Developing organic multiple-resonance(MR)deep-blue emitters with narrow full widths at half maximum(FWHMs)is crucial for enhancing the color purity of organic light-emitting diodes(OLEDs).However,the exploration of ne...Developing organic multiple-resonance(MR)deep-blue emitters with narrow full widths at half maximum(FWHMs)is crucial for enhancing the color purity of organic light-emitting diodes(OLEDs).However,the exploration of new MR cores remains very limited to date.Furthermore,redshifting the emission color of MR emitters is also a formidable challenge.Pyrazine,characterized by its planar and rigid structure,exhibits a strong electronegativity,which may make it a promising candidate for constructing MR emitters with a red shifted emission compared to indolo[3,2,1-jk]carbazole(ICz)-based MR molecules.Herein,a series of polycyclic aromatic hydrocarbons(PAHs)with MR characteristics are designed and synthesized by integrating a pyrazine core with various electron-donating segments,which exhibit the narrowband deep-blue emission peaks ranging from 423 to 459 nm with FWHMs<50 nm in toluene.It is demonstrated that increasing donor strength and changing meta-to paraoriented nitrogen atom can induce the bathochromic emission.Theoretical investigations reveal that the non-bonding orbital characteristic of pyrazine suppress the undesired stretching vibration and promote resonance effect.The optimized deep-blue OLEDs fabricated with the pyrazine-embedded MR emitters demonstrate a high external quantum efficiency(EQE)of 23.5%,and narrowband emission with an electroluminescence peak at 454 nm.展开更多
Organic light-emitting diodes(OLEDs)based on multiple resonance-thermallyactivated delayedfluorescence(MR-TADF)have the advantages of high excitonutilization and excellent color purity.However,the large conjugated plan...Organic light-emitting diodes(OLEDs)based on multiple resonance-thermallyactivated delayedfluorescence(MR-TADF)have the advantages of high excitonutilization and excellent color purity.However,the large conjugated planarity of gen-eral MR-TADF emitters makes them easily aggregate in the form ofπ–πstacking,resulting in aggregation-caused quenching(ACQ)and the formation of excimers,which reduce exciton utilization efficiency and color purity.To address these issues,large shielding units can be incorporated to prevent interchromophore interactions,whereas the majority of reported molecules are limited to blue-green light emis-sions.This work proposes a strategy of incorporating steric hindrance groups atdifferent sites of the B/N core to suppress interactions between chromophore,con-tributing to blue MR-TADF emitters with high photo-luminance quantum yields(PLQYs≥95%)and narrow full width at half maximum(FWHM),and importantly,great suppression of the ACQ effect.Therefore,blue OLEDs achieve high externalquantum efficiencies up to 34.3%and high color purity with FWHM of about 27 nmand CIE around(0.12,0.15),even at a high doping concentration of 20 wt%.展开更多
Multiple-resonance thermally activated delayed fluorescence(MR-TADF)materials hold significant promise for advancing narrowband emissive organic light-emitting diodes(OLEDs)due to their attractive narrowband emission ...Multiple-resonance thermally activated delayed fluorescence(MR-TADF)materials hold significant promise for advancing narrowband emissive organic light-emitting diodes(OLEDs)due to their attractive narrowband emission characteristics,high emission intensity,and tunable emission colors.However,the planar nature of MRTADF materials leads to serveπ-πstacking,which can result in concentration quenching and spectral broadening,thereby limiting their further application in OLEDs.Currently,to mitigate theπ-πstacking in MR-TADF materials,steric modulation is a reliable design strategy for optimizing the related molecular structures.Depending on the specific shape and scope of steric modulation,it can be categorized into the introduction of bulky groups around the resonance core,“face-to-edge”and“face-to-face”shielding between the resonance core and the steric hindrance moiety.This review systematically summarizes the structural design of MR-TADF molecules based on the different steric modulation strategies and their progress in the doping concentration-independent OLEDs.It also discusses the challenges in this research area and offers an outlook on future developments.We believe that this review will drive the rapid industrialization of narrow-emission OLEDs.展开更多
Helicene-based emitters with unique inherent circularly polarized luminescence(CPL)are promising yet remain a formidable challenge for highly efficient circularly polarized organic light-emitting diodes(CP-OLEDs),ascr...Helicene-based emitters with unique inherent circularly polarized luminescence(CPL)are promising yet remain a formidable challenge for highly efficient circularly polarized organic light-emitting diodes(CP-OLEDs),ascribed to their tough synthesis,low emission efficiency,and easy racemization in the thermal deposition process.Herein,a pair of helicenebased enantiomers,namely(P)-helicene-BN and(M)-helicene-BN,were developed,which merge helical chirality and the B/N/S inserted polycyclic aromatic framework to concurrently feature CPL and narrow thermally activated delayed fluorescence(TADF)characteristics.Benefiting from the excellent thermal/photophysical/chiroptical properties,the narrowband green CP-OLEDs based on enantiomers achieved maximum external quantum efficiencies(EQE_(max))of up to 31.5%,and dissymmetry factor(|g_(EL)|)of 2.2×10^(−3).This work reveals the great potential of helicene-based emitters in CP-OLEDs.展开更多
Organic light-emitting diodes utilizing thermally activated delayed fluorescence sensitizers and multiple-resonance(MR)dopants may simultaneously offer high efficiencies and narrow-band emissions,but these devices sti...Organic light-emitting diodes utilizing thermally activated delayed fluorescence sensitizers and multiple-resonance(MR)dopants may simultaneously offer high efficiencies and narrow-band emissions,but these devices still face intractable challenges with a lack of design rules for high-performance sensitizers.Here,sensitizers with ortho-arranged donor–acceptors on a(trifluoromethyl)benzene linker have been proposed,which not only facilitate relatively small molecular dipole moments but also combine through-bond and through-space charge transfers for fast reverse intersystem crossing(RISC).展开更多
The inception and harnessing of excitons are paramount for the electroluminescence performance of organic light-emitting devices(OLEDs).Through-space charge transfer(TSCT)via intramolecular interaction has proved to b...The inception and harnessing of excitons are paramount for the electroluminescence performance of organic light-emitting devices(OLEDs).Through-space charge transfer(TSCT)via intramolecular interaction has proved to be one of the most potent techniques employed to achieve 100% internal quantum efficiency.However,molecular strategies utilized to comprehensively enhance the electroluminescent performance of TSCT emitters regarding improving the photoluminescence quantum yield(PLQY)and elevating the light out-coupling efficiency remain arduous.To surmount this challenge,we deliberately designed and synthesized a proof-of-concept TSCT emitter called CzO-TRZ by incorporating an extra carbazole donor into spiroheterocyclic architecture.The introduction of rigid spiral fragments can immensely boost the horizontal orientation dipole ratio and establish an extra through-bond charge transfer(TBCT)radiative decay channel.As a result,a very high PLQY of 98.7%,fast kRISCof 2.2×10^(5)s^(-1)and high k_(r)^(s) of 2.2×10^(7)s^(-1),and an ultrahigh horizontal dipolar ratio of 90%were concurrently achieved for Cz O-TRZ blended films.Furthermore,corresponding thermally activated delayed fluorescence(TADF)-and TADF-sensitized fluorescence(TSF)-OLEDs based on CzO-TRZ demonstrated external quantum efficiencies(EQEs)of 33.4% and 30.3%,respectively,highlighting its versatile applications as both an emitter and sensitized host.展开更多
基金financial support from the National Natural Science Foundation of China (52130308)Shenzhen Science and Technology Program (JCYJ20220818095816036,ZDSYS20210623091813040)。
文摘Developing organic multiple-resonance(MR)deep-blue emitters with narrow full widths at half maximum(FWHMs)is crucial for enhancing the color purity of organic light-emitting diodes(OLEDs).However,the exploration of new MR cores remains very limited to date.Furthermore,redshifting the emission color of MR emitters is also a formidable challenge.Pyrazine,characterized by its planar and rigid structure,exhibits a strong electronegativity,which may make it a promising candidate for constructing MR emitters with a red shifted emission compared to indolo[3,2,1-jk]carbazole(ICz)-based MR molecules.Herein,a series of polycyclic aromatic hydrocarbons(PAHs)with MR characteristics are designed and synthesized by integrating a pyrazine core with various electron-donating segments,which exhibit the narrowband deep-blue emission peaks ranging from 423 to 459 nm with FWHMs<50 nm in toluene.It is demonstrated that increasing donor strength and changing meta-to paraoriented nitrogen atom can induce the bathochromic emission.Theoretical investigations reveal that the non-bonding orbital characteristic of pyrazine suppress the undesired stretching vibration and promote resonance effect.The optimized deep-blue OLEDs fabricated with the pyrazine-embedded MR emitters demonstrate a high external quantum efficiency(EQE)of 23.5%,and narrowband emission with an electroluminescence peak at 454 nm.
基金National Natural Science Foundation of China,Grant/Award Numbers:51733010,52073316Basic and Applied Basic Research Foundation of Guangdong Province,Grant/Award Numbers:2022B1515020052,2021A1515110119。
文摘Organic light-emitting diodes(OLEDs)based on multiple resonance-thermallyactivated delayedfluorescence(MR-TADF)have the advantages of high excitonutilization and excellent color purity.However,the large conjugated planarity of gen-eral MR-TADF emitters makes them easily aggregate in the form ofπ–πstacking,resulting in aggregation-caused quenching(ACQ)and the formation of excimers,which reduce exciton utilization efficiency and color purity.To address these issues,large shielding units can be incorporated to prevent interchromophore interactions,whereas the majority of reported molecules are limited to blue-green light emis-sions.This work proposes a strategy of incorporating steric hindrance groups atdifferent sites of the B/N core to suppress interactions between chromophore,con-tributing to blue MR-TADF emitters with high photo-luminance quantum yields(PLQYs≥95%)and narrow full width at half maximum(FWHM),and importantly,great suppression of the ACQ effect.Therefore,blue OLEDs achieve high externalquantum efficiencies up to 34.3%and high color purity with FWHM of about 27 nmand CIE around(0.12,0.15),even at a high doping concentration of 20 wt%.
基金supported by the National Natural Science Foundation of China(No.22005158)Natural Science Foundation of Nantong(No.JC2023090).
文摘Multiple-resonance thermally activated delayed fluorescence(MR-TADF)materials hold significant promise for advancing narrowband emissive organic light-emitting diodes(OLEDs)due to their attractive narrowband emission characteristics,high emission intensity,and tunable emission colors.However,the planar nature of MRTADF materials leads to serveπ-πstacking,which can result in concentration quenching and spectral broadening,thereby limiting their further application in OLEDs.Currently,to mitigate theπ-πstacking in MR-TADF materials,steric modulation is a reliable design strategy for optimizing the related molecular structures.Depending on the specific shape and scope of steric modulation,it can be categorized into the introduction of bulky groups around the resonance core,“face-to-edge”and“face-to-face”shielding between the resonance core and the steric hindrance moiety.This review systematically summarizes the structural design of MR-TADF molecules based on the different steric modulation strategies and their progress in the doping concentration-independent OLEDs.It also discusses the challenges in this research area and offers an outlook on future developments.We believe that this review will drive the rapid industrialization of narrow-emission OLEDs.
基金This work was supported by the National Natural Science Foundation of China(grant nos.52130308,51903160,and 52022071)Shenzhen Science and Technology Program(grant no.KQTD20170330110107046)the Shenzhen Technology and Innovation Commission(grant no.JCYJ20180507182244027).
文摘Helicene-based emitters with unique inherent circularly polarized luminescence(CPL)are promising yet remain a formidable challenge for highly efficient circularly polarized organic light-emitting diodes(CP-OLEDs),ascribed to their tough synthesis,low emission efficiency,and easy racemization in the thermal deposition process.Herein,a pair of helicenebased enantiomers,namely(P)-helicene-BN and(M)-helicene-BN,were developed,which merge helical chirality and the B/N/S inserted polycyclic aromatic framework to concurrently feature CPL and narrow thermally activated delayed fluorescence(TADF)characteristics.Benefiting from the excellent thermal/photophysical/chiroptical properties,the narrowband green CP-OLEDs based on enantiomers achieved maximum external quantum efficiencies(EQE_(max))of up to 31.5%,and dissymmetry factor(|g_(EL)|)of 2.2×10^(−3).This work reveals the great potential of helicene-based emitters in CP-OLEDs.
基金supported by the National Key Basic Research and Development Program of China(grant no.2017YFA0204501)the National Natural Science Foundation of China(grant nos.51525304,51903137,U1601651,and 61890942)+1 种基金Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-005)the Guangdong Major Project of Basic and Applied Basic Research(grant no.2019B030302009).
文摘Organic light-emitting diodes utilizing thermally activated delayed fluorescence sensitizers and multiple-resonance(MR)dopants may simultaneously offer high efficiencies and narrow-band emissions,but these devices still face intractable challenges with a lack of design rules for high-performance sensitizers.Here,sensitizers with ortho-arranged donor–acceptors on a(trifluoromethyl)benzene linker have been proposed,which not only facilitate relatively small molecular dipole moments but also combine through-bond and through-space charge transfers for fast reverse intersystem crossing(RISC).
基金supported by the National Natural Science Foundation of China(U21A20331,51773212,81903743,52003088)the Distinguished Young Scholars(21925506)the Ningbo Key Scientific and Technological Project(2022Z124,2022Z119)。
文摘The inception and harnessing of excitons are paramount for the electroluminescence performance of organic light-emitting devices(OLEDs).Through-space charge transfer(TSCT)via intramolecular interaction has proved to be one of the most potent techniques employed to achieve 100% internal quantum efficiency.However,molecular strategies utilized to comprehensively enhance the electroluminescent performance of TSCT emitters regarding improving the photoluminescence quantum yield(PLQY)and elevating the light out-coupling efficiency remain arduous.To surmount this challenge,we deliberately designed and synthesized a proof-of-concept TSCT emitter called CzO-TRZ by incorporating an extra carbazole donor into spiroheterocyclic architecture.The introduction of rigid spiral fragments can immensely boost the horizontal orientation dipole ratio and establish an extra through-bond charge transfer(TBCT)radiative decay channel.As a result,a very high PLQY of 98.7%,fast kRISCof 2.2×10^(5)s^(-1)and high k_(r)^(s) of 2.2×10^(7)s^(-1),and an ultrahigh horizontal dipolar ratio of 90%were concurrently achieved for Cz O-TRZ blended films.Furthermore,corresponding thermally activated delayed fluorescence(TADF)-and TADF-sensitized fluorescence(TSF)-OLEDs based on CzO-TRZ demonstrated external quantum efficiencies(EQEs)of 33.4% and 30.3%,respectively,highlighting its versatile applications as both an emitter and sensitized host.
