To attain high efficiencies in hybrid white organic light-emitting diodes(WOLEDs),mutual quenching of the fluorophors and phosphors should be minimized.Efforts have been devoted to reducing the triplet quenching of ph...To attain high efficiencies in hybrid white organic light-emitting diodes(WOLEDs),mutual quenching of the fluorophors and phosphors should be minimized.Efforts have been devoted to reducing the triplet quenching of phosphors;however,the quenching of fluorophors by the external heavy-atom effect(EHA)introduced by the phosphors is often ignored.Here,we observed that conventional fluorophors and fluorophors with thermally activated delayed fluorescence(TADF)behave differently in the presence of EHA perturbers.The efficiencies of the conventional fluorophors suffer greatly from the EHA,whereas the TADF fluorophors exhibit negligible changes,which makes TADF materials ideal fluorophors for hybrid devices.WOLEDs using a blue TADF fluorophor and an orange phosphor achieve a maximum forward viewing external quantum efficiency of 19.6%and a maximum forward viewing power efficiency of 50.2 lm W^(-1),among the best values for hybrid WOLEDs.This report is the first time that the EHA effect has been considered in hybrid WOLEDs and that a general strategy toward highly efficient hybrid WOLEDs with simple structures is proposed.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
High cost of phosphors and significant efficiency roll-off at high brightness are the two main factors that limit the wide application of phosphorescent organic light-emitting diodes (PHOLEDs). Efforts have been paid ...High cost of phosphors and significant efficiency roll-off at high brightness are the two main factors that limit the wide application of phosphorescent organic light-emitting diodes (PHOLEDs). Efforts have been paid to find ways to reduce the phosphors’ concentration and efficiency roll-off of PHOLEDs. In this work, we reported red emission PHOLEDs with low dopant concentration and low efficiency roll-off based on a novel host material 2,4-biscyanophenyl-6-(12-phenylindole[2,3-a]carbazole-11-yl)-1,3,5-triazine (BCPICT), with thermally activated delayed fluorescent(TADF) properties. The device with 1.0% dopant concentration displayed a maximum external quantum efficiency of 10.7%.When the dopant concentration was increased to 2.0%, the device displayed a maximum external quantum efficiency of 10.5% and a low efficiency roll-off of 5.7% at 1000 cd/m2.展开更多
Promoting electron mobility is the key to designing high performance electron transport materials(ETMs). Formation of intermolecular interaction can be helpful to enhance their electron mobilities as a result of more ...Promoting electron mobility is the key to designing high performance electron transport materials(ETMs). Formation of intermolecular interaction can be helpful to enhance their electron mobilities as a result of more ordered molecular stacking.Here, to reveal the inherent influence of intermolecular π-π stacking on the electron mobilities, we designed two ETMs, namely,2,4-diphenyl-6-[3-(2-triphenylenyl)phenyl]-1,3,5-triazine(TPTRZ) and 2,4-diphenyl-6-[4′-(2-triphenylenyl)[1,1′-biphenyl]-3-yl]-1,3,5-triazine(TPPTRZ). Thermal, photophysical and electrochemical measurement results indicate they are good ETM candidates. Additionally, TPTRZ and TPPTRZ exhibit high electron mobilities of 3.60×10^(-5) and 3.58×10^(-5) cm^2V-1 s^(-1), respectively, at an electric field of 7×10~5 V cm^(-1). By taking X-ray single crystal structure, theoretical calculation and time of flight(TOF) results into consideration, it is revealed that strong intermolecular π-π stacking induced by planar triphenylene and triphenyltriazine units renders TPTRZ and TPPTRZ small energetic and positional disorder parameters, and results in their high electron mobilities thereby. By further enhancing intermolecular π-π stacking, ETMs with even higher electron mobilities can thus be anticipated.展开更多
基金We would like to thank the National Natural Science Foundation of China(Grant Nos.51173096,21161160447 and 61177023)for financial support.
文摘To attain high efficiencies in hybrid white organic light-emitting diodes(WOLEDs),mutual quenching of the fluorophors and phosphors should be minimized.Efforts have been devoted to reducing the triplet quenching of phosphors;however,the quenching of fluorophors by the external heavy-atom effect(EHA)introduced by the phosphors is often ignored.Here,we observed that conventional fluorophors and fluorophors with thermally activated delayed fluorescence(TADF)behave differently in the presence of EHA perturbers.The efficiencies of the conventional fluorophors suffer greatly from the EHA,whereas the TADF fluorophors exhibit negligible changes,which makes TADF materials ideal fluorophors for hybrid devices.WOLEDs using a blue TADF fluorophor and an orange phosphor achieve a maximum forward viewing external quantum efficiency of 19.6%and a maximum forward viewing power efficiency of 50.2 lm W^(-1),among the best values for hybrid WOLEDs.This report is the first time that the EHA effect has been considered in hybrid WOLEDs and that a general strategy toward highly efficient hybrid WOLEDs with simple structures is proposed.
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 (51525304)the National Key Basic Research and Development Program of China (2015CB655002)
文摘High cost of phosphors and significant efficiency roll-off at high brightness are the two main factors that limit the wide application of phosphorescent organic light-emitting diodes (PHOLEDs). Efforts have been paid to find ways to reduce the phosphors’ concentration and efficiency roll-off of PHOLEDs. In this work, we reported red emission PHOLEDs with low dopant concentration and low efficiency roll-off based on a novel host material 2,4-biscyanophenyl-6-(12-phenylindole[2,3-a]carbazole-11-yl)-1,3,5-triazine (BCPICT), with thermally activated delayed fluorescent(TADF) properties. The device with 1.0% dopant concentration displayed a maximum external quantum efficiency of 10.7%.When the dopant concentration was increased to 2.0%, the device displayed a maximum external quantum efficiency of 10.5% and a low efficiency roll-off of 5.7% at 1000 cd/m2.
基金supported by the National Key Research and Development Program of China (2017YFA0204501)the National Natural Science Foundation of China (51525304, U1601651)+1 种基金the National Basic Research Program of China (2015CB655002)the Tsinghua University Initiative Scientific Research Program (20161080039, 20161080040)
文摘Promoting electron mobility is the key to designing high performance electron transport materials(ETMs). Formation of intermolecular interaction can be helpful to enhance their electron mobilities as a result of more ordered molecular stacking.Here, to reveal the inherent influence of intermolecular π-π stacking on the electron mobilities, we designed two ETMs, namely,2,4-diphenyl-6-[3-(2-triphenylenyl)phenyl]-1,3,5-triazine(TPTRZ) and 2,4-diphenyl-6-[4′-(2-triphenylenyl)[1,1′-biphenyl]-3-yl]-1,3,5-triazine(TPPTRZ). Thermal, photophysical and electrochemical measurement results indicate they are good ETM candidates. Additionally, TPTRZ and TPPTRZ exhibit high electron mobilities of 3.60×10^(-5) and 3.58×10^(-5) cm^2V-1 s^(-1), respectively, at an electric field of 7×10~5 V cm^(-1). By taking X-ray single crystal structure, theoretical calculation and time of flight(TOF) results into consideration, it is revealed that strong intermolecular π-π stacking induced by planar triphenylene and triphenyltriazine units renders TPTRZ and TPPTRZ small energetic and positional disorder parameters, and results in their high electron mobilities thereby. By further enhancing intermolecular π-π stacking, ETMs with even higher electron mobilities can thus be anticipated.