间隔层对红绿磷光有机电致发光器件发光性能的影响

制备了结构为ITO/MoO₃(40 nm)/NPB(40 nm)/TCTA(10 nm)/CBP∶GIr1(14%)∶R-4B(2%)(20 nm) /间隔层(3 nm)/ CBP∶GIr1(14%)∶R-4B(2%)(10 nm)/BCP(10 nm)/Alq₃(40 nm)/LiF(1 nm)/Al(100 nm) 的有机电致发光器件，间隔层分别为CBP，TCTA，TPBI和BCP，GIr1和R-4B分别为绿红磷光材料。通过加入不同间隔层来调控载流子和激子在发光层内的分布并研究了其对器件发光性能的影响。研究表明TCTA，TPBI和BCP分别作为间隔层的器件较CBP为间隔层的参考器件，电压为6 V时，电流效率分别高出59%，79%和93%，以BCP为间隔层的器件效率最高达到22.58 cd·A-1;TPBI和BCP为间隔层相对于以TCTA为间隔层的器件，在较高的电流密度下，效率滚降更小。分析原因TCTA间隔层较高的LUMO能级和三线态能量将电子和激子限制在较窄的复合区域，提高了载流子相遇形成激子的概率，在较高电流密度下猝灭也更严重;TPBI和BCP由于具有较高的HOMO能级和电子传输能力，拓宽了激子的复合区域。间隔层引起电子或空穴的累积，形成较高的空间电场，有利于发光层相应载流子的注入与传输。由于发光层掺杂方式为红绿共掺，器件均获得了较好的色坐标稳定性。

Effect of Spacer on Red and Green Phosphorescent Organic Light-Emitting Devices

We have investigated the performances of organic light-emitting diodes (OLED) with different spacer, the structure was fabricated as ITO/MoO₃(40 nm)/NPB(40 nm)/TCTA(10 nm)/CBP∶GIr114%∶R-4B2%(30 nm)/spacer (3 nm)/ CBP∶GIr114%∶R-4B2%(30 nm)/BCP(10 nm)/Alq₃(40 nm)/LiF(1 nm)/Al(100 nm), the spacers were CBP，TCTA，TPBI and BCP separately, GIr1 and R-4B were green and red phosphorescent dye respectively. The results showed that compared to the reference device utilized CBP as the spacer layer, TCTA，TPBI and BCP had higher current efficiency in excess of 59%，79% and 93%, the maximum current efficiency of 16.91 cd·A-1 was achieved with BCP as the spacer at voltage of 5 V, TPBI and BCP as the spacer layer obtained the higher current density and lower efficiency roll-off. We attributed to these results to the follow reasons, the first was that carriers and excitons were limited to a narrow recombination region because of TCTA with higher LUMO energy level and triplet energy, which improved the probability of carriers recombination, in addition, more serious quenching at higher current density. The second reason was that TPBI and BCP had the higher HOMO energy level and electron mobility, which broadened excitons recombination zone. In addition, the spacer layer caused the accumulation of electrons or holes and the formation of high space electric field, leading to carrier injection and transport more effectively. In particular, we obtained a better stability of phosphorescent organic light-emitting diodes since the way for the red and green co-doped with host material.