Fluorescence/phosphorescence hybrid white organic light-emitting devices（WOLEDs） based on double emitting layers（EMLs） with high color stability are fabricated.The simplified EMLs consist of a non-doped blue therm...Fluorescence/phosphorescence hybrid white organic light-emitting devices（WOLEDs） based on double emitting layers（EMLs） with high color stability are fabricated.The simplified EMLs consist of a non-doped blue thermally activated delayed fluorescence（TADF） layer using 9,9-dimethyl-9,10-dihydroacridine-diphenylsulfone（DMAC-DPS） and an ultrathin non-doped yellow phosphorescence layer employing bis[2-（4-tertbutylphenyl）benzothiazolato-N,C2＇]iridium（acetylacetonate）（（tbt）_2Ir（acac））.Two kinds of materials of 4,7-diphenyl-1,10-phenanthroline（Bphen） and 1,3,5-tris（2-Nphenylbenzimidazolyl） benzene（TPBi） are selected as the electron transporting layer（ETL）,and the thickness of yellow EML is adjusted to optimize device performance.The device based on a 0.3-nm-thick yellow EML and Bphen exhibits high color stability with a slight Commission International de l＇Eclairage（CIE） coordinates variation of（0.017,0.009） at a luminance ranging from 52 cd/m^2 to 6998 cd/m^2.The TPBi-based device yields a high efficiency with a maximum external quantum efficiency（EQE）,current efficiency,and power efficiency of 10%,21.1 cd/A,and 21.3 lm/W,respectively.The ultrathin yellow EML suppresses hole trapping and short-radius Dexter energy transfer,so that Forster energy transfer（FRET）from DMAC-DPS to（tbt）_2Ir（acac） is dominant,which is beneficial to keep the color stable.The employment of TPBi with higher triplet excited state effectively alleviates the triplet exciton quenching by ETL to improve device efficiency.展开更多
The well crystalline YAG：Ce^3＋ phosphor was synthesized by sold-state method, and the temperature dependence of excitation and emission spectra of YAG：Ce^3＋ phosphor were investigated in the temperature range from...The well crystalline YAG：Ce^3＋ phosphor was synthesized by sold-state method, and the temperature dependence of excitation and emission spectra of YAG：Ce^3＋ phosphor were investigated in the temperature range from room temperature to 573 K. With temperature increasing, it was noted that the emission intensity of as-repared phosphors decreased considerably more rapidly when pumped by 460 nm than by 340 nm. The temperature-intensity curves under different excitation wavelengths were obtained using an Arrhenius function, and the corresponding activation energies were also obtained respectively. Thus, the experimental phenomenon was discussed in terms of nonradiative decay rate. The effects of as-prepared phosphors on the performance of the white LED with changing temperature were also studied.展开更多
Hydroponic farming is a viable and economical farming method,which can produce safe and healthy greens and vegetables conveniently and at a relatively low cost.It is essential to provide supplemental lighting for crop...Hydroponic farming is a viable and economical farming method,which can produce safe and healthy greens and vegetables conveniently and at a relatively low cost.It is essential to provide supplemental lighting for crops grown in greenhouses to meet the daily light requirement,Daily Light Integral(DLI).The present paper investigates how effectively and efficiently LEDs can be used as a light source in hydroponics.It is important for a hydroponic grower to assess the requirement of photo synthetically active radiation(PAR)or the Photosynthetic Photon Flux Density(PPFD),in a greenhouse,and adjust the quality and quantity of supplemental lighting accordingly.A Quantum sensor(or PAR sensor)can measure PAR more accurately than a digital light meter,which measures the light intensity or illuminance in the SI unit Lux,but a PAR sensor is relatively expensive and normally not affordable by an ordinary farmer.Therefore,based on the present investigation and experimental results,a very simple way to convert light intensity measured with a Lux meter into PAR is proposed,using a simple conversion factor(41.75 according to the present work).This allows a small-scale hydroponic farmer to use a simple and inexpensive technique to assess the day to day DLI values of PAR in a greenhouse accurately using just an inexpensive light meter.The present paper also proposes a more efficient way of using LED light panels in a hydroponic system.By moving the LED light panels closer to the crop,LED light source can use a fewer number of LEDs to produce the same required daily light requirement and can increase the efficiency of the power usage to more than 80%.Specifically,the present work has determined that it is important to design more efficient vertically movable LED light panels with capabilities of switching individual LEDs on and off,for the use in greenhouses.This allows a user to control the number of LEDs that can be lit at a particular time,as required.By doing so it is possible to increase the efficiency of a LED lighting system by reducing its cost of the electricity usage.展开更多
This paper presents a new compensation pixe] circuit suitable for active-matrix organic light-emitting diode （AMOLED） stereoscopic three dimensional （3D~ displays with shutter glasses. The simultaneous emissio~ met...This paper presents a new compensation pixe] circuit suitable for active-matrix organic light-emitting diode （AMOLED） stereoscopic three dimensional （3D~ displays with shutter glasses. The simultaneous emissio~ method was used to solve the crosstalk problem, in which the periods of initialization and threshold voltage detectio11 occur for each pixel of whole panel simultaneously. Furthermore, there was no need of the periods of initialization and threshold voltage detection from the second frame beginning by one-time detection method. employing threshold voltage The non-uniformity of the proposed pixel circuit was considerably low with an average value of 8.6% measured from 20 discrete proposed pixel circuits integrated by In-Zn-O thin film transistors （IZO TFTs）. It was shown that the OLED current almost remains constant for the number of frames up to 70 even the threshold voltage detection period only exists in the first frame.展开更多
Eu3+-activated Gd2(MoO4)3 pseudo-pompon-like red-emitting phosphors were prepared by solid-state method. The structure, morphology, and luminescent properties of these powder samples were investigated by X-ray diffrac...Eu3+-activated Gd2(MoO4)3 pseudo-pompon-like red-emitting phosphors were prepared by solid-state method. The structure, morphology, and luminescent properties of these powder samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and fluorescent spectrophotometry, respectively. The as-obtained phosphors were single crystalline phase with orthorhombic unit cell. The particles of the powder samples had the length of 5-12 m and width of 3-7 m with flake shape and large surface area, which is suitable for manufacture of white LEDs. The phosphor could be efficiently excited by the incident light of 348-425 nm, well matched with the output wavelength of near-UV (In,Ga)N chip, and re-emitted an intense red light peaking at 615 nm. By combing this phosphor with a ~395 nm-emitting (In,Ga)N chip, a red LED was fabricated, so that the applicability of this novel phosphor to white LEDs was confirmed. It is considered to be an efficient red-emitting conversion phosphor for solid-state lighting based on (In,Ga)N LEDs.展开更多
High cost of phosphors and significant efficiency roll-off at high brightness are the two main factors that limit the wide application of phosphorescent organic light-emitting diodes (PHOLEDs). Efforts have been paid ...High cost of phosphors and significant efficiency roll-off at high brightness are the two main factors that limit the wide application of phosphorescent organic light-emitting diodes (PHOLEDs). Efforts have been paid to find ways to reduce the phosphors’ concentration and efficiency roll-off of PHOLEDs. In this work, we reported red emission PHOLEDs with low dopant concentration and low efficiency roll-off based on a novel host material 2,4-biscyanophenyl-6-(12-phenylindole[2,3-a]carbazole-11-yl)-1,3,5-triazine (BCPICT), with thermally activated delayed fluorescent(TADF) properties. The device with 1.0% dopant concentration displayed a maximum external quantum efficiency of 10.7%.When the dopant concentration was increased to 2.0%, the device displayed a maximum external quantum efficiency of 10.5% and a low efficiency roll-off of 5.7% at 1000 cd/m2.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61675041 and 61605253)the Foundation for Innovation Research Groups of the National Natural Science Foundation of China(Grant No.61421002)the Science&Technology Department Program of Sichuan Province,China(Grant No.2016HH0027)
文摘Fluorescence/phosphorescence hybrid white organic light-emitting devices（WOLEDs） based on double emitting layers（EMLs） with high color stability are fabricated.The simplified EMLs consist of a non-doped blue thermally activated delayed fluorescence（TADF） layer using 9,9-dimethyl-9,10-dihydroacridine-diphenylsulfone（DMAC-DPS） and an ultrathin non-doped yellow phosphorescence layer employing bis[2-（4-tertbutylphenyl）benzothiazolato-N,C2＇]iridium（acetylacetonate）（（tbt）_2Ir（acac））.Two kinds of materials of 4,7-diphenyl-1,10-phenanthroline（Bphen） and 1,3,5-tris（2-Nphenylbenzimidazolyl） benzene（TPBi） are selected as the electron transporting layer（ETL）,and the thickness of yellow EML is adjusted to optimize device performance.The device based on a 0.3-nm-thick yellow EML and Bphen exhibits high color stability with a slight Commission International de l＇Eclairage（CIE） coordinates variation of（0.017,0.009） at a luminance ranging from 52 cd/m^2 to 6998 cd/m^2.The TPBi-based device yields a high efficiency with a maximum external quantum efficiency（EQE）,current efficiency,and power efficiency of 10%,21.1 cd/A,and 21.3 lm/W,respectively.The ultrathin yellow EML suppresses hole trapping and short-radius Dexter energy transfer,so that Forster energy transfer（FRET）from DMAC-DPS to（tbt）_2Ir（acac） is dominant,which is beneficial to keep the color stable.The employment of TPBi with higher triplet excited state effectively alleviates the triplet exciton quenching by ETL to improve device efficiency.
基金the Key Technologies R&D Program of Shandong Province (2006gg2201014)Tianjin Natural Science Foundation (07JCYBJC06400)Tianjin Education Committee Science and Technology Development Foundation
文摘The well crystalline YAG：Ce^3＋ phosphor was synthesized by sold-state method, and the temperature dependence of excitation and emission spectra of YAG：Ce^3＋ phosphor were investigated in the temperature range from room temperature to 573 K. With temperature increasing, it was noted that the emission intensity of as-repared phosphors decreased considerably more rapidly when pumped by 460 nm than by 340 nm. The temperature-intensity curves under different excitation wavelengths were obtained using an Arrhenius function, and the corresponding activation energies were also obtained respectively. Thus, the experimental phenomenon was discussed in terms of nonradiative decay rate. The effects of as-prepared phosphors on the performance of the white LED with changing temperature were also studied.
文摘Hydroponic farming is a viable and economical farming method,which can produce safe and healthy greens and vegetables conveniently and at a relatively low cost.It is essential to provide supplemental lighting for crops grown in greenhouses to meet the daily light requirement,Daily Light Integral(DLI).The present paper investigates how effectively and efficiently LEDs can be used as a light source in hydroponics.It is important for a hydroponic grower to assess the requirement of photo synthetically active radiation(PAR)or the Photosynthetic Photon Flux Density(PPFD),in a greenhouse,and adjust the quality and quantity of supplemental lighting accordingly.A Quantum sensor(or PAR sensor)can measure PAR more accurately than a digital light meter,which measures the light intensity or illuminance in the SI unit Lux,but a PAR sensor is relatively expensive and normally not affordable by an ordinary farmer.Therefore,based on the present investigation and experimental results,a very simple way to convert light intensity measured with a Lux meter into PAR is proposed,using a simple conversion factor(41.75 according to the present work).This allows a small-scale hydroponic farmer to use a simple and inexpensive technique to assess the day to day DLI values of PAR in a greenhouse accurately using just an inexpensive light meter.The present paper also proposes a more efficient way of using LED light panels in a hydroponic system.By moving the LED light panels closer to the crop,LED light source can use a fewer number of LEDs to produce the same required daily light requirement and can increase the efficiency of the power usage to more than 80%.Specifically,the present work has determined that it is important to design more efficient vertically movable LED light panels with capabilities of switching individual LEDs on and off,for the use in greenhouses.This allows a user to control the number of LEDs that can be lit at a particular time,as required.By doing so it is possible to increase the efficiency of a LED lighting system by reducing its cost of the electricity usage.
文摘This paper presents a new compensation pixe] circuit suitable for active-matrix organic light-emitting diode （AMOLED） stereoscopic three dimensional （3D~ displays with shutter glasses. The simultaneous emissio~ method was used to solve the crosstalk problem, in which the periods of initialization and threshold voltage detectio11 occur for each pixel of whole panel simultaneously. Furthermore, there was no need of the periods of initialization and threshold voltage detection from the second frame beginning by one-time detection method. employing threshold voltage The non-uniformity of the proposed pixel circuit was considerably low with an average value of 8.6% measured from 20 discrete proposed pixel circuits integrated by In-Zn-O thin film transistors （IZO TFTs）. It was shown that the OLED current almost remains constant for the number of frames up to 70 even the threshold voltage detection period only exists in the first frame.
基金Project supported by the Natural Science Research Project of the Jiangsu Higher Education Institutions (08KJD150014)the QingLan Project of the Jiangsu Province (2008)the Basic Research Fund of Jiangsu Teachers University of Technology (KYY09031)
文摘Eu3+-activated Gd2(MoO4)3 pseudo-pompon-like red-emitting phosphors were prepared by solid-state method. The structure, morphology, and luminescent properties of these powder samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and fluorescent spectrophotometry, respectively. The as-obtained phosphors were single crystalline phase with orthorhombic unit cell. The particles of the powder samples had the length of 5-12 m and width of 3-7 m with flake shape and large surface area, which is suitable for manufacture of white LEDs. The phosphor could be efficiently excited by the incident light of 348-425 nm, well matched with the output wavelength of near-UV (In,Ga)N chip, and re-emitted an intense red light peaking at 615 nm. By combing this phosphor with a ~395 nm-emitting (In,Ga)N chip, a red LED was fabricated, so that the applicability of this novel phosphor to white LEDs was confirmed. It is considered to be an efficient red-emitting conversion phosphor for solid-state lighting based on (In,Ga)N LEDs.
基金supported by the National Natural Science Foundation of China (51525304)the National Key Basic Research and Development Program of China (2015CB655002)
文摘High cost of phosphors and significant efficiency roll-off at high brightness are the two main factors that limit the wide application of phosphorescent organic light-emitting diodes (PHOLEDs). Efforts have been paid to find ways to reduce the phosphors’ concentration and efficiency roll-off of PHOLEDs. In this work, we reported red emission PHOLEDs with low dopant concentration and low efficiency roll-off based on a novel host material 2,4-biscyanophenyl-6-(12-phenylindole[2,3-a]carbazole-11-yl)-1,3,5-triazine (BCPICT), with thermally activated delayed fluorescent(TADF) properties. The device with 1.0% dopant concentration displayed a maximum external quantum efficiency of 10.7%.When the dopant concentration was increased to 2.0%, the device displayed a maximum external quantum efficiency of 10.5% and a low efficiency roll-off of 5.7% at 1000 cd/m2.
