Thermally activated delayed fluorescence(TADF)organic light-emitting diodes(OLEDs)have been demonstrated in applications such as displays and solid-state lightings.However,weak stability and ineffi-cient emission of b...Thermally activated delayed fluorescence(TADF)organic light-emitting diodes(OLEDs)have been demonstrated in applications such as displays and solid-state lightings.However,weak stability and ineffi-cient emission of blue TADF OLEDs are two key bottlenecks limiting the development of solution processable displays and white light sources.This work presents a solution-processed OLED using a blue-emitting TADF small molecule bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone(DMAC-DPS)as an emitter.We comparatively investigated the effects of single host poly(Nvinylcarbazole)(PVK)and a co-host of 60%PVK and 30%2,2′-(1,3-phenylene)-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole](OXD-7)on the device performance(the last 10%is emitter DMAC-DPS).The co-host device shows lower turn-on voltage,similar maximum luminance,and much slower external quantum efficiency(EQE)rolloff.In other words,device stability improved by doping OXD-7 into PVK,and the device impedance simultaneously and significantly reduced from 8.6103 to 4.2103 W at 1000 Hz.Finally,the electroluminescent stability of the co-host device was significantly enhanced by adjusting the annealing temperature.展开更多
To increase the current density of the hole only device, 1, 4, 5, 8, 9, 11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) material has been inserted in the device at the indium tin oxide (ITO)/organic interface. Since ...To increase the current density of the hole only device, 1, 4, 5, 8, 9, 11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) material has been inserted in the device at the indium tin oxide (ITO)/organic interface. Since HATCN molecule can withdraw electrons, it can alter electronic properties of the electrodes and hence inserted between the organic/metal interfaces. This paper deals with the optimization of the thickness of organic-metal layers to enhance the efficiency. Also, efforts have been made to increase the current density and reduce the operating voltage of the device. The material 2, 7-bis [N, N-bis (4- methoxy-phenyl) amino]-9, 9-spirobifluorene (Meo-Spiro-TPD) is used to simulate the hole only device because it is a thermally stable hole transport material. Simulated results shows that better current density values can be achieved compared to fabricated one by optimizing the organic metal layer thickness. The best optimized layer thickness of 22 nm for Alq3, 25 nm for *CBP doped with Ir(ppy)3, 9 nm for Meo-Spiro TPD and 4 nm for HAT-CN which results in current density of 0.12 A/cm2 with a reduction in operating voltage by approximately 2 V.展开更多
基金the National Key Research and Development Program of China(No.2017YFB0404404)the Open Fund of State Key Laboratory of Luminescent Materials and Devices(South China University of Technology),China。
文摘Thermally activated delayed fluorescence(TADF)organic light-emitting diodes(OLEDs)have been demonstrated in applications such as displays and solid-state lightings.However,weak stability and ineffi-cient emission of blue TADF OLEDs are two key bottlenecks limiting the development of solution processable displays and white light sources.This work presents a solution-processed OLED using a blue-emitting TADF small molecule bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone(DMAC-DPS)as an emitter.We comparatively investigated the effects of single host poly(Nvinylcarbazole)(PVK)and a co-host of 60%PVK and 30%2,2′-(1,3-phenylene)-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole](OXD-7)on the device performance(the last 10%is emitter DMAC-DPS).The co-host device shows lower turn-on voltage,similar maximum luminance,and much slower external quantum efficiency(EQE)rolloff.In other words,device stability improved by doping OXD-7 into PVK,and the device impedance simultaneously and significantly reduced from 8.6103 to 4.2103 W at 1000 Hz.Finally,the electroluminescent stability of the co-host device was significantly enhanced by adjusting the annealing temperature.
文摘To increase the current density of the hole only device, 1, 4, 5, 8, 9, 11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) material has been inserted in the device at the indium tin oxide (ITO)/organic interface. Since HATCN molecule can withdraw electrons, it can alter electronic properties of the electrodes and hence inserted between the organic/metal interfaces. This paper deals with the optimization of the thickness of organic-metal layers to enhance the efficiency. Also, efforts have been made to increase the current density and reduce the operating voltage of the device. The material 2, 7-bis [N, N-bis (4- methoxy-phenyl) amino]-9, 9-spirobifluorene (Meo-Spiro-TPD) is used to simulate the hole only device because it is a thermally stable hole transport material. Simulated results shows that better current density values can be achieved compared to fabricated one by optimizing the organic metal layer thickness. The best optimized layer thickness of 22 nm for Alq3, 25 nm for *CBP doped with Ir(ppy)3, 9 nm for Meo-Spiro TPD and 4 nm for HAT-CN which results in current density of 0.12 A/cm2 with a reduction in operating voltage by approximately 2 V.
