Thermally activated delayed fluorescence(TADF)exciplexes,constituted of donor-acceptor moieties,have garnered mounting interest because of their promising potential to obtain high-performance electroluminescent device...Thermally activated delayed fluorescence(TADF)exciplexes,constituted of donor-acceptor moieties,have garnered mounting interest because of their promising potential to obtain high-performance electroluminescent devices.However,the moderate reverse intersystem crossing(RISC)of current reported exciplex systems and the lack of clear molecular design concepts to improve this situation have distinctly hindered the further use of exciplexes in organic light-emitting diodes(OLEDs).Herein,we conduct an exploration of exciplex systems founded upon[2,2]paracyclophane(PCP)-containing donor molecules and a triazine acceptor,which exhibit very fast RISC processes with a rate constant(k_(RISC))up to 8.3×10^(6) s^(-1)benefiting from the efficient interactions between the donor and acceptor fragments induced by the peripheral spatial-blocking of PCP group.Utilizing these deep-blue exciplexes as hosts and a multiple resonance(MR)molecule as emitter,pure-blue narrowband OLEDs with CIE coordinates of(0.124,0.137),a full-width at half-maximum(FWHM)of 23 nm,and a high external quantum efficiency(EQE)of around 30%are accessed.This study paves the way for developing blue OLEDs using PCP-based exciplex materials with an enhanced RISC process.展开更多
We investigated the formation of exciplex and electroluminescent absorption in ultraviolet organic light-emitting diodes（UV OLEDs） using different heterojunction structures.It is found that an energy barrier of over...We investigated the formation of exciplex and electroluminescent absorption in ultraviolet organic light-emitting diodes（UV OLEDs） using different heterojunction structures.It is found that an energy barrier of over 0.3 eV between the emissive layer（EML） and adjacent transport layer facilitates exciplex formation.The electron blocking layer effectively confines electrons in the EML,which contributes to pure UV emission and enhances efficiency.The change in EML thickness generates tunable UV emission from 376 nm to 406 nm.In addition,the UV emission excites low-energy organic function layers and produces photoluminescent emission.In UV OLED,avoiding the exciplex formation and averting light absorption can effectively improve the purity and efficiency.A maximum external quantum efficiency of 1.2%with a UV emission peak of 376 nm is realized.展开更多
Organic light-emitting diodes （OLEDs） composed of a novel fluorene derivative of 2,3-bis（9,9-dihexyl-9H-fluoren- 2-yl）-6,7-difluoroquinoxaline （F2Py） were fabricated, and exciplex emission was observed in the de...Organic light-emitting diodes （OLEDs） composed of a novel fluorene derivative of 2,3-bis（9,9-dihexyl-9H-fluoren- 2-yl）-6,7-difluoroquinoxaline （F2Py） were fabricated, and exciplex emission was observed in the device. To depress the exciplex in an OLED for pure colour light emission, 4, 4＇-N,N＇-dicarbazole-biphenyl （CBP） was inserted as a separator at the donor/acceptor interface. It was found that the device without the CBP layer emitted a green light peaking at 542 nm from the exciplex and a shoulder peak about 430 nm from F2Py. In contrast, the OLED with CBP layer emitted only a blue light peak at about 432 nm from F2Py. Device efficiencies were calculated by a simulative mode in an injection controlled type mechanism, and the results showed that exciplexes yield much lower quantum efficiency than excitons. The device with CBP has a higher power efficiency as no exciplex was present.展开更多
Two types of molecular and polymer devices employing (2-(4′-biphenyl)-5-(4″-tert-butylphenyl)-1,3,4-oxadiazole) (PBD) and poly(N-vinylcarbazole)(PVK) as electron transport and hole transport materials, respectively,...Two types of molecular and polymer devices employing (2-(4′-biphenyl)-5-(4″-tert-butylphenyl)-1,3,4-oxadiazole) (PBD) and poly(N-vinylcarbazole)(PVK) as electron transport and hole transport materials, respectively, have been fabricated. The structures of these two devices are ITO/PVK(70 nm)/PBD(60 nm)/Al and ITO/PVK∶PBD(1∶1 by mass, 70 nm)/Al. The formation of exciplex is evident by comparing the electroluminescence (EL) of a bi-layer device and the photoluminescence (PL) of a PVK and PBD mixed film. The maximum emission energy of exciplex evaluated is consistent with the peak emission of EL. Blue emissions from both devices are obtained. The type of exicplex is interpreted based on the energy level diagram of the bi-layer device.展开更多
The fluorescence behaviours of a new polymer poly [oxy-2 (4-N, N-dimethylaminobenzyl) propane-1 , 3-diyloxy-terephthaloyl] (Ⅰ) in solution were studied. Inter-and intra -molecular exciplex is formed between the singl...The fluorescence behaviours of a new polymer poly [oxy-2 (4-N, N-dimethylaminobenzyl) propane-1 , 3-diyloxy-terephthaloyl] (Ⅰ) in solution were studied. Inter-and intra -molecular exciplex is formed between the singlet excited state of N, N- dimethylanilino group (abbreviated to DMA) and the ground state of terephthalate group (abbreviated to TP). The intensity ratio of the long wavelength exciplex fluorescence to the short wavelength emission of DMA group is used as an index for the inter-and intra-molecular interaction of chromophores. The results are compared with model polymer polyoxy-2-(4-N ,N-dimethylaminobenzyl) propanc-1 , 3-diyloxyadipoyl (Ⅱ), model monomer compound 4-N, N-dimethylaminobenzylmethyl terephthalate(Ⅲ) and diethyl 2-( 4-N, N-dimethylaminobenzyl) malonate (Ⅳ). Polymer association derived by electron donor and acceptor interaction (EDA) is further verified as a key role in the interpolymer exciplex formation . The fluorescence decay time of (Ⅰ) and monomer (Ⅲ) are measured in solutions.展开更多
The bilayer organic light emitting devices （OLEDs） using two common aromatic diamines as hole transporting materials （HTMs） and BBOT （2,5-bis（5-tert-butyl-2-benzoxazolyl）thiophene） as electron transporting mat...The bilayer organic light emitting devices （OLEDs） using two common aromatic diamines as hole transporting materials （HTMs） and BBOT （2,5-bis（5-tert-butyl-2-benzoxazolyl）thiophene） as electron transporting material have been prepared, in which the electroluminescent spectra are different from the fluorescent spectra of each of the constituent materials. The electroluminescence is mainly attributed to exciplex confirmed by photoluminescence and electroluminescence measurements, and the type of exicplex is deternfined in terms of the energy level diagram of the bilayer devices, By comparing the molecular structures and energy levels of TPD and NPB, it is demonstrated that the structure of a molecule as well as its energy level has an effect on the exciplex formation.展开更多
Exciplex-emitters are attractive due to their distinct feature of easily achieving small singlet-triplet energy splitting for thermally activated delayed fluorescence(TADF),but face with challenges in convenient desig...Exciplex-emitters are attractive due to their distinct feature of easily achieving small singlet-triplet energy splitting for thermally activated delayed fluorescence(TADF),but face with challenges in convenient design of electron acceptors.New 9-phenylfluorene-based acceptor 9-[6-(2-cyano-7-isocyano-9-phenyl-9H-fluoren-9-yl)-9-ethyl-9H-carbazol-3-yl]-9-phenyl-9H-fluorene-2,7-dicarbonitrile(TriCNDPFCz)was designed and synthesized through tricyano-substitution.By mixing TriCNDPFCz with conventional donor 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane(TAPC),bright exciplex-TADF was obtained with a maximum current efficiency of 46.7 cd·A^(-1),power efficiency of 52.3 lm·W^(-1)and external quantum efficiency of 14.5%.The experimental characterizations indicate that tricyano-substitution in 9-phenylfluorene skeleton can form strong electron-accepting ability,which is useful and convenient for constructing electron acceptor in exciplex emission.展开更多
Gamma-cyclodextrin (γ-CD) was used to induce the formation of N,N-diethylaniline (DEA) exciplex in 15:85{φ=0.15)v/v EtOH-H_2O binary mixture.Measurements of the fluorescence spectra of anthracene in the presence or ...Gamma-cyclodextrin (γ-CD) was used to induce the formation of N,N-diethylaniline (DEA) exciplex in 15:85{φ=0.15)v/v EtOH-H_2O binary mixture.Measurements of the fluorescence spectra of anthracene in the presence or absence of DEA and γ-CD show that γ-CD can form 1:1:1 host/vip-Ⅰ/vip-Ⅱ inclusion complex with anthracene and DEA.展开更多
The color-tunable white organic light-emitting diode (CT-WOLED) with wide correlation color temperature (CCT) has many advantages in optimizing the artificial light source to adapt to the human physiological cycle. Th...The color-tunable white organic light-emitting diode (CT-WOLED) with wide correlation color temperature (CCT) has many advantages in optimizing the artificial light source to adapt to the human physiological cycle. The research on the change trend of CCT and the law of extending the change range of CCT will help to further improve the performance of this kind of device. The present work fabricated a series of CT-WOLED devices with a simple structure, which are all composed of two ultra-thin phosphor layers (PO-01 and Flrpic) and a spacer interlayer. The yellow interface exciplex (TCTA/PO-T2T) formed between the spacer layer (PO-T2T) and transmission material (TCTA) in EML will decrease the CCT value at low voltage. The relationship between the energy transfer in EML and CCT change trend is investigated by adjusting the interface exciplexes and the thickness of the interlayer or the phosphor layer in devices A, B and C, respectively. The results demonstrate that a simple OLED device with an interlayer inserted between two ultra-thin phosphor layers can achieve a wider CCT span from 3359 K to 6451 K at voltage increases from 2.75 V to 8.25 V. .展开更多
Developing single-pixel color-tunable electroluminescence technology represents a practical approach to circumvent current limitations in pixel processing and longevity.However,existing single-pixel color-tunable quan...Developing single-pixel color-tunable electroluminescence technology represents a practical approach to circumvent current limitations in pixel processing and longevity.However,existing single-pixel color-tunable quantum dot light-emitting diodes(QLEDs)devices predominantly employ complex tandem structures.Herein,we demonstrate single-layer color-tunable QLEDs by the real-time interface exciplex modulation with AgInZnS(AIZS)quantum dots(QDs).The dynamically color-tunable QLEDs based on green-and red-emitting AIZS QDs exhibit broad spectral coverage,spanning from green to blue,red to yellow,as well as standard white emission.The fabricated devices achieve a leading maximum external quantum efficiency of 5%for quaternary alloy AIZS-based QLEDs.Furthermore,we successfully demonstrate patterned and large-area QLEDs,systematically confirming their significant potential for application in full-color display and lighting technologies.展开更多
Magneto-conductance (MC) was used as a fingerprint detection tool to contactlessly visualize high-temperature evolution processes of exciplex (EX) states in theTBRb/C_(60) planar-heterojunction (PHJ) organic light-emi...Magneto-conductance (MC) was used as a fingerprint detection tool to contactlessly visualize high-temperature evolution processes of exciplex (EX) states in theTBRb/C_(60) planar-heterojunction (PHJ) organic light-emittingdiodes (OLEDs). Specifically, MC was used to contactlesslyobserve at room temperature around 300 K. The reverse intersystem crossing (RISC) process from triplet to singlet EXstates (EX_(3) → EX_(1)) in the device at 300 K is observed for thefirst time from the TBRb/C_(60) PHJ-OLED. The device shows ahalf-band-gap turn-on photoelectric characteristics. Temperature-dependentMC traces of the device present an interesting conversion from RISC to triplet-charge annihilation(TQA) process between EX_(3) and charge carriers (T_(1) + q → e + h+ q′) after the device temperature increasing from 300 to 425 Kvia in-situ heating. By comprehensively analyzing MC traces,current-voltage characteristic curves, transient electroluminescence spectra, and optical microscopy images of thedevice and atomic force microscopy images of the TBRb film,we find that the increase of temperature destroys the moleculestructures of organic materials, which leads to the generationof many traps inside the organic semiconductor films comprising the TBRb/C_(60) PHJ-OLED. These traps will capturepolaron-pairs, EX, and exciton states and then affect theirinteractions, which finally induces the changes of MC traces.This work not only deepens understandings of high-temperatureevolution processes of polaron-pairs, EX, and excitonstates in the TBRb/C_(60) PHJ devices, but also provides a newmethod to study the microscopic mechanisms in OLED operating in high temperature environment.展开更多
White organic light-emitting diodes(WOLEDs)have several desirable features,but their commercialization is hindered by the poor stability of blue light emitters and high production costs due to complicated device struc...White organic light-emitting diodes(WOLEDs)have several desirable features,but their commercialization is hindered by the poor stability of blue light emitters and high production costs due to complicated device structures.Herein,we investigate a standard blue emitting hole transporting material(HTM)N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine(NPB)and its exciplex emission upon combining with a suitable electron transporting material(ETM),3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole(TAZ).Blue and yellow OLEDs with simple device structures are developed by using a blend layer,NPB:TAZ,as a blue emitter as well as a host for yellow phosphorescent dopant iridium(III)bis(4-phenylthieno[3,2-c]pyridinato-N,C2')acetylacetonate(PO-01).Strategic device design then exploits the ambipolar charge transport properties of tetracene as a spacer layer to connect these blue and yellow emitting units.The tetracene-linked device demonstrates more promising results compared to those using a conventional charge generation layer(CGL).Judicious choice of the spacer prevents exciton difusion from the blue emitter unit,yet facilitates charge carrier transport to the yellow emitter unit to enable additional exciplex formation.This complementary behavior of the spacer improves the blue emission properties concomitantly yielding reasonable yellow emission.The overall white light emission properties are enhanced,achieving CIE coordinates(0.36,0.39)and color temperature(4643 K)similar to daylight.Employing intermolecular exciplex emission in OLEDs simplifes the device architecture via its dual functionality as a host and as an emitter.展开更多
High efficient yellow organic light emitting diodes （OLEDs） based on exciplex were reported. The exciplex was formed by 4, 4＇, 4″-tris β-methylphenyl （phenyi） amino]-triphenylamine （m-MTDATA） and 4, 7- diphen...High efficient yellow organic light emitting diodes （OLEDs） based on exciplex were reported. The exciplex was formed by 4, 4＇, 4″-tris β-methylphenyl （phenyi） amino]-triphenylamine （m-MTDATA） and 4, 7- diphenyl-1, 10-phenanthroline （BPhen）. The resulting yellow OLEDs exhibited an external quantum efficiency of over 7%, which is attributed to the effective energy back transfer from exciplex triplet state to exciplex singlet state. The maximum power efficiency of 25 lm/W was achieved. Doping a yellow phosphor Ir（bt）2（acac） into m-MTDATA： BPhen blend, a high efficiency device was achieved with a turn-on voltage of 2.1 V, maximum power efficiency and external quantum efficiency of 86.1 lm/W and 20.7%, respectively.展开更多
A novel acceptor material,9-(4′-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1′-biphenyl]-3-yl)-9H-carbazole(o-DTPPC)was developed to form interface exciplex with commonly used donors,to maximize the performances of red pho...A novel acceptor material,9-(4′-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1′-biphenyl]-3-yl)-9H-carbazole(o-DTPPC)was developed to form interface exciplex with commonly used donors,to maximize the performances of red phosphorescent organic light emitting diodes(PHOLEDs).It is found that the exciplex involving 4,4′-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline)(TAPC)exhibits the most significant thermally activated delayed fluorescence(TADF)property,derived from the high triplet energy level as well as strong hole-transporting ability of TAPC.Intriguingly,it is the same donor-acceptor combination which achieved the highest device efficiency when adopted as the host for red PHOLEDs.Maximum efficiencies as high as31.36 cd A^(-1),17.95 lm W^(-1),and 21.01%for the current efficiency,power efficiency and external quantum efficiency,respectively with low efficiency roll-off were realized.The improved performance can be attributed to the efficient TADF properties of the interface exciplex-forming host constituting TAPC,benefiting the F?rster energy transfer.The article first underlines the importance of the constituting molecules in the interface exciplex-forming hosts,shedding new insight about the choice of interface exciplex as the host for PHOLEDs,which may lead to even higher performances,paving their ways towards practical applications.展开更多
By connecting tercarbazole(3 Cz)and triphenyltriazine(TRz)units with a diphenyl ether group,we designed and synthesized a new donor-spacer-acceptor structure molecule9’-(4-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy)...By connecting tercarbazole(3 Cz)and triphenyltriazine(TRz)units with a diphenyl ether group,we designed and synthesized a new donor-spacer-acceptor structure molecule9’-(4-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy)phenyl)-9’H-9,3’:6’,9"-tercarbazole(3 Cz-o-TRz)as the multifunctional component of exciplex emitters.As expected,the intermolecular charge-transfer transition is dominant for3 Cz-o-TRz because of the space-enough and conjugation-forbidden linkage of the diphenyl ether group,increasing the intrinsic characteristics of the 3 Cz and TRz moieties in its single-molecule state.Accordingly,three common electron acceptors(4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine(B3 PyMPm),4,6-bis(3,5-di(pyridin-4-yl)phenyl)-2-methylpyrimidine(B4 PyMPm),and(1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1-diyl)tris(diphenylphosphineoxide)(POT2 T))and three common electron donors(4,4’-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline)(TAPC),tris(4-(10 H-phenoxazin-10-yl)phenyl)amine(TPA-PXZ),and N1-phenyl-N4,N4-bis(4-(phenyl(m-tolyl)amino)phenyl)-N1-(m-tolyl)benzene-1,4-diamine(m-MTDATA))were chosen to construct six exciplex emitters with 3 Cz-o-TRz.In the organic light-emitting diodes(OLEDs),the emission spectra of these exciplex emitters could be gradually modulated from 510 to 590 nm.In addition,TAPC:3 Cz-o-TRz-and 3 Cz-o-TRz:PO-T2 T-based OLEDs achieved desirable performance with maximum external quantum efficiencies(EQEs)around 12%.Moreover,a simple tandem OLED containing TAPC:3 Cz-o-TRz and 3 Czo-TRz:PO-T2 T emitters realized optimal performance with an ultralow turn-on voltage of 2.4 V and a maximum EQE of14.1%.These results indicate the great potential of the donorspacer-acceptor structure compounds in developing exciplex emitters.展开更多
An intramolecular excimer of poly(2- vinyl) naphthalene was formed by non-adjacentchromophores interaction, then a triple exciplex was formed by interaction with the acceptormolecule further in dilute solution. The li...An intramolecular excimer of poly(2- vinyl) naphthalene was formed by non-adjacentchromophores interaction, then a triple exciplex was formed by interaction with the acceptormolecule further in dilute solution. The lifetime of the intramolecular excimer of poly(2-vinyl) naphthalene, τ_2 = 18.83 ns and the rate constant for the triple exciplex formation,k_7 = 4. 18× 10~9 (mol/L)^(-1)s^(-1), under diffusion-control were measured. An excimer or anexciplex could be an intermediate of the triple exciplex formation. A theoretical model ofthe triple exciplex formation is proposed.展开更多
Triple exciplex formed between polyacenaphthalene and terephthalic dimethylester (TDE) has been studied by means of the steady-state and time-resolved fluorescence spectra. The theoretical model of the triple exciplex...Triple exciplex formed between polyacenaphthalene and terephthalic dimethylester (TDE) has been studied by means of the steady-state and time-resolved fluorescence spectra. The theoretical model of the triple exciplex formation for a flexible polymer chain in a dilute solution has been proposed. The fluorescence decays of the monomer, the exciplex and the triple exciplex obey a double exponential rule in the pbotophysical processes of the triple exciplex formation. The association rate constant of the exciplex formation is k_3=6.0×10~9s^(-1)(mol/L)^(-1); the association rate constant of the triple exciplex formation is k_6=5.2×10~7s^(-1). A mechanism for the triple exciplex formation from the exciplex to the triple exciplex has been proved through the noncrystal films corresponding to the same concentrations of the solution systems and the fluorescence lifetimes of the intramolecular excimer.展开更多
Both dimethyl terephthalate (DMTP) and dimethyl phthalate are able to form exciplex with 9-ethyl carbazole (EtCz) but the fluorescence quenching constant of DMTP to EtCz is larger than that of DMP to EtCz. The peak po...Both dimethyl terephthalate (DMTP) and dimethyl phthalate are able to form exciplex with 9-ethyl carbazole (EtCz) but the fluorescence quenching constant of DMTP to EtCz is larger than that of DMP to EtCz. The peak positions of the fluorescence bands of the exciplex formed from DMTP and DMP with EtCz are also different. The former gives a peak at shorter wavelength region. Either the exciplex formation rate constant k_3 or the exciplex dissociation rate constant k_4 is not alike. Both of these constants of DMTP are larger than those of DMP. All these results are difficult to explain with the established theory, so a new model which could be used to explain the results satisfactorily is supposed.展开更多
Effects of self-coiling of organic molecules on intramolecular exciplexformation of compound Ⅰ, in which the carbazole chromophore and terephthalic acid methylesteracceptor group are linked by one (CH_2)_(10) chain, ...Effects of self-coiling of organic molecules on intramolecular exciplexformation of compound Ⅰ, in which the carbazole chromophore and terephthalic acid methylesteracceptor group are linked by one (CH_2)_(10) chain, and the decrease of the fluorescence intensitiesof compounds Ⅱ, Ⅲ, and Ⅳ, in which the carbazole chromophore and 3, 5-dinitrobenzoate areconnected by one aliphatic chain of (CH_2)_(10) (Ⅱ), (CH_2)_(12) (Ⅲ), or (CH_2)_4 (Ⅳ), have beenstudied in the dioxane(DX)-H_2O binary system. The results show that self-coiling of organicmolecules in DX-H_2O facilitates intramolecular exciplex formation of Ⅰ and induces the decrease offluorescence intensities of Ⅱ, because of the proximity effect brought about by self-coiling oforganic molecules under hydrophobic-lipophilic interaction (HLI) between the excited carbazolechromophore and the acceptor. Since the similar effects are observed even when the concentrations ofthe probes are less than their CAgCs (critical aggregate concentrations) in the DX-H_2O mixturewith the same φ values, formation of the intermolecular exciplex has been excluded. The effects arefound to be strongly depended on φ values, indicating that they are mainly driven by HLI. Theproperties of the acceptors can also affect the intramolecular exciplex formation. With terephthalicacid methylester moiety as the acceptor, the carbazole chromophore exhibits the fluorescencespectra of the exciplex, while with 3, 5-dinitrobenzoate moiety as the acceptor, only thefluorescence spectra of excited carbazolyl chromophore are observed.展开更多
基金supported by the National Key R&D Program of China(2022YFE0109000)the National Natural Science Foundation of China(21975152,92256304,U23A20593)+1 种基金the China Postdoctoral Science Foundation(2022M722028)the Deutsche Forschungsgemeinschaft(DFG)under Germany’s Excellence Strategy(3DMM2O-EXC-2082/1-390761711)。
文摘Thermally activated delayed fluorescence(TADF)exciplexes,constituted of donor-acceptor moieties,have garnered mounting interest because of their promising potential to obtain high-performance electroluminescent devices.However,the moderate reverse intersystem crossing(RISC)of current reported exciplex systems and the lack of clear molecular design concepts to improve this situation have distinctly hindered the further use of exciplexes in organic light-emitting diodes(OLEDs).Herein,we conduct an exploration of exciplex systems founded upon[2,2]paracyclophane(PCP)-containing donor molecules and a triazine acceptor,which exhibit very fast RISC processes with a rate constant(k_(RISC))up to 8.3×10^(6) s^(-1)benefiting from the efficient interactions between the donor and acceptor fragments induced by the peripheral spatial-blocking of PCP group.Utilizing these deep-blue exciplexes as hosts and a multiple resonance(MR)molecule as emitter,pure-blue narrowband OLEDs with CIE coordinates of(0.124,0.137),a full-width at half-maximum(FWHM)of 23 nm,and a high external quantum efficiency(EQE)of around 30%are accessed.This study paves the way for developing blue OLEDs using PCP-based exciplex materials with an enhanced RISC process.
基金supported by the National Natural Science Foundation of China(Grant Nos.61136003 and 61275041)the Guangxi Provincial Natural Science Foundation,China(Grant No.2012GXNSFBA053168)
文摘We investigated the formation of exciplex and electroluminescent absorption in ultraviolet organic light-emitting diodes（UV OLEDs） using different heterojunction structures.It is found that an energy barrier of over 0.3 eV between the emissive layer（EML） and adjacent transport layer facilitates exciplex formation.The electron blocking layer effectively confines electrons in the EML,which contributes to pure UV emission and enhances efficiency.The change in EML thickness generates tunable UV emission from 376 nm to 406 nm.In addition,the UV emission excites low-energy organic function layers and produces photoluminescent emission.In UV OLED,avoiding the exciplex formation and averting light absorption can effectively improve the purity and efficiency.A maximum external quantum efficiency of 1.2%with a UV emission peak of 376 nm is realized.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60736005,60876051 and 60425101-1)the Young Talent Project of Sichuan Province of China(Grant No.09ZQ026-074)+2 种基金the Natural Science Foundation of Sichuan Province of China(Grant No.9140A02060609DZ0208)the Program for New Century Excellent Talents in University(Grant No.NCET-06-0812)the Special Research Foundation for Returned Overseas Scholars of the State Education Ministry (Grant No.GGRYJ08-05)
文摘Organic light-emitting diodes （OLEDs） composed of a novel fluorene derivative of 2,3-bis（9,9-dihexyl-9H-fluoren- 2-yl）-6,7-difluoroquinoxaline （F2Py） were fabricated, and exciplex emission was observed in the device. To depress the exciplex in an OLED for pure colour light emission, 4, 4＇-N,N＇-dicarbazole-biphenyl （CBP） was inserted as a separator at the donor/acceptor interface. It was found that the device without the CBP layer emitted a green light peaking at 542 nm from the exciplex and a shoulder peak about 430 nm from F2Py. In contrast, the OLED with CBP layer emitted only a blue light peak at about 432 nm from F2Py. Device efficiencies were calculated by a simulative mode in an injection controlled type mechanism, and the results showed that exciplexes yield much lower quantum efficiency than excitons. The device with CBP has a higher power efficiency as no exciplex was present.
文摘Two types of molecular and polymer devices employing (2-(4′-biphenyl)-5-(4″-tert-butylphenyl)-1,3,4-oxadiazole) (PBD) and poly(N-vinylcarbazole)(PVK) as electron transport and hole transport materials, respectively, have been fabricated. The structures of these two devices are ITO/PVK(70 nm)/PBD(60 nm)/Al and ITO/PVK∶PBD(1∶1 by mass, 70 nm)/Al. The formation of exciplex is evident by comparing the electroluminescence (EL) of a bi-layer device and the photoluminescence (PL) of a PVK and PBD mixed film. The maximum emission energy of exciplex evaluated is consistent with the peak emission of EL. Blue emissions from both devices are obtained. The type of exicplex is interpreted based on the energy level diagram of the bi-layer device.
文摘The fluorescence behaviours of a new polymer poly [oxy-2 (4-N, N-dimethylaminobenzyl) propane-1 , 3-diyloxy-terephthaloyl] (Ⅰ) in solution were studied. Inter-and intra -molecular exciplex is formed between the singlet excited state of N, N- dimethylanilino group (abbreviated to DMA) and the ground state of terephthalate group (abbreviated to TP). The intensity ratio of the long wavelength exciplex fluorescence to the short wavelength emission of DMA group is used as an index for the inter-and intra-molecular interaction of chromophores. The results are compared with model polymer polyoxy-2-(4-N ,N-dimethylaminobenzyl) propanc-1 , 3-diyloxyadipoyl (Ⅱ), model monomer compound 4-N, N-dimethylaminobenzylmethyl terephthalate(Ⅲ) and diethyl 2-( 4-N, N-dimethylaminobenzyl) malonate (Ⅳ). Polymer association derived by electron donor and acceptor interaction (EDA) is further verified as a key role in the interpolymer exciplex formation . The fluorescence decay time of (Ⅰ) and monomer (Ⅲ) are measured in solutions.
文摘The bilayer organic light emitting devices （OLEDs） using two common aromatic diamines as hole transporting materials （HTMs） and BBOT （2,5-bis（5-tert-butyl-2-benzoxazolyl）thiophene） as electron transporting material have been prepared, in which the electroluminescent spectra are different from the fluorescent spectra of each of the constituent materials. The electroluminescence is mainly attributed to exciplex confirmed by photoluminescence and electroluminescence measurements, and the type of exicplex is deternfined in terms of the energy level diagram of the bilayer devices, By comparing the molecular structures and energy levels of TPD and NPB, it is demonstrated that the structure of a molecule as well as its energy level has an effect on the exciplex formation.
文摘Exciplex-emitters are attractive due to their distinct feature of easily achieving small singlet-triplet energy splitting for thermally activated delayed fluorescence(TADF),but face with challenges in convenient design of electron acceptors.New 9-phenylfluorene-based acceptor 9-[6-(2-cyano-7-isocyano-9-phenyl-9H-fluoren-9-yl)-9-ethyl-9H-carbazol-3-yl]-9-phenyl-9H-fluorene-2,7-dicarbonitrile(TriCNDPFCz)was designed and synthesized through tricyano-substitution.By mixing TriCNDPFCz with conventional donor 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane(TAPC),bright exciplex-TADF was obtained with a maximum current efficiency of 46.7 cd·A^(-1),power efficiency of 52.3 lm·W^(-1)and external quantum efficiency of 14.5%.The experimental characterizations indicate that tricyano-substitution in 9-phenylfluorene skeleton can form strong electron-accepting ability,which is useful and convenient for constructing electron acceptor in exciplex emission.
文摘Gamma-cyclodextrin (γ-CD) was used to induce the formation of N,N-diethylaniline (DEA) exciplex in 15:85{φ=0.15)v/v EtOH-H_2O binary mixture.Measurements of the fluorescence spectra of anthracene in the presence or absence of DEA and γ-CD show that γ-CD can form 1:1:1 host/vip-Ⅰ/vip-Ⅱ inclusion complex with anthracene and DEA.
文摘The color-tunable white organic light-emitting diode (CT-WOLED) with wide correlation color temperature (CCT) has many advantages in optimizing the artificial light source to adapt to the human physiological cycle. The research on the change trend of CCT and the law of extending the change range of CCT will help to further improve the performance of this kind of device. The present work fabricated a series of CT-WOLED devices with a simple structure, which are all composed of two ultra-thin phosphor layers (PO-01 and Flrpic) and a spacer interlayer. The yellow interface exciplex (TCTA/PO-T2T) formed between the spacer layer (PO-T2T) and transmission material (TCTA) in EML will decrease the CCT value at low voltage. The relationship between the energy transfer in EML and CCT change trend is investigated by adjusting the interface exciplexes and the thickness of the interlayer or the phosphor layer in devices A, B and C, respectively. The results demonstrate that a simple OLED device with an interlayer inserted between two ultra-thin phosphor layers can achieve a wider CCT span from 3359 K to 6451 K at voltage increases from 2.75 V to 8.25 V. .
基金supported by the National Key Research and Development Program of China(2024YFB3612400 and 2024YFA1210002)the National Natural Science Foundation of China(62574111,62204120,52533012,U24A20286,52131304,and 62261160392)+1 种基金International Cooperation Program of Jiangsu Province of China(BZ2024038)the Fundamental Research Funds for the Central Universities(30925010415).
文摘Developing single-pixel color-tunable electroluminescence technology represents a practical approach to circumvent current limitations in pixel processing and longevity.However,existing single-pixel color-tunable quantum dot light-emitting diodes(QLEDs)devices predominantly employ complex tandem structures.Herein,we demonstrate single-layer color-tunable QLEDs by the real-time interface exciplex modulation with AgInZnS(AIZS)quantum dots(QDs).The dynamically color-tunable QLEDs based on green-and red-emitting AIZS QDs exhibit broad spectral coverage,spanning from green to blue,red to yellow,as well as standard white emission.The fabricated devices achieve a leading maximum external quantum efficiency of 5%for quaternary alloy AIZS-based QLEDs.Furthermore,we successfully demonstrate patterned and large-area QLEDs,systematically confirming their significant potential for application in full-color display and lighting technologies.
基金supported by the National Natural Science Foundations of China (12104076, 12474074)the National Science Foundation of Chongqing (CSTB2023NSCQ-MSX0207)+1 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission (KJQN202200569)the Basic Research Program (Science and Technology Fund) of Guizhou Provincial Science and Technology Department, Qiankeheji [2020] 1Y023。
文摘Magneto-conductance (MC) was used as a fingerprint detection tool to contactlessly visualize high-temperature evolution processes of exciplex (EX) states in theTBRb/C_(60) planar-heterojunction (PHJ) organic light-emittingdiodes (OLEDs). Specifically, MC was used to contactlesslyobserve at room temperature around 300 K. The reverse intersystem crossing (RISC) process from triplet to singlet EXstates (EX_(3) → EX_(1)) in the device at 300 K is observed for thefirst time from the TBRb/C_(60) PHJ-OLED. The device shows ahalf-band-gap turn-on photoelectric characteristics. Temperature-dependentMC traces of the device present an interesting conversion from RISC to triplet-charge annihilation(TQA) process between EX_(3) and charge carriers (T_(1) + q → e + h+ q′) after the device temperature increasing from 300 to 425 Kvia in-situ heating. By comprehensively analyzing MC traces,current-voltage characteristic curves, transient electroluminescence spectra, and optical microscopy images of thedevice and atomic force microscopy images of the TBRb film,we find that the increase of temperature destroys the moleculestructures of organic materials, which leads to the generationof many traps inside the organic semiconductor films comprising the TBRb/C_(60) PHJ-OLED. These traps will capturepolaron-pairs, EX, and exciton states and then affect theirinteractions, which finally induces the changes of MC traces.This work not only deepens understandings of high-temperatureevolution processes of polaron-pairs, EX, and excitonstates in the TBRb/C_(60) PHJ devices, but also provides a newmethod to study the microscopic mechanisms in OLED operating in high temperature environment.
基金support by DST-SERB,Govt.of India(CRG/2020/003699)CKV and KNNU acknowledge support from DST-AISRF program of the Department of Science and Technology,Government of India(DST/INT/AUS/P-74/2017)support from Council of Scientifc and Industrial Research(CSIR),Government of India for the award of a research fellowship.AKS acknowledges support from DST-INSPIRE for the award of a research fellowship.
文摘White organic light-emitting diodes(WOLEDs)have several desirable features,but their commercialization is hindered by the poor stability of blue light emitters and high production costs due to complicated device structures.Herein,we investigate a standard blue emitting hole transporting material(HTM)N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine(NPB)and its exciplex emission upon combining with a suitable electron transporting material(ETM),3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole(TAZ).Blue and yellow OLEDs with simple device structures are developed by using a blend layer,NPB:TAZ,as a blue emitter as well as a host for yellow phosphorescent dopant iridium(III)bis(4-phenylthieno[3,2-c]pyridinato-N,C2')acetylacetonate(PO-01).Strategic device design then exploits the ambipolar charge transport properties of tetracene as a spacer layer to connect these blue and yellow emitting units.The tetracene-linked device demonstrates more promising results compared to those using a conventional charge generation layer(CGL).Judicious choice of the spacer prevents exciton difusion from the blue emitter unit,yet facilitates charge carrier transport to the yellow emitter unit to enable additional exciplex formation.This complementary behavior of the spacer improves the blue emission properties concomitantly yielding reasonable yellow emission.The overall white light emission properties are enhanced,achieving CIE coordinates(0.36,0.39)and color temperature(4643 K)similar to daylight.Employing intermolecular exciplex emission in OLEDs simplifes the device architecture via its dual functionality as a host and as an emitter.
基金Acknowledgements We sincerely thank Y. Gu, C. L. Yang and H. Xu for their careful testing of the samples. The authors gratefully acknowledge the National Natural Science Foundation of China （Grant Nos. 51333007 and 50973104）, the National Basic Research Program of China （No. 2013CB834805）, the Foundation of Jilin Research Council （Nos.2012ZDGG001, 20130206003GX and 201105028）, and Chinese Academy of Sciences Instrument Project （No. YZ201103） for the support of this research.
文摘High efficient yellow organic light emitting diodes （OLEDs） based on exciplex were reported. The exciplex was formed by 4, 4＇, 4″-tris β-methylphenyl （phenyi） amino]-triphenylamine （m-MTDATA） and 4, 7- diphenyl-1, 10-phenanthroline （BPhen）. The resulting yellow OLEDs exhibited an external quantum efficiency of over 7%, which is attributed to the effective energy back transfer from exciplex triplet state to exciplex singlet state. The maximum power efficiency of 25 lm/W was achieved. Doping a yellow phosphor Ir（bt）2（acac） into m-MTDATA： BPhen blend, a high efficiency device was achieved with a turn-on voltage of 2.1 V, maximum power efficiency and external quantum efficiency of 86.1 lm/W and 20.7%, respectively.
基金supported by the National Key Basic Research and Development Program of China (2016YFB041003, 2016YFB0400702)the National Basic Research Program of China (2015CB655002)the National Natural Science Foundation of China (51525304, U1601651)
文摘A novel acceptor material,9-(4′-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1′-biphenyl]-3-yl)-9H-carbazole(o-DTPPC)was developed to form interface exciplex with commonly used donors,to maximize the performances of red phosphorescent organic light emitting diodes(PHOLEDs).It is found that the exciplex involving 4,4′-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline)(TAPC)exhibits the most significant thermally activated delayed fluorescence(TADF)property,derived from the high triplet energy level as well as strong hole-transporting ability of TAPC.Intriguingly,it is the same donor-acceptor combination which achieved the highest device efficiency when adopted as the host for red PHOLEDs.Maximum efficiencies as high as31.36 cd A^(-1),17.95 lm W^(-1),and 21.01%for the current efficiency,power efficiency and external quantum efficiency,respectively with low efficiency roll-off were realized.The improved performance can be attributed to the efficient TADF properties of the interface exciplex-forming host constituting TAPC,benefiting the F?rster energy transfer.The article first underlines the importance of the constituting molecules in the interface exciplex-forming hosts,shedding new insight about the choice of interface exciplex as the host for PHOLEDs,which may lead to even higher performances,paving their ways towards practical applications.
基金supported by the National Natural Science Foundation of China(51773029,52073040,51533005 and 51821002)the Fundamental Research Funds for the Central Universities(ZYGX2016Z010)the International Cooperation and Exchange Project of Science and Technology Department of Sichuan Province(2019YFH0057 and 2019YFH0059)。
文摘By connecting tercarbazole(3 Cz)and triphenyltriazine(TRz)units with a diphenyl ether group,we designed and synthesized a new donor-spacer-acceptor structure molecule9’-(4-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy)phenyl)-9’H-9,3’:6’,9"-tercarbazole(3 Cz-o-TRz)as the multifunctional component of exciplex emitters.As expected,the intermolecular charge-transfer transition is dominant for3 Cz-o-TRz because of the space-enough and conjugation-forbidden linkage of the diphenyl ether group,increasing the intrinsic characteristics of the 3 Cz and TRz moieties in its single-molecule state.Accordingly,three common electron acceptors(4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine(B3 PyMPm),4,6-bis(3,5-di(pyridin-4-yl)phenyl)-2-methylpyrimidine(B4 PyMPm),and(1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1-diyl)tris(diphenylphosphineoxide)(POT2 T))and three common electron donors(4,4’-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline)(TAPC),tris(4-(10 H-phenoxazin-10-yl)phenyl)amine(TPA-PXZ),and N1-phenyl-N4,N4-bis(4-(phenyl(m-tolyl)amino)phenyl)-N1-(m-tolyl)benzene-1,4-diamine(m-MTDATA))were chosen to construct six exciplex emitters with 3 Cz-o-TRz.In the organic light-emitting diodes(OLEDs),the emission spectra of these exciplex emitters could be gradually modulated from 510 to 590 nm.In addition,TAPC:3 Cz-o-TRz-and 3 Cz-o-TRz:PO-T2 T-based OLEDs achieved desirable performance with maximum external quantum efficiencies(EQEs)around 12%.Moreover,a simple tandem OLED containing TAPC:3 Cz-o-TRz and 3 Czo-TRz:PO-T2 T emitters realized optimal performance with an ultralow turn-on voltage of 2.4 V and a maximum EQE of14.1%.These results indicate the great potential of the donorspacer-acceptor structure compounds in developing exciplex emitters.
文摘An intramolecular excimer of poly(2- vinyl) naphthalene was formed by non-adjacentchromophores interaction, then a triple exciplex was formed by interaction with the acceptormolecule further in dilute solution. The lifetime of the intramolecular excimer of poly(2-vinyl) naphthalene, τ_2 = 18.83 ns and the rate constant for the triple exciplex formation,k_7 = 4. 18× 10~9 (mol/L)^(-1)s^(-1), under diffusion-control were measured. An excimer or anexciplex could be an intermediate of the triple exciplex formation. A theoretical model ofthe triple exciplex formation is proposed.
基金Project supported by the National Natural Science Foundation of China.
文摘Triple exciplex formed between polyacenaphthalene and terephthalic dimethylester (TDE) has been studied by means of the steady-state and time-resolved fluorescence spectra. The theoretical model of the triple exciplex formation for a flexible polymer chain in a dilute solution has been proposed. The fluorescence decays of the monomer, the exciplex and the triple exciplex obey a double exponential rule in the pbotophysical processes of the triple exciplex formation. The association rate constant of the exciplex formation is k_3=6.0×10~9s^(-1)(mol/L)^(-1); the association rate constant of the triple exciplex formation is k_6=5.2×10~7s^(-1). A mechanism for the triple exciplex formation from the exciplex to the triple exciplex has been proved through the noncrystal films corresponding to the same concentrations of the solution systems and the fluorescence lifetimes of the intramolecular excimer.
基金Project supported by the National Natural Science Foundation of China.
文摘Both dimethyl terephthalate (DMTP) and dimethyl phthalate are able to form exciplex with 9-ethyl carbazole (EtCz) but the fluorescence quenching constant of DMTP to EtCz is larger than that of DMP to EtCz. The peak positions of the fluorescence bands of the exciplex formed from DMTP and DMP with EtCz are also different. The former gives a peak at shorter wavelength region. Either the exciplex formation rate constant k_3 or the exciplex dissociation rate constant k_4 is not alike. Both of these constants of DMTP are larger than those of DMP. All these results are difficult to explain with the established theory, so a new model which could be used to explain the results satisfactorily is supposed.
基金theNationalNaturalScienceFoundationofChina (No .2 9972 0 5 2 ) theMinistryofScienceandTechnologyChineseAcademyofSciences
文摘Effects of self-coiling of organic molecules on intramolecular exciplexformation of compound Ⅰ, in which the carbazole chromophore and terephthalic acid methylesteracceptor group are linked by one (CH_2)_(10) chain, and the decrease of the fluorescence intensitiesof compounds Ⅱ, Ⅲ, and Ⅳ, in which the carbazole chromophore and 3, 5-dinitrobenzoate areconnected by one aliphatic chain of (CH_2)_(10) (Ⅱ), (CH_2)_(12) (Ⅲ), or (CH_2)_4 (Ⅳ), have beenstudied in the dioxane(DX)-H_2O binary system. The results show that self-coiling of organicmolecules in DX-H_2O facilitates intramolecular exciplex formation of Ⅰ and induces the decrease offluorescence intensities of Ⅱ, because of the proximity effect brought about by self-coiling oforganic molecules under hydrophobic-lipophilic interaction (HLI) between the excited carbazolechromophore and the acceptor. Since the similar effects are observed even when the concentrations ofthe probes are less than their CAgCs (critical aggregate concentrations) in the DX-H_2O mixturewith the same φ values, formation of the intermolecular exciplex has been excluded. The effects arefound to be strongly depended on φ values, indicating that they are mainly driven by HLI. Theproperties of the acceptors can also affect the intramolecular exciplex formation. With terephthalicacid methylester moiety as the acceptor, the carbazole chromophore exhibits the fluorescencespectra of the exciplex, while with 3, 5-dinitrobenzoate moiety as the acceptor, only thefluorescence spectra of excited carbazolyl chromophore are observed.
