Metal TADF(thermally activated delayed fluorescence)emitters,here understood as those containing a d-block metal,are an important and ever-growing group of luminophores.Although they often seem to belong more in the t...Metal TADF(thermally activated delayed fluorescence)emitters,here understood as those containing a d-block metal,are an important and ever-growing group of luminophores.Although they often seem to belong more in the transition metal complex world,they are rightful contenders of not only phosphorescent transition metal compounds,but also conventional,metal-free TADF emitters.Their unique properties include extremely short TADF lifetimes,often in the range 0.1-10μs,fast intersystem crossing(ISC)and reverse ISC(RISC),minimal prompt fluorescence or lack thereof,small Stokes shifts,and temperature-dependent behaviour,including dual TADF/phosphorescence emission-but not every metal TADF emitter displays all of them at once!In this review,we discuss the general photophysical properties of metal TADF emitters and the relevant photophysical approaches applicable to studies of them.We make a brief overview of the most recent examples of computational works on metal TADF luminophores that shed some light on the up-conversion mechanism.Finally,we review some recent examples of Cu(Ⅰ),Ag(Ⅰ),Au(Ⅰ)/Au(Ⅲ)as well as Zn(Ⅱ)TADF emitters,and discuss possibly all relevant works on Pd(Ⅱ),Pt(Ⅱ),Ir(Ⅲ),and Zr(Ⅳ)TADF complexes.We identify that metal TADF complexes form two principal groups:(Ⅰ)those analogous to donor-acceptor or charge-transfer TADF emitters and(Ⅱ)those analogous to multiresonance TADF emitters.展开更多
Dinuclear platinum(Ⅱ)complexes of a new,ditopic,bis-tridentate NCN-NCN-coordinating ligand,appended with four mesityl groups,are reported.The high radiative rate constants and correspondingly efficient luminescence o...Dinuclear platinum(Ⅱ)complexes of a new,ditopic,bis-tridentate NCN-NCN-coordinating ligand,appended with four mesityl groups,are reported.The high radiative rate constants and correspondingly efficient luminescence of the complexes involves thermally activated delayed fluorescence(TADF),thanks to a near-zero energy gap between the S_(1) and T_(1) states.The mesityl groups also serve to hinder the aggregation that was detrimental to electroluminescence efficiency in previous studies,allowing a~4-fold increase in OLED efficiency to be achieved(i.e.from 2.3% previously to 10% in this work).Oxidation of one of the Pt(Ⅱ)complexes led to a dinuclear Pt(Ⅳ)complex of unprecedented structure.展开更多
In this work we report the second ever example of a fully experimentally confirmed thermally activated delayed fluorescence(TADF)in a dinuclear Ir(Ⅲ)complex.The said complex displays a singlet-triplet gap ΔE_(ST)=28...In this work we report the second ever example of a fully experimentally confirmed thermally activated delayed fluorescence(TADF)in a dinuclear Ir(Ⅲ)complex.The said complex displays a singlet-triplet gap ΔE_(ST)=28±5 meV,in agreement with the computational prediction of 31.1 meV-a value smaller than the previous TADF Ir(Ⅲ)complex.We also demonstrate a proof-of-concept,solution-processed OLED featuring this complex as the luminescent dopant in the emissive layer,achieving external quantum efficiency of up to~10%and maximum luminance of 18000 cd m^(−2)-values significantly exceeding those reported earlier for Ir(Ⅲ)TADF.These findings are preceded by a detailed consideration of spectral signs of TADF in the already known Ir(Ⅲ)complexes.The spectral overlap of photoluminescence(PL)with strong(i.e.,spin-allowed)absorption bands is unusual for phosphorescent metal complexes,because the PL originates from the triplet state,which is normally significantly lower in energy than the lowest-lying singlet.In this study,we have scrutinized literature data on iridium(Ⅲ)complexes that likewise show significant overlap between absorption and PL,and we conclude that a small singlet-triplet energy gap ΔE_(ST) in these complexes results in a TADF contribution to their emission.Such a mechanism has hitherto been overlooked in the large body of iridium(Ⅲ)chemistry.We use computations to clarify the nature of the excited states in these complexes,demonstrating that the distinctive S_(1) and T_(1) character of states can be identified as well as confirming that ΔE_(ST) is small enough for TADF to occur at room temperature.展开更多
基金National Science Centre,Poland for funding,grant no.2022/45/B/ST4/02689Silesian University of Technology for Rector’s pro-quality grant no.04/040/RGJ26/0329.
文摘Metal TADF(thermally activated delayed fluorescence)emitters,here understood as those containing a d-block metal,are an important and ever-growing group of luminophores.Although they often seem to belong more in the transition metal complex world,they are rightful contenders of not only phosphorescent transition metal compounds,but also conventional,metal-free TADF emitters.Their unique properties include extremely short TADF lifetimes,often in the range 0.1-10μs,fast intersystem crossing(ISC)and reverse ISC(RISC),minimal prompt fluorescence or lack thereof,small Stokes shifts,and temperature-dependent behaviour,including dual TADF/phosphorescence emission-but not every metal TADF emitter displays all of them at once!In this review,we discuss the general photophysical properties of metal TADF emitters and the relevant photophysical approaches applicable to studies of them.We make a brief overview of the most recent examples of computational works on metal TADF luminophores that shed some light on the up-conversion mechanism.Finally,we review some recent examples of Cu(Ⅰ),Ag(Ⅰ),Au(Ⅰ)/Au(Ⅲ)as well as Zn(Ⅱ)TADF emitters,and discuss possibly all relevant works on Pd(Ⅱ),Pt(Ⅱ),Ir(Ⅲ),and Zr(Ⅳ)TADF complexes.We identify that metal TADF complexes form two principal groups:(Ⅰ)those analogous to donor-acceptor or charge-transfer TADF emitters and(Ⅱ)those analogous to multiresonance TADF emitters.
基金the National Science Centre,Poland for funding under grant no.2022/47/D/ST4/01496the Rector’s pro-quality grant,Silesian University of Technology,Poland,grant no:04/040/RGJ24/0279+1 种基金funding from EPRSC(grant ref.EP/S012788/1)Durham University Chemistry for partial support of a PhD studentship.
文摘Dinuclear platinum(Ⅱ)complexes of a new,ditopic,bis-tridentate NCN-NCN-coordinating ligand,appended with four mesityl groups,are reported.The high radiative rate constants and correspondingly efficient luminescence of the complexes involves thermally activated delayed fluorescence(TADF),thanks to a near-zero energy gap between the S_(1) and T_(1) states.The mesityl groups also serve to hinder the aggregation that was detrimental to electroluminescence efficiency in previous studies,allowing a~4-fold increase in OLED efficiency to be achieved(i.e.from 2.3% previously to 10% in this work).Oxidation of one of the Pt(Ⅱ)complexes led to a dinuclear Pt(Ⅳ)complex of unprecedented structure.
基金the National Science Centre,Poland for funding,grant no.2022/45/B/ST4/02689.
文摘In this work we report the second ever example of a fully experimentally confirmed thermally activated delayed fluorescence(TADF)in a dinuclear Ir(Ⅲ)complex.The said complex displays a singlet-triplet gap ΔE_(ST)=28±5 meV,in agreement with the computational prediction of 31.1 meV-a value smaller than the previous TADF Ir(Ⅲ)complex.We also demonstrate a proof-of-concept,solution-processed OLED featuring this complex as the luminescent dopant in the emissive layer,achieving external quantum efficiency of up to~10%and maximum luminance of 18000 cd m^(−2)-values significantly exceeding those reported earlier for Ir(Ⅲ)TADF.These findings are preceded by a detailed consideration of spectral signs of TADF in the already known Ir(Ⅲ)complexes.The spectral overlap of photoluminescence(PL)with strong(i.e.,spin-allowed)absorption bands is unusual for phosphorescent metal complexes,because the PL originates from the triplet state,which is normally significantly lower in energy than the lowest-lying singlet.In this study,we have scrutinized literature data on iridium(Ⅲ)complexes that likewise show significant overlap between absorption and PL,and we conclude that a small singlet-triplet energy gap ΔE_(ST) in these complexes results in a TADF contribution to their emission.Such a mechanism has hitherto been overlooked in the large body of iridium(Ⅲ)chemistry.We use computations to clarify the nature of the excited states in these complexes,demonstrating that the distinctive S_(1) and T_(1) character of states can be identified as well as confirming that ΔE_(ST) is small enough for TADF to occur at room temperature.
