South Africa strengthens its efforts in polar and ocean research Under the command of Ashley Johnson,the iron gate on the starboard side of the S.A.Agulhas II vessel opened slowly,and the paired bongo nets,supported b...South Africa strengthens its efforts in polar and ocean research Under the command of Ashley Johnson,the iron gate on the starboard side of the S.A.Agulhas II vessel opened slowly,and the paired bongo nets,supported by a mechanised framework,gradually sank 100 metres into the sea.After being towed for a while,they were retrieved,and scientists on board sampled the plankton collected for analysis.Simultaneously,the bongo nets also gathered data on temperature,salinity,conductivity,and depth.Following this,the scientists deployed Niskin bottles to collect water samples from various depths.展开更多
Achieving stable deep blue organic light emitting diodes(OLEDs)with narrow full width at half maximum(FWHM)and color gamut in the range of the commission International de L’Eclairage(CIE)ofy≤0.10 is still challengin...Achieving stable deep blue organic light emitting diodes(OLEDs)with narrow full width at half maximum(FWHM)and color gamut in the range of the commission International de L’Eclairage(CIE)ofy≤0.10 is still challenging in display and lighting applications.In this investigation,three donor-acceptor(D-A)deep-blue emitters were designed and synthesized via integrating asymmetric quinazoline(PQ)acceptor with weak donating carbazole(Cz)donor.The effect of the position and number of Cz group in PQunit are investigated,which is also first examples for syste matic research about the effect of different position of asymmetric PQ as acceptor on deep OLEDs.Their bandgaps of 3.12~3.19 eV and the singlet state energy levels of 3.12~3.19 eV were found to be sufficiently large to achieve deep blue light.As expected,these emitters-based OLEDs exhibit deep blue emission with the maximum wavelength≤450 nm and narrow FWHM≈60 nm.Especially,a CIE ofy=0.080 was achieved for 4 PQ-Cz-based OLED.Significantly,the deep blue electroluminescence(EL)spectra of these three emitters-based OLEDs are very stable and the corresponding CIE coordinates deviation(ΔCIE(x,y))can be negligible under the applied voltage ranging from 5 V to 9 V.展开更多
Phosphorescent and thermally activated delayed fluorescence(TADF)emitters can break through the spin statistics rules and achieve great success in external quantum efficiency(over 5%).However,maintaining high efficien...Phosphorescent and thermally activated delayed fluorescence(TADF)emitters can break through the spin statistics rules and achieve great success in external quantum efficiency(over 5%).However,maintaining high efficiency at high brightness is a tremendous challenge for applications of organic light emitting diodes.Hence,we reported two phenanthroimidazole derivatives PPI-An-CN and PPI-An-TP and achieved extremely low efficiency roll-off with about 99%of the maximum external quantum efficiency(EQEmax)maintained even at a high luminance of 1000 cd/cm2 based non-doped devices.When doping the two materials in CBP(4,4'-bis(N-carbazolyl)-1,1'-biphenyl),the doped devices still exhibited excellent stability at high brightness with CIEy≈0.07 and low turn-on voltage of only 2.8 V.The state-ofthe-art low efficiency roll-off makes the new materials attractive for potential applications.It is the first time that the Fragment Contribution Analysis method has been used to analyze the excited state properties of the molecules in the field of OLEDs,which helps us understand the mechanism more intuitively and deeply.展开更多
<div style="text-align:justify;"> An intracavity frequency doubling acousto-optically Q-switched Neodymium-doped Yttrium Orthvanadate (Nd:YVO<sub>4</sub>) 457 nm blue laser by employing a t...<div style="text-align:justify;"> An intracavity frequency doubling acousto-optically Q-switched Neodymium-doped Yttrium Orthvanadate (Nd:YVO<sub>4</sub>) 457 nm blue laser by employing a three-mirror folded cavity was demonstrated. With the incident pump power of 40.4 W, the maximum average output power of 439 mW 457 nm laser, and the minimum pulse duration of 86.14 ns and the maximum peak power of 510 W were achieved at 10 kHz. The M<sup>2</sup> factors are 1.23 and 1.61 in X and Y directions, respectively. The power stability in two hours is better than 2%. </div>展开更多
Achieving high-efficiency deep blue emitter with CIE_(y)<0.06(CIE,Commission Internationale de L’Eclairage)and external quantum efficiency(EQE)>10%has been a long-standing challenge for traditional fluorescent ...Achieving high-efficiency deep blue emitter with CIE_(y)<0.06(CIE,Commission Internationale de L’Eclairage)and external quantum efficiency(EQE)>10%has been a long-standing challenge for traditional fluorescent materials in organic light-emitting diodes(OLEDs).Here,we report the rational design and synthesis of two new deep blue luminogens:4-(10-(4’-(9 H-carbazol-9-yl)-2,5-dimethyl-[1,1’-biphe nyl]-4-yl)anthracen-9-yl)benzonitrile(2 M-ph-pCzAnBzt)and 4-(10-(4-(9 H-carbazol-9-yl)-2,5-dimethyl phenyl)anthracen-9-yl)benzonitrile(2 M-pCzAnBzt).In particular,2 M-ph-pCzAnBzt produces saturated deep blue emissions in a non-doped electroluminescent device with an exceptionally high EQE of 10.44% and CIE_(x,y)(0.151,0.057).The unprecedented electroluminescent efficiency is attributed to the combined effects of higher-order reversed intersystem crossing and triplet-triplet up-conversion,which are supported by analysis of theoretical calculation,triplet sensitization experiments,as well as nanosecond transient absorption spectroscopy.This research offers a new approach to resolve the shortage of high efficiency deep blue fluorescent emitters.展开更多
Bright tunable light emission in the short wavelength range from sulfur nanodots was demonstrated with a photoluminescence quantum yield(PLQY)of up to 59.4%.A fission-aggregation mechanism was proposed for the formati...Bright tunable light emission in the short wavelength range from sulfur nanodots was demonstrated with a photoluminescence quantum yield(PLQY)of up to 59.4%.A fission-aggregation mechanism was proposed for the formation of sulfur nanodots with desired performances.This synthetic strategy allowed for simultaneous size control from 3.2 to 5.6 nm,thus tuning the emission color from ultraviolet(UV)to deep blue(342±430 nm),and for the suppression of unwanted nonradiative recombination centers and deep level emission.The luminescence mechanism and quantum confinement effect of the synthesized sulfur nanodots were investigated by optical spectroscopy and theoretical calculations.These results show promise toward the application of sulfur nanodots in UV optoelectronics,biomedical treatments,and sterilization.展开更多
Hugo Shong explains what it takes to be a successful venture capitalist Hugo Shong, Vice Chairman of IDG Technology Venture Investment (IDGVC), is used to seeing 60-fold and sometimes 120-fold returns on investment.
It has been challenging to develop deep blue organic molecular fluorescent emitters with CIE y(y≤0.08)based on triplet-triplet annihilation(TTA). Here, we report facilely available dianthracenylphenylenebased emitter...It has been challenging to develop deep blue organic molecular fluorescent emitters with CIE y(y≤0.08)based on triplet-triplet annihilation(TTA). Here, we report facilely available dianthracenylphenylenebased emitters, which have a 3,5-di(4-t-butylphenyl)phenyl moiety at the one end and 4-cyanophenyl or 3-pyridyl at the other end, respectively. Both fluorophores show a high glass transition temperature of over 220℃ with a thermal decomposition temperature of over 430℃ at an initial weight loss of1%. The preliminary characterizations of the organic light-emitting diodes(OLEDs) that utilized these nondoped emitters provided high EQEs of 4.6%à5.9% with CIE coordinates(0.15, 0.07–0.08). The analysis of the EL transient decay revealed that TTA contributed to the observed performance. The results show that the new emitters are attractive as a potential TTA-based host to afford stable deep blue fluorescent OLEDs.展开更多
The control of the condensed superstructure of light-emitting conjugated polymers(LCPs)is a crucial factor to obtain high performance and stable organic optoelectronic devices.Side-chain engineering strategy is an eff...The control of the condensed superstructure of light-emitting conjugated polymers(LCPs)is a crucial factor to obtain high performance and stable organic optoelectronic devices.Side-chain engineering strategy is an effective platform to tune inter chain aggregation and photophysical behaviour of LCPs.Herein,we systematically investigated the alkyl-chain branched effecton the conformational transition and photophysical behaviour of polydiarylfluorenes toward efficient blue optoelectronic devices.The branched side chain will improve materials solubility to inhibit interchain aggregation in solution according to DLS and optical analysis,which is useful to obtain high quality film.Therefore,our branched PEODPF,POYDPF pristine film present high luminance efficiency of 36.1%and 39.6%,enhanced about 20%relative to that of PODPF.Compared to the liner-type sides'chain,these branched chains also suppress chain planarization and improve film morphological stability effectively.Interestingly,the branched polymer also had excellent stable amplified spontaneous emission(ASE)behaviour with low threshold(4.72μJ/cm2)and a center peak of 465 nm,even thermal annealing at 220℃in the air atmosphere.Therefore,side-chain branched strategy for LCPs is an effective means to control interchain aggregation,film morphology and photophysical property of LCPs.展开更多
Deep-blue perovskite light-emitting diodes(PeLEDs)based on reduced-dimensional perovskites(RDPs)still face a few challenges including severe trap-assisted nonradiative recombination,sluggish exciton transfer,and undes...Deep-blue perovskite light-emitting diodes(PeLEDs)based on reduced-dimensional perovskites(RDPs)still face a few challenges including severe trap-assisted nonradiative recombination,sluggish exciton transfer,and undesirable bathochromic shift of the electroluminescence spectra,impeding the realization of high-performance PeLEDs.Herein,an in situ chlorination(isCl)post-treatment strategy was employed to regulate phase reconstruction and renovate multiple defects of RDPs,leading to superior carrier cooling of 0.88 ps,extraordinary exciton binding energy of 122.53 meV,and higher photoluminescence quantum yield of 60.9%for RDP films with deep-blue emission at 450 nm.The phase regulation is accomplished via fluorine-derived hydrogen bonds that suppress the formation of small-n phases.Multiple defects,including halide vacancies(shallow-state defects)and lead-chloride antisite defects(deepstate defects),are renovated via C=O coordination and hydroxy-group-derived hydrogen bonds.Consequently,deepblue PeLEDs with a record maximum external quantum efficiency of 6.17%and stable electroluminescence at 454 nm were demonstrated,representing the best-performing deep-blue PeLEDs.展开更多
文摘South Africa strengthens its efforts in polar and ocean research Under the command of Ashley Johnson,the iron gate on the starboard side of the S.A.Agulhas II vessel opened slowly,and the paired bongo nets,supported by a mechanised framework,gradually sank 100 metres into the sea.After being towed for a while,they were retrieved,and scientists on board sampled the plankton collected for analysis.Simultaneously,the bongo nets also gathered data on temperature,salinity,conductivity,and depth.Following this,the scientists deployed Niskin bottles to collect water samples from various depths.
基金supports from the National Key Research and Development Plan(No.2016YFB0401004)supports from the Open Fund of Beijing National Laboratory for Molecular Sciences(BNLMS,No.BNLMS20160131)the Fundamental Research Funds for the Central Universities(Harbin Institute of Technology)。
文摘Achieving stable deep blue organic light emitting diodes(OLEDs)with narrow full width at half maximum(FWHM)and color gamut in the range of the commission International de L’Eclairage(CIE)ofy≤0.10 is still challenging in display and lighting applications.In this investigation,three donor-acceptor(D-A)deep-blue emitters were designed and synthesized via integrating asymmetric quinazoline(PQ)acceptor with weak donating carbazole(Cz)donor.The effect of the position and number of Cz group in PQunit are investigated,which is also first examples for syste matic research about the effect of different position of asymmetric PQ as acceptor on deep OLEDs.Their bandgaps of 3.12~3.19 eV and the singlet state energy levels of 3.12~3.19 eV were found to be sufficiently large to achieve deep blue light.As expected,these emitters-based OLEDs exhibit deep blue emission with the maximum wavelength≤450 nm and narrow FWHM≈60 nm.Especially,a CIE ofy=0.080 was achieved for 4 PQ-Cz-based OLED.Significantly,the deep blue electroluminescence(EL)spectra of these three emitters-based OLEDs are very stable and the corresponding CIE coordinates deviation(ΔCIE(x,y))can be negligible under the applied voltage ranging from 5 V to 9 V.
基金supported by the National Natural Science Foundation of China(No.51673113)the Key Project of DEGP(No.2018KZDXM032)
文摘Phosphorescent and thermally activated delayed fluorescence(TADF)emitters can break through the spin statistics rules and achieve great success in external quantum efficiency(over 5%).However,maintaining high efficiency at high brightness is a tremendous challenge for applications of organic light emitting diodes.Hence,we reported two phenanthroimidazole derivatives PPI-An-CN and PPI-An-TP and achieved extremely low efficiency roll-off with about 99%of the maximum external quantum efficiency(EQEmax)maintained even at a high luminance of 1000 cd/cm2 based non-doped devices.When doping the two materials in CBP(4,4'-bis(N-carbazolyl)-1,1'-biphenyl),the doped devices still exhibited excellent stability at high brightness with CIEy≈0.07 and low turn-on voltage of only 2.8 V.The state-ofthe-art low efficiency roll-off makes the new materials attractive for potential applications.It is the first time that the Fragment Contribution Analysis method has been used to analyze the excited state properties of the molecules in the field of OLEDs,which helps us understand the mechanism more intuitively and deeply.
文摘<div style="text-align:justify;"> An intracavity frequency doubling acousto-optically Q-switched Neodymium-doped Yttrium Orthvanadate (Nd:YVO<sub>4</sub>) 457 nm blue laser by employing a three-mirror folded cavity was demonstrated. With the incident pump power of 40.4 W, the maximum average output power of 439 mW 457 nm laser, and the minimum pulse duration of 86.14 ns and the maximum peak power of 510 W were achieved at 10 kHz. The M<sup>2</sup> factors are 1.23 and 1.61 in X and Y directions, respectively. The power stability in two hours is better than 2%. </div>
基金supported by the National Natural Science Foundation of China(62004074,51727809)the Science and Technology Department of Hubei Province(2019AAA063,2020BAA016)。
文摘Achieving high-efficiency deep blue emitter with CIE_(y)<0.06(CIE,Commission Internationale de L’Eclairage)and external quantum efficiency(EQE)>10%has been a long-standing challenge for traditional fluorescent materials in organic light-emitting diodes(OLEDs).Here,we report the rational design and synthesis of two new deep blue luminogens:4-(10-(4’-(9 H-carbazol-9-yl)-2,5-dimethyl-[1,1’-biphe nyl]-4-yl)anthracen-9-yl)benzonitrile(2 M-ph-pCzAnBzt)and 4-(10-(4-(9 H-carbazol-9-yl)-2,5-dimethyl phenyl)anthracen-9-yl)benzonitrile(2 M-pCzAnBzt).In particular,2 M-ph-pCzAnBzt produces saturated deep blue emissions in a non-doped electroluminescent device with an exceptionally high EQE of 10.44% and CIE_(x,y)(0.151,0.057).The unprecedented electroluminescent efficiency is attributed to the combined effects of higher-order reversed intersystem crossing and triplet-triplet up-conversion,which are supported by analysis of theoretical calculation,triplet sensitization experiments,as well as nanosecond transient absorption spectroscopy.This research offers a new approach to resolve the shortage of high efficiency deep blue fluorescent emitters.
基金financially supported by A*STAR(AME-IRG-A20E5c0083)the National Natural Science Foundation of China(52006005)。
文摘Bright tunable light emission in the short wavelength range from sulfur nanodots was demonstrated with a photoluminescence quantum yield(PLQY)of up to 59.4%.A fission-aggregation mechanism was proposed for the formation of sulfur nanodots with desired performances.This synthetic strategy allowed for simultaneous size control from 3.2 to 5.6 nm,thus tuning the emission color from ultraviolet(UV)to deep blue(342±430 nm),and for the suppression of unwanted nonradiative recombination centers and deep level emission.The luminescence mechanism and quantum confinement effect of the synthesized sulfur nanodots were investigated by optical spectroscopy and theoretical calculations.These results show promise toward the application of sulfur nanodots in UV optoelectronics,biomedical treatments,and sterilization.
文摘Hugo Shong explains what it takes to be a successful venture capitalist Hugo Shong, Vice Chairman of IDG Technology Venture Investment (IDGVC), is used to seeing 60-fold and sometimes 120-fold returns on investment.
基金supported by the National Key R&D Program of China(2016YFB0400701)NSFC-Guangdong Joint Program(U1801258 and U1301243)+2 种基金Department of Science and Technology of Guangdong Province(2017A050503002)Foundation of Guangzhou Science and Technology Project(201504010012)the support of Dongguan Major Special Project(2017215117010)
文摘It has been challenging to develop deep blue organic molecular fluorescent emitters with CIE y(y≤0.08)based on triplet-triplet annihilation(TTA). Here, we report facilely available dianthracenylphenylenebased emitters, which have a 3,5-di(4-t-butylphenyl)phenyl moiety at the one end and 4-cyanophenyl or 3-pyridyl at the other end, respectively. Both fluorophores show a high glass transition temperature of over 220℃ with a thermal decomposition temperature of over 430℃ at an initial weight loss of1%. The preliminary characterizations of the organic light-emitting diodes(OLEDs) that utilized these nondoped emitters provided high EQEs of 4.6%à5.9% with CIE coordinates(0.15, 0.07–0.08). The analysis of the EL transient decay revealed that TTA contributed to the observed performance. The results show that the new emitters are attractive as a potential TTA-based host to afford stable deep blue fluorescent OLEDs.
基金supported by the National Natural Science Foundation of China(Nos.61874053,21774061,91833306)Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions,PAPD(No.YX03002)+10 种基金the Six Peak Talents Foundation of Jiangsu Province(No.XCL-CXTD-009)Natural Science Funds of the Education Committee of Jiangsu Province(No.18KJA430009)"High-Level Talents in Six Industries"of Jiangsu Province(No.XYDXX-019)Program for Postgraduates Research Innovation in University of Jiangsu Province(No.KYCX17_0752)the open research fund from Key Laboratory for Organic Electronics and Information Display&and State Key Laboratory of Supramolecular Structure and Materials(No.sklssm2019017)Overseas Merit Foundation of Science and Technology of Nanjingfinancial support from the Regional Government of Madrid through NMAT2D-CM Project(No.S2018/NMT-4511)the Spanish Ministry of Economy and Competitiveness through project RTI2018-097508-B-I00through the Severo Ochoa Program for Centers of Excellence(No.SEV-2016-0686)the Campus of International Excellence(CEI)UAM+CSICthe China Scholarship Council(No.201608390023)for a PhD sponsorship
文摘The control of the condensed superstructure of light-emitting conjugated polymers(LCPs)is a crucial factor to obtain high performance and stable organic optoelectronic devices.Side-chain engineering strategy is an effective platform to tune inter chain aggregation and photophysical behaviour of LCPs.Herein,we systematically investigated the alkyl-chain branched effecton the conformational transition and photophysical behaviour of polydiarylfluorenes toward efficient blue optoelectronic devices.The branched side chain will improve materials solubility to inhibit interchain aggregation in solution according to DLS and optical analysis,which is useful to obtain high quality film.Therefore,our branched PEODPF,POYDPF pristine film present high luminance efficiency of 36.1%and 39.6%,enhanced about 20%relative to that of PODPF.Compared to the liner-type sides'chain,these branched chains also suppress chain planarization and improve film morphological stability effectively.Interestingly,the branched polymer also had excellent stable amplified spontaneous emission(ASE)behaviour with low threshold(4.72μJ/cm2)and a center peak of 465 nm,even thermal annealing at 220℃in the air atmosphere.Therefore,side-chain branched strategy for LCPs is an effective means to control interchain aggregation,film morphology and photophysical property of LCPs.
基金supported by the following grants:the National Youth Science Funds of China(Grant No.52302172)the Key Program of the National Natural Science Foundation of China(Grant No.52032004)+2 种基金the National Natural Science Foundation of China(Grant No.21902135,92056204)Y.B.Zhao would like to acknowledge the support of the National Natural Science Foundation of China(Grant No.61905206,12364054,and 11804294)Besides,we extend gratitude to the Theoretical and Computational Chemistry Team from Shiyanjia Lab for providing invaluable assistance(www.shiyanjia.com).
文摘Deep-blue perovskite light-emitting diodes(PeLEDs)based on reduced-dimensional perovskites(RDPs)still face a few challenges including severe trap-assisted nonradiative recombination,sluggish exciton transfer,and undesirable bathochromic shift of the electroluminescence spectra,impeding the realization of high-performance PeLEDs.Herein,an in situ chlorination(isCl)post-treatment strategy was employed to regulate phase reconstruction and renovate multiple defects of RDPs,leading to superior carrier cooling of 0.88 ps,extraordinary exciton binding energy of 122.53 meV,and higher photoluminescence quantum yield of 60.9%for RDP films with deep-blue emission at 450 nm.The phase regulation is accomplished via fluorine-derived hydrogen bonds that suppress the formation of small-n phases.Multiple defects,including halide vacancies(shallow-state defects)and lead-chloride antisite defects(deepstate defects),are renovated via C=O coordination and hydroxy-group-derived hydrogen bonds.Consequently,deepblue PeLEDs with a record maximum external quantum efficiency of 6.17%and stable electroluminescence at 454 nm were demonstrated,representing the best-performing deep-blue PeLEDs.
