP/LiF/Al (80 nm): 13,639 cd/m2, 4.1 cd/A]. The performance enhancement has been attributed to hole-buffering characteristics of 3P5O that results in improved carrier recombination ratio and wider carrier recombination region. Current results indicate that the 3P5O is a promising hole-buffer polymer to enhance the performance of optoelectronic devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 785-794 [ABSTRACT FROM AUTHOR]

ABSTRACT Two pyrene-functionalized oligofluorenes (TPA-PyF3 and CBP-PyF3) are prepared using the condensation reaction by the Friedel-Crafts procedure. In the produced oligomers, the triphenylamine or N, N′-dicarbazolyl-4,4′-biphenyl core serves as a spacer bearing spiro-linked fluorene moieties to form a multi-H shaped structure. This specific structure efficiently retards the crystallization tendency of the pyrene groups, and gives the materials completely amorphous morphological structure and film forming ability. Solution-processed OLEDs with the structure of ITO/PEDOT:PSS (25 nm)/TPA-PyF3 or CBP-PyF3 (40 nm)/TPBI (35 nm)/Ca (10 nm)/Ag (100 nm) show low turn-on voltages of 3.6 V, and the maximum external quantum efficiencies reach 1.78% and 2.07% for TPA-PyF3 and CBP-PyF3, respectively. Moreover, both devices exhibit stable deep-blue light emission with Commission International de I'Eclairage (CIE) coordinates of around (0.16, 0.09) at the brightness of 100-1000 cd m−2. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 795-801 [ABSTRACT FROM AUTHOR]

Time-resolved photoluminescence (TRPL) of the blue and green LEDs, which has the same number of quantum-well (QW) pairs and the different etched depths, has been studied at room temperature. The purpose is to analyze the effect of different indium (In) content and defects density on TRPL. The carrier lifetime of radiative recombination and non-radiative for blue LED (In = 0.15) is 625.0 ns and 55.6 ns, and for green ones (In = 0.21), the figure is 363.6 ns and 35.0 ns. The carrier lifetime is reduced along with the increasing of In-component. As the etched depth deepened of blue LED, the non-radiative recombination lifetime tends to infinity. When it comes to low indium content, the PL spectra present a blue shift. With the increasing of indium mole fraction, the blue shift appeared at first, and then a red shift has been observed. And the spectral shift has disappeared, while etching the LEDs. At last, we clarify the results, through the band bending caused by polarization electric field. [ABSTRACT FROM AUTHOR]

This paper proposes a nonlinear approach of controlling the luminous intensity and correlated color temperature (CCT) of white light-emitting diode (LED) systems with dual color temperatures. This LED system is made up of a warm color LED source (2700 K) and a cool color LED source (5000 K). The luminous intensity of each of these LED sources is individually controlled by pulsewidth modulation. The overall intensity of the LED system is due to the combined emitted flux of both LED sources. Its overall CCT is the mixed average CCT of both LED sources. This proposed method is based on the nonlinear empirical luminous and CCT models of the LEDs, which take into consideration the thermal effect of LEDs on its luminance and CCT properties. With reasonable approximation, the theoretical models are simplified into practical solutions, which are translatable into real-life applications. It is experimentally validated that the proposed approach is considerably more accurate than the existing linear approaches that do not consider color variations of LED sources. The idea is applicable to LED systems with multiple color temperatures and is not limited to white LEDs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two series of oxime esters (OXE) based on different chromophores were synthesized as Type I photoinitiators. • Pyrene and Anthracene OXEs were selected as benchmark structures reacting mainly from S 1 or T 1. • Role of the excited state responsible of the cleavage of OXEs is discussed. • Pyrene-OXEs are the most efficient systems compared to Anthracene-OXEs. • A global excited state mechanism is provided. In this work, two series of oxime esters (OXE) based on Pyrene and Anthracene chromophores were synthesized and tested as Type Ⅰ photoinitiators for the Free Radical Photopolymerization (FRP) under visible irradiation at 405 nm using light-emitting diodes (LED) as the irradiation source. Interestingly, the two series of oxime esters only differ by the nature of the substituents connected to the oxime ester functional group. As a result of this modification, the reactivity of the different compounds only depends on the rate of decomposition from their excited states as well as the reactivity of the generated radicals. Remarkably, the 18 Pyrene-based OXEs (Py-OXE) and 17 Anthracene-based OXEs (An-OXE) were never synthesized prior to this work. Pyrene and Anthracene chromophores were selected as benchmark structures reacting mainly from their first excited singlet (S 1) and triplet (T 1) states, respectively. This will allow to shed some light on the excited states responsible of the cleavage of OXEs. Therefore, originality of this study relies in the difference of the initiation ability between these two families. In fact, the results showed that Py-OXEs (0.5 % w) are the most efficient systems compared to An-OXEs, so that higher final conversions and rates of polymerization could be obtained with Py-OXEs. Influence of the OXE structure (both chromophores and leaving groups) is discussed on the basis of different characterization techniques such as: UV–visible absorption spectroscopy, photolysis experiments, real-time Fourier transform infrared spectroscopy (RT-FTIR), stationary fluorescence and time-resolved fluorescence. Therefore, a global mechanism is finally provided based on the complementary characterization data. Oxime ester derivatives were also tested under air for the generation of 3D patterns (by Direct Laser Write DLW) using a diode laser at 405 nm. [ABSTRACT FROM AUTHOR]

ABSTRACT N, N'-dibutylquinacridone (DBQA) is utilized here for the first time as a high-performance panchromatic photoinitiator for the cationic polymerization (CP) of epoxides, the free radical polymerization (FRP) of acrylates, the thiol-ene polymerization and the synthesis of interpenetrated polymer networks (epoxide/acrylate) under violet, blue, green and yellow lights (emitted from LED at 405 nm, 470 nm, 520 nm, or 594 nm, or laser diode at 532 nm). It confers a panchromatic character to the photopolymerizable matrices. Remarkably, the proposed DBQA based photoinitiating systems exhibit quite excellent efficiency (the final monomer conversion for multifunctional monomers at room temperature can reach 62% and 50% in CP and FRP, respectively) and appear as much more powerful than the camphorquinone or Eosin-Y containing reference systems for visible light. For green light, DBQA is much more reactive than the literature reference (Eosin-Y) and for blue light, a good reactivity is found compared with camphorquinone. The photochemical mechanisms are studied by molecular orbital calculations, steady state photolysis, fluorescence, cyclic voltammetry, laser flash photolysis, and electron spin resonance spin trapping techniques. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1719-1727 [ABSTRACT FROM AUTHOR]

ABSTRACT A series of blue light-emitting hyperbranched polymers comprising poly(fluorene -co-dibenzothiophene- S, S-dioxide) as the branch and benzene, triphenylamine, or triphenyltriazine as the core were synthesized by an 'A2 + A2' + B3' approach of Suzuki polymerization, respectively. All resulted copolymers exhibited quite comparable thermal properties with the glass transition temperatures in the range of 59-68 °C and relatively high decomposition temperatures over 420 °C. Photoluminescent spectra exhibited slight variation with the molar ratio of the dibenzothiophene- S, S-dioxide unit and the size of the core units. Polymer light-emitting devices demonstrated blue emission with excellent stability of electroluminescence. Copolymers based on smaller core units of benzene and triphenylamine exhibited enhanced device performances regarding to that of triphenyltriazine. With the device configuration of ITO/PEDOT:PSS/polymer/CsF/Al, a maximum luminous efficiency of 4.5 cd A−1 was obtained with Commission Internationale de L'.Eclairage (CIE) coordinates of (0.16, 0.19) for the copolymer PFSO15B. These results indicated that hyperbranched structure can be a promising strategy to attain spectrally stable blue-light-emitting polymers with high efficiency. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1043-1051 [ABSTRACT FROM AUTHOR]

Light-emitting diodes (LEDs) have been widely used in liquid crystal display (LCD) backlight modules. In general, the light emitted by the LED backlight modules is not un-polarized light. However, our experiment results and analysis show that the light is partial polarization. The characteristics of partial polarization obtained in the experiment and analysis are utilized to increase the brightness of LCD backlight module, and then the results of this study demonstrate that the brightness can be increased by 46%. Thus, this study provides a method to increase the brightness of LCD backlight modules. [ABSTRACT FROM PUBLISHER]

ABSTRACT Naphthalimide-phthalimide derivatives (NDPDs) have been synthesized and combined with an iodonium salt, N-vinylcarbazole, amine or 2,4,6-tris(trichloromethyl)-1,3,5-triazine to produce reactive species (i.e., radicals and cations). These generated reactive species are capable of initiating the cationic polymerization of epoxides and/or the radical polymerization of acrylates upon exposure to very soft polychromatic visible lights or blue lights. Compared with the well-known camphorquinone based systems used as references, the novel NDPD based combinations employed here demonstrate clearly higher efficiencies for the cationic polymerization of epoxides under air as well as the radical polymerization of acrylates. Remarkably, one of the NDPDs (i.e., NDPD2) based systems is characterized by an outstanding reactivity. The structure/reactivity/efficiency relationships of the investigated NDPDs were studied by fluorescence, cyclic voltammetry, laser flash photolysis, electron spin resonance spin trapping, and steady state photolysis techniques. The key parameters for their reactivity are provided. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 665-674 [ABSTRACT FROM AUTHOR]

With the emergence of new color-mixing LED systems based on LED devices of different color temperatures, the need for a new modeling technique for LED systems with nonidentical LED devices becomes imminent. This paper presents a modeling technique for LED systems with LED arrays comprising nonidentical LED devices that have nonidentical optical-thermal-electrical properties. Based on a general 3-D photo-electro-thermal LED node model, LED devices of different kinds can be arranged in various array forms according to their system construction and design. By linking the system matrix to the correlated-color-temperature prediction, the proposed modeling technique provides an accurate prediction of the temperature distribution, luminous flux, and correlated color temperature of the LED systems. The temperature distribution and light output of the LED systems have been measured using an infrared imaging system and a spectrophoto-colorimeter with an integrating sphere. The modeling technique has been successfully demonstrated and experimentally verified on several LED systems comprising nonidentical LED devices. It is particularly useful as a modeling tool to study new color-mixing LED systems based on different types of LED devices. [ABSTRACT FROM AUTHOR]

ABSTRACT Two new thermally crosslinkable hole-transporting polymers, X-PTPA and X-PCz, were synthesized via Yamamoto coupling reactions. The number-averaged molecular weights ( Mn) of X-PTPA and X-PCz were found to be 45,000 and 48,000, respectively, and therewith, polydispersity indices were of 1.8 and 1.7, respectively. Thermally crosslinked X-PTPA and X-PCz exhibit excellent solvent resistance and stable optoelectronic properties. The UV-visible maximum absorption peaks of X-PTPA and X-PCz in the thin film state are at 389 and 322 nm, respectively. The HOMO levels of X-PTPA and X-PCz are estimated to be −5.27 and −5.39 eV, respectively. Multilayered devices (ITO/crosslinked X-PTPA or X-PCz/SY-PPV/LiF/Al) were fabricated with SY (SuperYellow) as the emitting layer. The maximum efficiency of the multilayered device with a crosslinked X-PTPA layer is approximately three times higher than that of the device without a crosslinked X-PTPA layer and much higher than that of the crosslinked X-PCz device. This result can be explained by the observations that crosslinked X-PTPA produces increased electron accumulation within the emitter, SY, and also efficient exciton formation due to improved charge balance. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 5111-5117 [ABSTRACT FROM AUTHOR]

The advantages of blue InGaN light-emitting diodes (LED) with the active region of gradually increased barrier heights from n- to p-layers are studied. The energy band diagram, hole concentration, electrostatic field near the electron blocking layer (EBL), and the internal quantum efficiency (IQE) are investigated by Crosslight simulation program. The simulation results show that the structure with gradually increased barrier heights has better performance over the equal one, which can be attributed to the mitigated polarization effect near the interface of the last barrier/EBL due to less interface polarization charges. Moreover, reduced barrier height toward the n-layers is beneficial for holes injection and transportation in the active region. As a result, holes are injected into the active region more efficiently and distributed uniformly in the quantum wells, with which both the IQE and the total lighting power are increased. Although it can lead to the broadening of the spontaneous emission spectrum, the increase is slight such that it has little effect on the application in solid-state lighting. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, several benazoxoazol derivatives have been rapidly and effectively synthesized by microwave irradiation and their physical properties (i.e. specific gravities, thermal resistance, and florescent performances) have also been investigated. Since lab-made organic phosphors (OP-1 and OP-2) exhibit high fluorescent efficiencies, low specific gravities, and excellent thermal resistance, we have applied them for the encapsulation of white light-emitting diodes (LEDs) as phosphors. Experimental results reveal that OP-1 and OP-2 possess appropriate emitting wavelengths and their electroluminescent properties highly depend upon their chemical structures, thus causing the diverse hues of white LEDs with them. The hues of white LEDs with OP-1 and OP-2 are CIE x,y =(0.35, 0.34) and CIE x,y =(0.25, 0.24), respectively. [Copyright &y& Elsevier]

In order to solve the low light inefficient of GaN-based LEDs, the parameters of the double grating structure light-emitting diodes are designed. The FDTD method was used to simulate the light field energy flow density and the light efficiency of LED, and the dynamic effects between grating height, grating period and duty cycle were calculated. And the characteristic parameters and light efficiency of the light-emitting diodes are analyzed to maximize the light extraction efficiency. [ABSTRACT FROM AUTHOR]

This paper proposes a thermal parameter extraction method for light-emitting diode (LED) devices and LED systems (LEDs mounted on a heatsink). The proposed method provides a simple tool to find out the essential thermal parameters involved in the LED systems, including thermal resistance of LEDs, thermal capacitance of LEDs and thermal time constant of LEDs. All of these thermal parameters are essential for both reliability research and optimal design of LEDs. The concept and significance of the Tau (thermal time constant) of LEDs are emphasized in this paper. Heat transfer equations are initially used for LED devices and LED systems to predict the rising-up junction temperature and cooling-down junction temperature of the LED device and the LED system. Experiments on several LEDs and heatsinks at different time frames are conducted and the practical measurements confirmed the validity of this method and accuracy of the predicted thermal parameters of LEDs. [ABSTRACT FROM AUTHOR]

Polyfluorene PF•γCD rotaxane copolymer, composed of randomly distributed 9,9-dioctylfluorene, methyltriphenylamine (electron-donating) and 9-dicyanomethylenefluorene complexed with γ-cyclodextrin (γCD) (electron-accepting) structural units, has been synthesized by Suzuki cross-coupling reaction. The chemical structures were proved by FTIR and 1H NMR spectroscopy. The surface morphology, thermal, optical, electrochemical behavior, and adhesion characteristics of the obtained rotaxane copolymer have been investigated and compared with those of the nonrotaxane counterpart ( PF). Relatively high fluorescence efficiency, almost identical normalized absorbance maximum in solution and solid-state of PF•γCD rotaxane copolymer, and a more uniform and smoother surface with lower adhesion forces provides the role of γCD encapsulation on the lower aggregation propensity. PF•γCD and PF copolymers exhibit n- and p-doping processes and blue-light emission in the film state. The optical and electrochemical band gaps (Δ Eg), as well as the highest occupied molecular orbital/lowest unoccupied molecular orbital positions in an energetic diagram indicate that both copolymers are promising blue-emitting electroluminescent materials. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

We describe a facile fabrication of white light-emitting cadmium sulfide (CdS)-poly(HEA- co-NVK) nanocomposites [2-hydroxyethyl acrylate (HEA) and N-vinylcarbazole (NVK)] via plasma-ignited frontal polymerization (PIFP), a novel and rapid reaction mode of converting monomers into polymers in minutes. Frontal polymerization was initiated by igniting the upper side of the reactant with plasma. Once initiated, no additional energy was required for the polymerization to occur. The chemical functional groups of the as-prepared nanocomposites were thoroughly investigated using Fourier transform infrared spectra. The dependence of the front velocity and front temperature on the initiator concentration and weight ratios of HEA/NVK was also investigated in detail. Perhaps more interestingly, the white light-emitting materials synthesized by ingeniously incorporating the compensating colors of yellow emitting from 3-(trimethoxysilyl)-1-propanethiol-capped CdS nanocrystals and blue emitting from carbazole-containing polymer were conveniently applied onto a commercial UV light-emitting diode (LED) to generate white LEDs. The subtle change in the weight ratios of CdS/NVK can significantly impact the color hue. The white light becomes gradually colder with the increase of NVK, but becomes gradually warmer with the increase concentration of CdS nanocrystals. In a broad perspective, these white light-emitting materials designed by PIFP approach will open a new pathway to develop 'QD-polymer nanocomposite down-conversion LED' in a fast and efficient way. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

This study reports the synthesis, curing, and optoelectronic properties of a solution-processable, thermally cross-linkable electron- and hole-blocking material containing fluorene-core and three periphery N-phenyl- N-(4-vinylphenyl)benzeneamine ( FTV). The FTV exhibited good thermal stability with Td above 478 °C in nitrogen atmosphere. The FTV is readily cross-linked via terminal vinyl groups by heating at 160 °C for 30 min to obtain homogeneous film with excellent solvent resistance. Multilayer PLED device [ITO/PEDOT:PSS/cured- FTV/MEH-PPV/Ca (50 nm)/Al (100 nm)] was successfully fabricated using solution processed. Inserting cured- FTV is between PEDOT:PSS and MEH-PPV results in simultaneous reduction in hole injection from PEDOT:PSS to MEH-PPV and blocking in electron transport from MEH-PPV to anode. The maximum luminance and maximum current efficiency were enhanced from 1810 and 0.27 to 4640 cd/m2 and 1.08 cd/A, respectively, after inserting cured- FTV layer. Current results demonstrate that the thermally cross-linkable FTV enhances not only device efficiency but also film homogeneity after thermal curing. FTV is a promising electron- and hole-blocking material applicable for the fabrication of multilayer PLEDs based on PPV derivatives. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 000: 000-000, 2012 [ABSTRACT FROM AUTHOR]

A monomer containing bent side chains with oxadiazole unit was synthesized. And it was copolymerized with polyfluorene at different ratios. The photophysical and electrochemical properties of the copolymers were characterized. The results show that the introduction of the oxidiazole-containing side chains into the polymer reduces the lowest unoccupied molecular orbital level. And the steric hindrance of the side groups can effectively suppress the aggregation of the polymer backbones. Electroluminescent devices were fabricated with a configuration of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene (PEDOT):PSS/Sample/Ca/Al. All of the devices emit blue light. The device of the copolymer PFOXD50 shows the best performance with the maximum luminance of 1033 cd/m2 and the maximum current efficiency of 0.29 cd/A. Then a cyclometalated iridium complex monomer (ppy)2Ir(BrPhPyBr) was copolymerized with PFOXD50 at different ratios. The devices with the same configuration emit orange light. The efficiency generally increases with the increasing Ir content. Among them, the device of the copolymer PFOXDIr7 shows the best performance with the maximum luminance of 846 cd/m2 and the maximum current efficiency of 0.61 cd/A. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

We report novel host polymers for a high-efficiency polymer-based solution-processed phosphorescent organic light-emitting diode with typical blue-emitting dopant bis(4,6-difluorophenylpyridinato-N,C2)iridium(III) picolinate (FIrpic). The host polymers, soluble polynorbornenes with pendant carbazole derivatives, N-phenyl-9 H-carbazole ( P1), N-biphenyl-9 H-carbazole ( P2), and 9,9′-(1,3-phenylene)bis-9 H-carbazole (mCP) ( P3) are efficiently synthesized by vinyl addition polymerization of norbornene monomers using Pd(II) catalyst in combination with 1-octene chain transfer agent. The polymers exhibit high thermal stability with high decomposition ( Td5 > 410 °C) and glass transition temperatures ( Tg ≈ 268 °C). The HOMO ( ca. −5.5 to −5.7 eV) and LUMO ( ca. −2.0 to −2.1 eV) levels with the high triplet energy of about 2.7-3.0 eV suggest that the polymers are suitable for a host material for blue emitters. Among the solution-processed devices that were fabricated based on the emissive layers containing the P1− P3 host doped with various concentrations of FIrpic (7-13 wt %), the best device with P3 host exhibits power efficiency of 3.0 lm W−1 and external quantum efficiency of 4.0% at a luminance of 1000 cd m−2 that is outstanding among the polymeric rivals. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Blue light-emitting materials are receiving considerable academic and industrial interest due to their potential applications in optoelectronic devices. In this study, blue light-emitting copolymers based on 9,9′ -dioctylfluorene and 2,2′-(1,4-phenylene)-bis(benzimidazole) moieties were synthesized through palladium-catalyzed Suzuki coupling reaction. While the copolymer consisting of unsubstituted benzimidazoles (PFBI0) is insoluble in common organic solvents, its counterpart with N-octyl substituted benzimidazoles (PFBI8) enjoys good solubility in toluene, tetrahydrofuran, dichloromethane (DCM), and chloroform. The PFBI8 copolymer shows good thermal stability, whose glass transition temperature and onset decomposition temperature are 103 and 428 °C, respectively. Its solutions emit blue light efficiently, with the quantum yield up to 99% in chloroform. The electroluminescence (EL) device of PFBI8 with the configuration of indium-tin oxide/poly(ethylenedioxythiophene):poly(styrene sulfonic acid)/PFBI8/1,3,5-tris(1-phenyl-1H-benzimidazole-2-yl)benzene/LiF/Al emits blue light with the maximum at 448 nm. Such unoptimized polymer light-emitting diode (PLED) exhibits a maximum luminance of 1534 cd/m2 with the current efficiency and power efficiency of 0.67 cd/A and 0.20 lm/W, respectively. The efficient blue emission and good EL performance make PFBI8 promising for optoelectronic applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

To study influence of the donor(D)-acceptor(A) units and pendent mode of phosphorescent moiety on the opto-electronic properties for its resulting copolymers, two D-A-based polyfluorene derivatives ( P1 and P2) pending the red-emitting iridium bi(phenylisoquilonato) (picolinato) [Ir(Piq)2(pic)] unit and a polyfluorene derivative ( P3) only pending Ir(Piq)2(pic) unit were synthesized and characterized, in which the donor of carbazole, the acceptor of oxadiazole are grafted into the C-9 position of fluorene, the Ir(Piq)2(pic) unit is pended into either the C-9 position for P1 and P3 or the end for P2 of fluorene by unconjugated linkage, respectively. Their opto-electronic properties were significantly influenced by the D-A units and pendent mode of the Ir(Piq)2(pic) unit. In the polymer light-emitting devices with a configuration of ITO/PEDOT/polymers/LiF/Al, the P1 showed best electroluminescent properties than the P2 and P3. The maximum current efficiency of 0.72 cd/A and the highest luminance of 1398 cd/m2 were obtained in the P1-based device, which are 1.3 and 1.5 times higher than those in the P2-based device, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

A series of conjugated (poly{N-(2-ethylhexyl)-3,6-carbazole-vinylene-alt-[(2,5-bisphenyl)-1,3,4-oxadiazole]}) and nonconjugated (poly{N-(2-ethylhexyl)-3,6-carbazole-vinylene-alt-[(2,5-bisphenol)-1,3,4-oxadiazole]}) and poly{9,9-dihexyl-2,7-fluorene-vinylene-alt-[(2,5-bisphenol)-1,3,4-oxadiazole]}) polymers containing oxadiazole and carbazole or fluorene moieties in the polymer backbone were synthesized with a multiple-step procedure. The properties of the polymers, including the photophysical and electrochemical characteristics, could be fine-tuned by adjustment of the components or structures in the polymer chains. The polymers were used to examine the hole-injection/transport behavior as hole-injection/hole-transport layers in double-layer indium tin oxide (ITO)/polymer/aluminum tris(8-hydroxyquinoline)/LiF/Al devices by the determination of their energy levels. The effects of the polymers in these devices on the charge-transport behavior were compared with a control device fabricated with poly(ethylenedioxythiophene) (PEDOT)-poly(styrene sulfonate) (PSS). Devices containing the synthesized polymers showed comparable adhesion to the ITO anode and good hole-injection/transport performance. In addition, they exhibited higher electroluminescence over an identical range of current densities than the control device. This was attributed to the prevention of radiative exciton quenching caused by the PEDOT-PSS interfaces and the improvement of electron/exciton blocking due to the higher electron affinity of the synthesized polymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

Abstract: Two novel diketopyrrolopyrrole (DPP)-based copolymers P1–2 were prepared by doping red emitting DPP monomer (1mol%) into benzothiadiazole, alkoxybenzene and 9,9-dialkylfluorene-based copolymers through base-free Suzuki polymerization. P1 contained the pendants of electron-transport oxadiazole and hole-transport carbazole, but P2 did not contain them. P1 had higher glass transition temperature than P2. The electroluminescence (EL) devices of P1 and P2 (ITO/PEDOT:PSS/polymer/CsF/Al) exhibited red emission with external quantum efficiency of 0.63% and 0.18%, and with brightness of 2681 and 885cd/m2, respectively. The results show that the EL properties of P1 are much better than that of P2 due to the introduction of oxadiazole and carbazole as the pendants. The pendants could restrain aggregation which might induce fluorescence quenching and are of benefit to keep high charge mobility. The efficient energy transfer existed among the pendants, polymer backbone and DPP unit. These factors should be responsible for the higher EL performance of P1. [Copyright &y& Elsevier]

Abstract: ZnO nanorod arrays were effectively selective-grown on a p-type GaN:Mg layer through chemical bath deposition (CBD) at a low temperature hydrothermal synthesis (85°C) with a ZnO seed layer. The 5μm-diameter hole-array patterns of the ZnO seed layer were grown on a p-type GaN:Mg layer in aqueous solution with a mercury lamp illumination. The diameter and the height of ZnO nanorods were measured as the values of 500nm and 3μm, respectively. The growth orientation, surface morphology, and aspect ratio of the ZnO nanorods can be controlled and formed on the hole-array patterned ZnO seed layer. The peak wavelength of the photoluminescence spectrum was measured at 384nm. [Copyright &y& Elsevier]

A series of new low band gap π‐conjugated polymers containing N‐alkyldithieno[3,2‐b:2′,3′‐d]pyrrole, benzo[c][1,2,5]thiadiazole, and alkylthiophenes are reported. The polymerization condition was standardized and the use of CuO to obtain high‐molecular‐weight polymer was also realized. The molecular weight of the polymers was found to be in the range of 45,000–53,000. All the polymers were found to be soluble in most of the common organic solvents, such as chloroform, dichloromethane, THF, and chlorobenzene with excellent film forming properties. The λmax of the polymers was found to be in the range of 687–663 nm with band gap in the range of 1.35–1.43 eV. The oxidation potential of the polymers from cyclic voltammetry was determined to be 0.5–0.75 V. The HOMO levels of the above synthesized polymers were found to be between 5.24 and 5.54 eV. All the polymers exhibited a PL emission in between 755 and 773 nm. The polymers were found to be thermally stable above 277 °C with only a 5% weight loss. From the thermal stability values, it is expected that the current set of polymers are stable enough for the application in electronic devices. To realize the potential use of the polymers, EL devices were fabricated and found to show red emission with comparatively low threshold voltage. A brightness of 54 cd m−2 for the device with polymer PC could be reached. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6514–6525, 2009 [ABSTRACT FROM AUTHOR]

A novel series of soluble hyperbranched interrupted π‐conjugated polymers (HICPs) based on complicated 9,9‐diarylfluorenes (CDAFs) branching core and end‐capped with high carrier‐mobility pyrene moieties were synthesized via the "A2 + A′2 + B3" type Suzuki coupling condensation. The new polymer architecture improves the spectrum stability than the corresponding linear and hyperbranched polymers in PLEDs. Besides, it overcomes the drawback of high driving voltage of common interrupted π‐conjugated polymers. CDAF1 exhibits excellent thermal and morphological stability with a decomposition temperature (Td) higher than 445 °C and a glass transition temperature (Tg) up to 128 °C. No obvious low‐energy green emission band at 520 nm was observed under extreme thermal annealing conditions in air at 200 °C for 12 h. The CDAF1 device shows stable blue emission with the peak at 422 and 447 nm. The Commission International d'Eclairage (CIE) 1931 coordinates is (0.18, 0.16) and the brightness reaches 1051 cd/m2 at 15.7 V. White PLED based on CDAF1/MEH‐PPV blends exhibits a low turn‐on voltage of 4.8 V with voltage‐independent CIE of (0.32, 0.32). Molecular simulations were used to investigate the conformation and interchain interaction. HICPs based on CDAFs tethered with high‐mobility moieties are promising stable blue and host materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6451–6462, 2009 [ABSTRACT FROM AUTHOR]

• Traditional NLS regression-based standards showed higher prediction inaccuracy. • Accelerated degradation test designed to collect lumen degradation data for LEDs. • A probabilistic estimation of model parameters with a Bayesian method is presented. • Applied on two case studies of LED packages and lamps to validate proposed method. • Proposed method showed an improved accuracy compared with TM-21 and TM-28 methods. The introduction of high-power white LEDs has revolutionized the lighting industry in the past few decades due to the multiple benefits in terms of high reliability, environmental friendliness and versatile applications. However, challenges have arisen in assessing the reliability and lifetime prediction because it is difficult to record the failure data in a short period of time. Currently, the nonlinear least squares (NLS) regression-based method is used in industry for projecting the lumen maintenance lifetime from degradation data. The model parameters estimated using the NLS regression approach are deterministic and introduce high prediction errors. In this paper, a Bayesian method is proposed to estimate the remaining useful lifetimes (RULs) of both high-power white LED packages and lamps. The accelerated degradation tests conducted for gathering lumen degradation data are used to validate the proposed method. The exponential decay model is used as the degradation model and the parameters are estimated based on Markov Chain Monte Carlo (MCMC) sampling and using the Metropolis-Hasting (MH) algorithm. The lifetime prediction results showed that the Bayesian method has better prediction accuracy compared to the NLS method. Thus, the proposed Bayesian method is shown to be a promising approach to address the lifetime prediction issue for high-power white LEDs with improved prediction accuracy. [ABSTRACT FROM AUTHOR]

Nonconjugated bipolar transport polymers have been developed as host materials for electroluminescent devices by incorporating both electron‐transporting and hole‐transporting functionalities into copolymers. The random copolymer PCt‐nvk3‐7 containing mesogen‐jacketed segment of P‐Ct have been synthesized and characterized. The effect of mesogen‐jacketed segment content of these bipolar copolymers on device performance has been investigated. The results of polymer light‐emitting diodes (PLEDs) show that the jacketed content of copolymers has a significant effect on device performance: lowering charge transport and facilitating the hole‐electron recombination leads to much higher current efficiency. Applying these high triplet random copolymers as host, the maximum current efficiency of 0.70 cd/A and the maximum brightness of 1872.8 cd/m2 was achieved for PCt‐nvk3‐7 with an orange‐emitting complex dopant. The results suggest that the bipolar copolymers PCt‐nvks can be good host polymers for electrophosphorescent devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7861–7867, 2008 [ABSTRACT FROM AUTHOR]

Pd/TPPMS in THF/water bi-phase mixture: Clean Suzuki coupling system to synthesis of high molecular weight polyfluorene derivative The polymer with a molecular weight as high as 230,000 and a molecular weight distribution of 1.28 was achieved due to the moderate solubility of TPPMS in both THF and water phase. In the case of TPPDS ligand, polymerization activity was still observed, but the polymer product had only moderately high molecular weight and much broader molecular weight distribution. Keywords: catalysts; copolymerization; light-emitting diodes (LED) EN catalysts copolymerization light-emitting diodes (LED) 7268 7272 5 03/03/21 20081101 NES 081101 Hydrosoluble ligand I m i -sulfonatophenyl-diphenylphosphine (TPPMS) was applied in Suzuki coupling reaction for synthesis of blue light-emitting polymer, poly[2,7-(9,9-dioctylfluorene)- I co i - I N i -(4-(3-methylpropyl)-diphenylaniline]. [Extracted from the article]

We synthesized two fluorene‐based copolymers poly[(2,5‐bis(4‐hexylthiophen‐2‐yl)thiazolo[5,4‐day]thiazole‐5,5′‐diyl)‐alt‐(9,9′‐dioctylfluorene‐2,7‐diyl)] (PF‐TTZT), and poly[(5,5′‐bis(4‐hexylthiophen‐2‐yl)‐2,2′‐bithiazole‐5,5′‐diyl)‐alt‐(9,9′‐dioctylfluorene‐2,7‐diyl)] (PF‐TBTT), which contain the electron‐withdrawing moieties, thiazolothiazole, and bithiazole, respectively. Through electrochemical studies, we found that these two polymers exhibit stable reversible oxidation and reduction behaviors. Moreover, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PF‐TBTT are lower than those of PF‐TTZT, and the bandgap of PF‐TBTT is smaller than that of PF‐TTZT. Thus the bithiazole moiety in PF‐TBTT is more electron‐withdrawing than the thiazolothiazole moiety in PF‐TTZT. Light‐emitting devices with indium tin oxide (ITO)/poly(3,4‐ethylene dioxythiophene):poly(styrenesulfonate)(PEDOT)/polymer/bis(2‐methyl‐8‐quinolinato)‐4‐phenylphenolate aluminum (BAlq)/LiF/Al configurations were fabricated. The performance of the PF‐TBTT device was found to be almost three times better than that of the PF‐TTZT device, which is because electron injection from the cathode to PF‐TBTT is much easier than for PF‐TTZT. We also investigated the planarity and frontier orbitals of the electron donor‐acceptor (D‐A) moieties with computational calculations using ab initio Hartree–Fock with the split‐valence 6‐31G* basis set. These calculations show that TBTT has a more nonplanar structure than TTZT and that the bithiazole moiety is more electron‐withdrawing than thiazolothiazole. These calculations are in good agreement with the experimental results. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7148–7161, 2008 [ABSTRACT FROM AUTHOR]

Hyperbranched polymer-cored star polyfluorenes with high molecular weights and narrow molecular weight distribution were prepared by palladium-catalyzed one-pot Suzuki polycondensation of multifunctional cores and an AB-type monomer. The optical, electrochemical and thermal properties of the hyperbranched polymer-cored star polymers were investigated. These polymers exhibited good thermal and color stability in solid state, and there was no significant blue-green emission after the polymers had been annealed in air for 2.5 h. Their three-dimensional hyperbranched structures could effectively reduce the aggregation of the peripheral rigid linear conjugated polyfluorene chains. [ABSTRACT FROM AUTHOR]

Abstract: Vinyl polymer PDSB containing pendant 1,4-distyrylbenzene derivatives was prepared from its precursor poly(4-vinylbenzyl chloride) (PVBC: M w =10,400, PDI=1.12), which had been synthesized by the controlled radical polymerization (RAFT). PDSB is readily soluble in common organic solvents and basically amorphous material with 5% weight-loss temperature higher than 390°C. The HOMO level of PDSB, estimated from cyclic voltammetric data, is −5.15eV, which is higher than −5.8eV of PVK and thus effective in reducing the hole injection barrier between the PEDOT:PSS and emitting layer. The blend films of fluorescent isolated blue emitter (PDSB) and phosphorescent green system [PVK/Ir(ppy)3] were prepared to tune color emission. The blend films [PVK:PDSB:Ir(ppy)3] show composition-dependent behavior in PL spectral properties and EL characteristics. The PL spectra of the blend films [PVK:PDSB:Ir(ppy)3] show a major emission at 515nm and a minor peak at 454nm, which are attributed to Ir(ppy)3 and PDSB, respectively. The C.I.E. 1931 coordinates of the blend LED devices shift from (0.29, 0.61) for PVK:PDSB=10:0 to (0.25, 0.35) for PVK:PDSB=0:10 with the increase of PDSB content. [Copyright &y& Elsevier]

Abstract: A new series of soluble 3,6-carbazole–fluorene–silole copolymers (PCz–F–S) with M w up to 52.1kDa were synthesized by Suzuki coupling reactions. Chemical structures and optoelectronic properties of the copolymers were characterized by elemental analysis, NMR, UV absorption, cyclic voltammetry, photoluminescence (PL), and electroluminescence (EL) spectra. The main absorption peaks of solutions and films of the copolymers are at 354nm and 347nm, respectively, showing the combined contribution from the 3,6-carbazole and fluorene blocks. The silole absorption is at wavelength range between 400nm and 500nm. Compared with the solution absorption, largely decreased relative absorption of the silole to the 3,6-carbazole and fluorene blocks can be found for the films of the copolymers. The copolymers possess HOMO levels of around −5.36eV, mainly from the contribution of 3,6-carbazole. Under excitation, the films of the copolymers show silole-dominated green emissions because of PL excitation energy transfer, with high absolute PL quantum yields up to 86%. EL devices with a configuration of ITO/PEDOT/PCz–F–S/Ba/Al only display a maximum external quantum efficiency of 0.48% whereas a device configuration of ITO/PEDOT/PCz–F–S/TPBI/Ba/Al with TPBI hole blocking layer greatly boosts the efficiency to 3.03% for a practical brightness of 236cd/m2. The improved EL efficiency suggests that more balanced charge injection and transport can be realized by inserting the TPBI hole blocking layer. [Copyright &y& Elsevier]

Abstract: Polymers containing bis(indolyl)maleimides (P2b) and aminophenylsuccinimides (P1 and P3) were prepared from norbornene derivatives through ring-opening metathesis polymerization process. The chromophores P1–P3 exhibit intensive blue or red fluorescence in solutions, which showed significant solvatochromic effect due to intramolecular charge transfers. Mixing the blue emitting polymer with the red one formed a heterogeneous blend, which displayed dual emissions with compatible intensity. The light-emitting diodes (LEDs) fabricated by a single layer of such polymer blend displayed a broad range of visual colors depending on the relative ratio of the two components. White light can be obtained by a mixture of P1 (or P3) and P2b in a wt ratio of 10/3–10/5. The dual emission character was ascribed to the low miscibility between the two types of polymers, whereas energy transfer from the blue domain to the red one was retarded. The morphology of the solid film was verified by polarized-light optical microscopy. The emitting nature was also compared with those of random copolymers and monomer mixtures. [Copyright &y& Elsevier]

In this paper, we discuss the emission of visible light, by a monolithically integrated silicon diode under reverse bias. The emission of light is achieved using a special defect-engineered buried layer. The light is emitted as punctiform sources by the defects located at the p-n junction of the reverse-biased diode. The influence of the defects on the electrical behavior is manifested as a current-dependent electroluminescence. [ABSTRACT FROM AUTHOR]

Abstract: We prepared and characterized three new copoly(aryl ether)s (P1–P3) consisting of alternate electron-transporting 2,7-bis(3-(trifluoromethyl)phenyl)-9,9-dihexylfluorene and hole-transporting fluorophores (P1: 3,6-distyryl-N-2-ethylhexylcarbazole; P2: 2,7-distyryl-9,9-dihexylfluorene; P3: 1,4-distyryl-2,5-dihexylbenzene) separated by ether spacers. The copolymers were soluble in common organic solvents such as chloroform, NMP, and 1,1,2,2-tetrachloroethane and exhibited good thermal stability with T ds higher than 360°C. Optical properties of P1–P3 were investigated by comparing their absorption and photoluminescence spectra with those of compositional model compounds M1–M4. The emissions of P1–P3 are originated from both fluorophores (P1) or dominated by fluorophores with longer emissive wavelength via efficient energy transfer (P2 and P3). Cyclic voltammetric investigations confirm that incorporation of isolated hole- and electron-transporting segments leads to simultaneous enhancement of electron and hole affinity in these copoly(aryl ether)s. The HOMO and LUMO energy levels of P1–P3 are −5.15, −5.28, −5.17 and −3.04, −3.06, −3.08eV, respectively, and double-layer light emitting diodes of P1–P3 reveal emission maxima around 450–500nm. [Copyright &y& Elsevier]

Abstract: New fluorene-based alternating copolymers (PFPhPhCN, PFPhThCN, and PFThThCN) containing different comonomers have been designed and subsequently synthesized via Pd-catalyzed Suzuki polymerization. The synthesized polymers could be well characterized by 1H NMR, FT-IR, and elemental analyses. These polymers were found to be thermally stable and readily soluble in common organic solvents. The UV–vis absorption maxima of PFPhPhCN, PFPhThCN, and PFThThCN were 399, 456 and 499nm, and the PL maxima were 484, 539 and 620nm, respectively. The emitting color of the homopolymer, poly(9,9-dioctylfluorene-2,7-diyl) (PDOF), could be tuned by incorporating various low band gap dyes into the polymer main-chain. The absorption and emission maxima of the copolymers were varied according to the type of incorporated aromatic group (thiophene or phenylene). In particular, PFThThCN exhibited almost pure red emission (chromaticity values x =0.63, y =0.37). [Copyright &y& Elsevier]

Abstract: This review covers recent developments in the molecular design and synthesis of metal-based functional materials of fluorenes and their derivatives. Conjugated organic compounds containing metal centers constitute an important class of molecular materials nowadays because of the combined good features of the chemical, electrochemical, electronic and optical properties of the metal groups to those of the organic chromophores. Recently, substituted fluorene derivatives have been extensively explored in the field of optoelectronics and molecular electronics. They are synthetically easily accessible and possess high thermal and chemical stability as well as high emission quantum yields. Such rapidly emerging chemistry of organic-based fluorene derivatives leads us to believe that a related chemistry involving metal centers should present a fascinating subclass and pose potential for the development of new types of novel materials. While there is great scope for chemical modifications of the metal units and structure of the fluorene ring and its substituents in a systematic fashion, these classes of metal–organics can exhibit rich photophysical, redox and structural properties. An understanding of the structure–property relationships of these molecules allows us to establish good model systems in the development of optoelectronic devices, molecular electronics and chemical sensing applications. In this article, homo- and heterometallic systems containing fluorene chromophores and their structural analogues such as carbazoles and diazafluorenes are discussed, and particular attention is paid to chemical reactivities, electronic absorption spectroscopy, photoluminescence and redox behavior, and structural aspects of these metal–organic compounds. The applications that these materials have found in various domains are also highlighted. [Copyright &y& Elsevier]

In the last couple of decades, high-performance electronic and optoelectronic devices based on semiconductor heterostructures have been required to obtain increasingly strict and well-defined performances, needing a detailed control, at the atomic level, of the structural composition of the buried interfaces. This goal has been achieved by an improvement of the epitaxial growth techniques and by the parallel use of increasingly sophisticated characterization techniques. Among them, a leading role has been certainly played by those exploiting synchrotron radiation (SR) sources. In fact synchrotron radiation has distinct advantages as a photon source, notably high brilliance and continuous energy spectrum; by using the latter characteristic atomic selectivity can be obtained and this is of fundamental help to investigate the structural environment of atoms present only in a few angstrom (Å) thick interface layers of heterostructures. The third generation synchrotron radiation sources have allowed to reach the limit of measuring a monolayer of material, corresponding to about 1014 atoms/cm2. Since, in the last decade, the use of intentionally strained heterostructures has greatly enhanced the performance of electrical and electro-optical semiconductor, a particular attention will be devoted to intentionally strained superlattices.First the effect of strain on the band lineups alignments in strained heterostructures will be discussed deeply. Then the attention will be focused on to review the most important results obtained by several groups in the characterization of semiconductor heterostructures using the following structural SR techniques: (i) X-ray absorption-based techniques such as EXAFS, polarization-dependent EXAFS, surface EXAFS and NEXAFS (or XANES); (ii) X-ray diffraction-based techniques such as high-resolution XRD, grazing incidence XRD, XRD reciprocal space maps, X-ray standing waves and diffraction anomalous fine structure (DAFS); (iii) photoelectron-based techniques. [Copyright &y& Elsevier]

A PPV-based conjugated copolymer DIOXA-PPV containing electron-affinitive bis-1,3,4-oxadiazole and hole-transporting distyrylbenzene derivative was synthesized via Horner–Wadsworth–Emmons reaction. The HOMO, LUMO energy levels and band gap of DIOXA-PPV are determined to be −5.06, −2.98 and 2.08 eV, respectively. The photoluminescence (PL) maxima show gradually transition from 515 to 544 nm as the concentrations of DIOXA-PPV in C2H2Cl4 increase from 10−7 to 10−3 M due to the formation of excimer. Single-layer light-emitting diode (LED) with a structure of ITO/DIOXA-PPV/Al emits bright yellow emission, the threshold voltage and maximum luminance are 4.6 V and 188 cd/m2, respectively. The EL emission maximum locates at 541 nm, which is corresponding to the excimer emission. [Copyright &y& Elsevier]

Purpose: Computer vision syndrome (CVS) is one of the most frequently encountered problems among video display terminals (VDT) users, but little is known regarding the short-term effect after exposure to light-emitting diodes (LED). The purpose of this study was to determine if short-term exposure to LED leads to changes in corrected distance visual acuity (CDVA), lipid layer thickness (LLT), blink rates, partial blink ratio, and computer vision syndrome questionnaire (CVS-Q) score., Design: Prospective, cross-sectional study., Methods: In this study, participants were recruited at the National Cheng-Kung University Hospital, a tertiary referral center in southern Taiwan, for examination. Participants were asked to complete the CVS-Q and undergo a series of ocular examinations, including CDVA, LLT, blink rates and partial blink ratio before and after watching an LED display for 15 min. Main Outcome Measures were changes in CDVA, LLT, blink rates, partial blink ratio, and CVS-Q measurements., Results: In total, 120 eyes from 60 participants (mean age: 35.7 ± 9.4 years) were included; 31 participants were men (51.7%), and 29 were women (48.3%). The CDVA, LLT, blink rates, and partial blink ratio did not change after watching the LED display. The CVS-Q score significantly improved after short-term LED exposure ( P < 0.001). A subgroup analysis of subjects with a baseline LLT of <60 nm or ≥60 nm determined that LLT significantly decreased in individuals with a baseline LLT of ≥60 nm ( P = 0.016)., Conclusion: Short-term use of LED displays reduced LLT in individuals with a baseline LLT of ≥60 nm, despite the visual symptoms of CVS improved subjectively. Therefore, digital device users should be aware of the potential negative effects of LED exposure on the eyes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Lin, Hung and Huang.)