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
Thermally activated delayed fluorescence(TADF) sensitized fluorescent organic light-emitting diodes(TSF-OLEDs) have shown great potential for the realization of high efficiency with low efficiency rolloff and good col...Thermally activated delayed fluorescence(TADF) sensitized fluorescent organic light-emitting diodes(TSF-OLEDs) have shown great potential for the realization of high efficiency with low efficiency rolloff and good color purity. However, the superior examples of TSF-OLEDs are still limited up to now.Herein, a trade-off strategy is presented for designing efficient TADF materials and achieving highperformance TSF-OLEDs via the construction of a new type of triazolotriazine(TAZTRZ) acceptor. The enhanced electron-withdrawing ability of TAZTRZ acceptor, fused by triazine(TRZ) and triazole(TAZ)together, enables TADF luminogens with small singlet-triplet energy gap(ΔE_(ST)) values. Meanwhile, the increased planarity from the TRZ-phenyl linkage(6:6 system) to the TAZ-phenyl linkage(5:6 system)can compensate the decrease of oscillator strength(f) while lowing ΔE_(ST), thus achieving a trade-off between small ΔE_(ST) and high f. As a result, the related TSF-OLED achieved an extremely low turn-on voltage of 2.1 V, an outstanding maximum external quantum efficiency(EQEmax) of 23.7% with small efficiency roll-off(EQE1000 of 23.2%;EQE5000 of 20.6%) and an impressively high maximum power efficiency of 82.1 lm W^(-1), which represents the state-of-the-art performance for yellow TSF-OLEDs.展开更多
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This work was supported by the National Natural Science Foundation of China(21432005)the Fundamental Research Funds for the Central Universities and the Comprehensive Training Platform Specialized Laboratory,College of Chemistry,Sichuan University。
文摘Thermally activated delayed fluorescence(TADF) sensitized fluorescent organic light-emitting diodes(TSF-OLEDs) have shown great potential for the realization of high efficiency with low efficiency rolloff and good color purity. However, the superior examples of TSF-OLEDs are still limited up to now.Herein, a trade-off strategy is presented for designing efficient TADF materials and achieving highperformance TSF-OLEDs via the construction of a new type of triazolotriazine(TAZTRZ) acceptor. The enhanced electron-withdrawing ability of TAZTRZ acceptor, fused by triazine(TRZ) and triazole(TAZ)together, enables TADF luminogens with small singlet-triplet energy gap(ΔE_(ST)) values. Meanwhile, the increased planarity from the TRZ-phenyl linkage(6:6 system) to the TAZ-phenyl linkage(5:6 system)can compensate the decrease of oscillator strength(f) while lowing ΔE_(ST), thus achieving a trade-off between small ΔE_(ST) and high f. As a result, the related TSF-OLED achieved an extremely low turn-on voltage of 2.1 V, an outstanding maximum external quantum efficiency(EQEmax) of 23.7% with small efficiency roll-off(EQE1000 of 23.2%;EQE5000 of 20.6%) and an impressively high maximum power efficiency of 82.1 lm W^(-1), which represents the state-of-the-art performance for yellow TSF-OLEDs.
