The control of excited states and related emissive properties of gold(Ⅲ)complexes mainly depends on the modulation of intramolecular electronic interactions among gold(Ⅲ)metal center,chelating ligands and/or periphe...The control of excited states and related emissive properties of gold(Ⅲ)complexes mainly depends on the modulation of intramolecular electronic interactions among gold(Ⅲ)metal center,chelating ligands and/or peripheral groups.However,luminescent gold(Ⅲ)systems based on intermolecular electronic interactions have never been explored.Here we report a series of proof-of-concept gold(Ⅲ)exciplexes using a simple gold(Ⅲ)complex,AuDPPy,as an electron acceptor.The emissive properties of gold(Ⅲ)exciplexes can be regulated by combining AuDPPy with different donors.Inspiringly,these gold(Ⅲ)exciplexes have donor-dependent emission mechanisms:dominant phosphorescence or dual radiative channels of thermally activated delayed fluorescence(TADF)and phosphorescence.Consequently,these gold(Ⅲ)exciplexes deliver green-to-red electroluminescence with external quantum efficiencies(EQEs)of up to 10.1%.More importantly,using these gold(Ⅲ)exciplexes to host multi-resonance TADF emitters results in narrowband yellow,orange,and deep-red electroluminescence with high EQEs of 23.5%,24.4%,and 27.4%,respectively,competitive to the highest values for gold(Ⅲ)OLEDs in similar color gamut.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
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
The photoluminescent (PL) and electroluminescent (EL) properties of a series of ligand emitting rare earth complexes (including Y^(3+), La^(3+), Gd^(3+) and Lu^(3+)) were systematically studied. These complexes have t...The photoluminescent (PL) and electroluminescent (EL) properties of a series of ligand emitting rare earth complexes (including Y^(3+), La^(3+), Gd^(3+) and Lu^(3+)) were systematically studied. These complexes have the same anionic ligand, 1-phenyl-3-methyl-4-isobutyryl-5-pyrazoloneate (PMIP), and three neutral ligands, triphenyl phosphine oxide (TPPO), 2, 2′-dipyridine (Bipy) and phenanthroline (Phen). Measured with 60 nm thin film of these complexes vaporized in vacuum on quartz substrates, a good regularity in the PL properties was observed. For rational comparison, the same structural EL devices based on these complexes, ITO/PVK (40 nm)/the complex (80 nm)/Mg: Ag (200 nm)/Ag (100 nm), were fabricated. Excluding the exciplex emission happens, the EL luminance usually increases with the increasing of PL efficiency.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
A series of organic photovoltaic (PV) cells in which the electron acceptor and donor are gadolinium (dibenzoylmethanato)_3(bathophenanthroline) [Gd(DBM)_3bath] and N,N′-diphenyl-N,N′bis(3-methylphenyl)-1,1′-dipheny...A series of organic photovoltaic (PV) cells in which the electron acceptor and donor are gadolinium (dibenzoylmethanato)_3(bathophenanthroline) [Gd(DBM)_3bath] and N,N′-diphenyl-N,N′bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine [TPD], respectively, were fabricated. Although TPD acts as an active layer in the bilayered cells, insertion of a Gd-complex film between TPD and the alloy cathode is necessary for efficient carrier photogeneration. Open-circuit voltage of 3.2 V was obtained due to efficient exciton dissociation near the interface between Gd(DBM)_3bath and TPD. By incorporating an ultrathin mixed layer of Gd-complex and TPD, external quantum efficiency is improved significantly. Photovoltaic performance of the devices has a common origin, exciplex formation, which results in broadband emission during both photoluminescent and the electroluminescent processes.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
We fabricate a kind of novel efficient blue fluorescent organic light emitting device（OLED） based on p-n heterojunctions composed of hole transporting layer（HTL） N,N ＇-bis（naphthalen-1-yl）-N,N ＇-bis（phenyl）-...We fabricate a kind of novel efficient blue fluorescent organic light emitting device（OLED） based on p-n heterojunctions composed of hole transporting layer（HTL） N,N ＇-bis（naphthalen-1-yl）-N,N ＇-bis（phenyl）-benzidine（NPB） and electron transporting layer（ETL） 4,7-diphnenyl-1,10-phenanthroline（BPhen）,into which a new blue material,DNCA（a derivation of N 6,N 6,N 12,N 12-tetrap-tolylchrysene-6,12-diamine）,is partially doped simultaneously,and double emitting layers are configured.With a turn-on voltage of 2.6 V at 1 cd/m 2,this type of OLED presents a maximum luminance efficiency（η max） of 8.83 cd/A at 5.818 mA/cm 2 and a maximum luminance of over 40000 cd/m 2.Meanwhile,the Commission Internationale De L＇Eclairage（CIE） coordinates of this device change slightly from（0.13,0.27） to（0.13,0.23） as the driving voltage increases from 3 V to 11 V.This improvement in the electroluminescent characteristics is attributed mainly to the ideal p-n heterojunction which can confine and distribute excitons evenly on two sides of the heterojunction interface so as to improve the carrier combination rate and expand the light-emitting region.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
A vinyl monomer having an electron-donating moiety, p-(N,N-dimethylamino)styrenc (DMAS),was synthesized. It was combined with benzoyl peroxide (BPO) to form a redox initiation system to initiatethe polymerization of m...A vinyl monomer having an electron-donating moiety, p-(N,N-dimethylamino)styrenc (DMAS),was synthesized. It was combined with benzoyl peroxide (BPO) to form a redox initiation system to initiatethe polymerization of methyl methacrylate (MMA). UV spectra measurements show that DMAS enters thePMMA chain as well. Both DMAS and its polymer P(DMAS) display strong fluorescence, and thefluorescence can be quenched by electron-deficient compounds such as methacrylonitrile, fumaronitrile andmethyl methacrylate etc. Moreover, DMAS can also form charge transfer complex (CTC) with strongelectron acceptors such as tetracyanoethylene (TCNE). The difference between the photochemical propertiesof DMAS and P(DMAS) were explained in terms of molecular structure change and polymer conformationeffect in solution. In addition, the CTC and exciplex formation of DMAS or P(DMAS) with C_(60) were alsostudied.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
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
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 stable spectrum can be obtained when the voltage changes, which is a necessary condition for the white organic light emitting diode (WOLED) device to be widely used in the field of solid-state lighting. However, w...The stable spectrum can be obtained when the voltage changes, which is a necessary condition for the white organic light emitting diode (WOLED) device to be widely used in the field of solid-state lighting. However, with the increase of voltage, the movement of the recombination zone (RZ) is inevitable because the perfect bipolar host material is difficult to obtain, which will redistribute the energy in the light emitting layer (EML) and affect the stability of the spectrum. We fabricate a series of ternary hybrid WOLEDs with a simple structure by inserting ultra-thin PO-T2T into the blue exciplex (TCTA:TPBi) to form the green interface exciplex. Without considering the movement of RZ, device B2 realizes the dynamic balance energy distribution in EML and stable spectrum by controlling two processes of the Dexter energy transfer and exciton capture. By modifying the doping ratio of the host material, we also find that the broadened RZ is helpful to further improve the spectral stability of the device. When the voltage changes from 3 V to 7 V, the change range of color coordinates is only (0.026, 0.025).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
Pure organic room-temperature phosphorescence(RTP)has drawn broad attention due to its long persistent luminescence and large Stokes shift.Although the doping strategy has become one of the most effective methods to c...Pure organic room-temperature phosphorescence(RTP)has drawn broad attention due to its long persistent luminescence and large Stokes shift.Although the doping strategy has become one of the most effective methods to construct organic RTP systems,there is still some fuzziness of impurities,mechanisms and luminescence regulation.This study develops a series of doping RTP systems based on exciplex,in which BPC@PPZ(where BPC is N-(4-bromophenyl)-carbazole,PPZ is 10-phenyl-10H-phenothiazine)achieved the highest quantum yield of 36.3%,while BPC@CE(where CE is coronene)showed the longest lifetime of 628.5 ms.The relevant data verify the mechanism that RTP comes from the charge transfer(CT)state of exciplex.Further,the introduction of Nile Red into the exciplex system results in the triple-singlet F?rster resonance energy transfer,exhibiting a red delayed fluorescence.Besides,when incorporating the coumarin derivatives into doping system,distinct ^(1)CT*&^(3)CT*states are generated through the CT process,accompanying a brand-new long persistent luminescence excited by visible light.These findings present an approach to regulate the CT state for achieving different persistent luminescence in the multicomponent system.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
4,7-Bisphenyl-1,10-phenanthroline(BPhen)is a promising electron transport material(ETM)and has been widely used in organic light-emitting diodes(OLEDs)because of the large electron mobility and easy fabrication proces...4,7-Bisphenyl-1,10-phenanthroline(BPhen)is a promising electron transport material(ETM)and has been widely used in organic light-emitting diodes(OLEDs)because of the large electron mobility and easy fabrication process.However,its low glass transition temperature would lead to poor device stability.In the past decades,various attempts have been carried out to improve its thermal stability though always be accomplished by the reduced electron mobility.Here,we present a molecular engineering to modulate the properties of BPhen,and through which,a versatile BPhen derivative(4,7-bis(naphthaleneb-yl)-1,10-phenanthroline,b-BNPhen)with high thermal stability(glass transition temperature=111.9℃),large electron mobility(7.8×10-4 cm2/(V s)under an electrical field of 4.5×105 V/cm)and excellent n-doping ability with an air-stable metal of Ag is developed and used as multifunctional layers to improve the efficiency and enhance the stability of OLEDs.This work elucidates the great importance of our molecular engineering methodology and device structure optimization strategy,unlocking the potential of 1,10-phenanthroline derivatives towards practical applications.展开更多
Metal-free room-temperature phosphorescence(RTP)materials have the characteristics of large Stokes shift,long lifetime,and triplet state transition.They exhibit application potential in various fields,such as bioimagi...Metal-free room-temperature phosphorescence(RTP)materials have the characteristics of large Stokes shift,long lifetime,and triplet state transition.They exhibit application potential in various fields,such as bioimaging,computer display,sensor,and anticounterfeiting and have drawn much research interest.Recent work showed that manipulating intermolecular interactions(e.g.,crystallization,polymerization,and rigid matrix)and host-vip assembly to restrain nonradiative transitions and isolate phosphor from oxygen as much as possible is a feasible way to obtain various types of efficient RTP materials.In some cases,intermolecular interactions also facilitated RTP emission by regulating the triplet state.On the other hand,heavy atoms(Br,I,etc.),heteroatoms(N,O,S,etc.),or carbonyls were introduced to the molecular skeleton through molecular engineering to enhance intersystem crossing,which is important for populating the triplet exciton.By comprehensively using the aforesaid strategies,great progress has been made for RTP materials.In this mini-review,we summarized recent advances in organic RTP materials based on manipulating intermolecular interactions.Typical host-vip assembly,hydrogen-bond assembly,energy transfer process,and exciplex emission system-based RTP materials were well illustrated.In summary,the current challenges and prospects for development in this field were presented.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
基金supported by the National Natural Science Foundation of China(52022071,52130308)Shenzhen Fundamental Research Program(JCYJ20190808151209557,ZDSYS20210623091813040)。
文摘The control of excited states and related emissive properties of gold(Ⅲ)complexes mainly depends on the modulation of intramolecular electronic interactions among gold(Ⅲ)metal center,chelating ligands and/or peripheral groups.However,luminescent gold(Ⅲ)systems based on intermolecular electronic interactions have never been explored.Here we report a series of proof-of-concept gold(Ⅲ)exciplexes using a simple gold(Ⅲ)complex,AuDPPy,as an electron acceptor.The emissive properties of gold(Ⅲ)exciplexes can be regulated by combining AuDPPy with different donors.Inspiringly,these gold(Ⅲ)exciplexes have donor-dependent emission mechanisms:dominant phosphorescence or dual radiative channels of thermally activated delayed fluorescence(TADF)and phosphorescence.Consequently,these gold(Ⅲ)exciplexes deliver green-to-red electroluminescence with external quantum efficiencies(EQEs)of up to 10.1%.More importantly,using these gold(Ⅲ)exciplexes to host multi-resonance TADF emitters results in narrowband yellow,orange,and deep-red electroluminescence with high EQEs of 23.5%,24.4%,and 27.4%,respectively,competitive to the highest values for gold(Ⅲ)OLEDs in similar color gamut.
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.
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.
文摘The photoluminescent (PL) and electroluminescent (EL) properties of a series of ligand emitting rare earth complexes (including Y^(3+), La^(3+), Gd^(3+) and Lu^(3+)) were systematically studied. These complexes have the same anionic ligand, 1-phenyl-3-methyl-4-isobutyryl-5-pyrazoloneate (PMIP), and three neutral ligands, triphenyl phosphine oxide (TPPO), 2, 2′-dipyridine (Bipy) and phenanthroline (Phen). Measured with 60 nm thin film of these complexes vaporized in vacuum on quartz substrates, a good regularity in the PL properties was observed. For rational comparison, the same structural EL devices based on these complexes, ITO/PVK (40 nm)/the complex (80 nm)/Mg: Ag (200 nm)/Ag (100 nm), were fabricated. Excluding the exciplex emission happens, the EL luminance usually increases with the increasing of PL efficiency.
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A series of organic photovoltaic (PV) cells in which the electron acceptor and donor are gadolinium (dibenzoylmethanato)_3(bathophenanthroline) [Gd(DBM)_3bath] and N,N′-diphenyl-N,N′bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine [TPD], respectively, were fabricated. Although TPD acts as an active layer in the bilayered cells, insertion of a Gd-complex film between TPD and the alloy cathode is necessary for efficient carrier photogeneration. Open-circuit voltage of 3.2 V was obtained due to efficient exciton dissociation near the interface between Gd(DBM)_3bath and TPD. By incorporating an ultrathin mixed layer of Gd-complex and TPD, external quantum efficiency is improved significantly. Photovoltaic performance of the devices has a common origin, exciplex formation, which results in broadband emission during both photoluminescent and the electroluminescent processes.
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.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60906022 and 60876046)the Tianjin Natural Science Foundation,China (Grant No. 10JCYBJC01100)
文摘We fabricate a kind of novel efficient blue fluorescent organic light emitting device（OLED） based on p-n heterojunctions composed of hole transporting layer（HTL） N,N ＇-bis（naphthalen-1-yl）-N,N ＇-bis（phenyl）-benzidine（NPB） and electron transporting layer（ETL） 4,7-diphnenyl-1,10-phenanthroline（BPhen）,into which a new blue material,DNCA（a derivation of N 6,N 6,N 12,N 12-tetrap-tolylchrysene-6,12-diamine）,is partially doped simultaneously,and double emitting layers are configured.With a turn-on voltage of 2.6 V at 1 cd/m 2,this type of OLED presents a maximum luminance efficiency（η max） of 8.83 cd/A at 5.818 mA/cm 2 and a maximum luminance of over 40000 cd/m 2.Meanwhile,the Commission Internationale De L＇Eclairage（CIE） coordinates of this device change slightly from（0.13,0.27） to（0.13,0.23） as the driving voltage increases from 3 V to 11 V.This improvement in the electroluminescent characteristics is attributed mainly to the ideal p-n heterojunction which can confine and distribute excitons evenly on two sides of the heterojunction interface so as to improve the carrier combination rate and expand the light-emitting region.
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.
基金This project was supported by the National Natural Science Foundation of China.
文摘A vinyl monomer having an electron-donating moiety, p-(N,N-dimethylamino)styrenc (DMAS),was synthesized. It was combined with benzoyl peroxide (BPO) to form a redox initiation system to initiatethe polymerization of methyl methacrylate (MMA). UV spectra measurements show that DMAS enters thePMMA chain as well. Both DMAS and its polymer P(DMAS) display strong fluorescence, and thefluorescence can be quenched by electron-deficient compounds such as methacrylonitrile, fumaronitrile andmethyl methacrylate etc. Moreover, DMAS can also form charge transfer complex (CTC) with strongelectron acceptors such as tetracyanoethylene (TCNE). The difference between the photochemical propertiesof DMAS and P(DMAS) were explained in terms of molecular structure change and polymer conformationeffect in solution. In addition, the CTC and exciplex formation of DMAS or P(DMAS) with C_(60) were alsostudied.
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 stable spectrum can be obtained when the voltage changes, which is a necessary condition for the white organic light emitting diode (WOLED) device to be widely used in the field of solid-state lighting. However, with the increase of voltage, the movement of the recombination zone (RZ) is inevitable because the perfect bipolar host material is difficult to obtain, which will redistribute the energy in the light emitting layer (EML) and affect the stability of the spectrum. We fabricate a series of ternary hybrid WOLEDs with a simple structure by inserting ultra-thin PO-T2T into the blue exciplex (TCTA:TPBi) to form the green interface exciplex. Without considering the movement of RZ, device B2 realizes the dynamic balance energy distribution in EML and stable spectrum by controlling two processes of the Dexter energy transfer and exciton capture. By modifying the doping ratio of the host material, we also find that the broadened RZ is helpful to further improve the spectral stability of the device. When the voltage changes from 3 V to 7 V, the change range of color coordinates is only (0.026, 0.025).
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(2022YFB3203500)the National Natural Science Foundation of China(22125803,T2488302,22020102006,22205062)+2 种基金the Science and Technology Commission of Shanghai Municipality(24DX1400200)the Guangxi Department of Science and Technology(AA23062016)the Fundamental Research Funds for the Central Universities。
文摘Pure organic room-temperature phosphorescence(RTP)has drawn broad attention due to its long persistent luminescence and large Stokes shift.Although the doping strategy has become one of the most effective methods to construct organic RTP systems,there is still some fuzziness of impurities,mechanisms and luminescence regulation.This study develops a series of doping RTP systems based on exciplex,in which BPC@PPZ(where BPC is N-(4-bromophenyl)-carbazole,PPZ is 10-phenyl-10H-phenothiazine)achieved the highest quantum yield of 36.3%,while BPC@CE(where CE is coronene)showed the longest lifetime of 628.5 ms.The relevant data verify the mechanism that RTP comes from the charge transfer(CT)state of exciplex.Further,the introduction of Nile Red into the exciplex system results in the triple-singlet F?rster resonance energy transfer,exhibiting a red delayed fluorescence.Besides,when incorporating the coumarin derivatives into doping system,distinct ^(1)CT*&^(3)CT*states are generated through the CT process,accompanying a brand-new long persistent luminescence excited by visible light.These findings present an approach to regulate the CT state for achieving different persistent luminescence in the multicomponent system.
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supported by the National Key Basic Research and Development Program of China(2017YFA0204501,2016YFB0400702 and 2016YFB0401003)the National Natural Science Foundation of China(51525304 and 61890942)the Fundamental Research Funds for the Central Universities.
文摘4,7-Bisphenyl-1,10-phenanthroline(BPhen)is a promising electron transport material(ETM)and has been widely used in organic light-emitting diodes(OLEDs)because of the large electron mobility and easy fabrication process.However,its low glass transition temperature would lead to poor device stability.In the past decades,various attempts have been carried out to improve its thermal stability though always be accomplished by the reduced electron mobility.Here,we present a molecular engineering to modulate the properties of BPhen,and through which,a versatile BPhen derivative(4,7-bis(naphthaleneb-yl)-1,10-phenanthroline,b-BNPhen)with high thermal stability(glass transition temperature=111.9℃),large electron mobility(7.8×10-4 cm2/(V s)under an electrical field of 4.5×105 V/cm)and excellent n-doping ability with an air-stable metal of Ag is developed and used as multifunctional layers to improve the efficiency and enhance the stability of OLEDs.This work elucidates the great importance of our molecular engineering methodology and device structure optimization strategy,unlocking the potential of 1,10-phenanthroline derivatives towards practical applications.
基金supported by the National Natural Science Foundation of China(21788102,22125803,22020102006,21871083)Shanghai Municipal Science and Technology Major Project(2018SHZDZX03)+3 种基金the Program of Shanghai Academic/Technology Research Leader(20XD1421300)the“Shu Guang”Project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation(19SG26)the Fundamental Research Funds for the Central Universitiesthe China National Postdoctoral Program for Innovative Talents(BX20220106)。
文摘Metal-free room-temperature phosphorescence(RTP)materials have the characteristics of large Stokes shift,long lifetime,and triplet state transition.They exhibit application potential in various fields,such as bioimaging,computer display,sensor,and anticounterfeiting and have drawn much research interest.Recent work showed that manipulating intermolecular interactions(e.g.,crystallization,polymerization,and rigid matrix)and host-vip assembly to restrain nonradiative transitions and isolate phosphor from oxygen as much as possible is a feasible way to obtain various types of efficient RTP materials.In some cases,intermolecular interactions also facilitated RTP emission by regulating the triplet state.On the other hand,heavy atoms(Br,I,etc.),heteroatoms(N,O,S,etc.),or carbonyls were introduced to the molecular skeleton through molecular engineering to enhance intersystem crossing,which is important for populating the triplet exciton.By comprehensively using the aforesaid strategies,great progress has been made for RTP materials.In this mini-review,we summarized recent advances in organic RTP materials based on manipulating intermolecular interactions.Typical host-vip assembly,hydrogen-bond assembly,energy transfer process,and exciplex emission system-based RTP materials were well illustrated.In summary,the current challenges and prospects for development in this field were presented.
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.
