利用LiF空穴阻挡/激子限制层提高有机电致发光器件效率

Improved Efficiency in Organic Light-Emitting Devices With LiF Hole Blocking and Exciton Confining Layers

将厚度为0.5 nm的LiF薄层引入到双层有机电致发光器件（OLEDs）的Alq3发光/电子传输层中作为空穴阻挡/激子限制层,研究其位置对器件光电性能的影响。发现LiF薄层在不同位置均明显提高器件的发光效率,当LiF薄膜距离TPD/Alq3界面20~40 nm时,OLEDs的最大发光效率约为4.5 cd/A,是对比器件（没有LiF薄层）的1.8倍。OLEDs的电流密度随着减小LiF薄层与阴极的距离而增大。研究表明,这是因为LiF薄层可有效阻挡进入复合发光区域未复合的过剩空穴并导致其积累,空穴积累可提高电子传输区域中的电场,提高其中电子的传输和从阴极的注入,从而提高复合发光区域中的载流子平衡及其复合几率;LiF薄层可将激子限制在复合发光区域,减少激子被阴极淬灭的几率。

Here the performance dependence of the organic light-emitting devices（OLEDs） on the location of a 0.5 nm LiF interlayer had been investigated,of which the thin LiF layer was used as a hole blocking and exciton confining layer.It was found that all the OLEDs exhibited improved efficiency when the LiF interlayer was used.When the LiF interlayer located 20~40 nm distance to the interface of TPD/Alq3,OLEDs showed peak electroluminescence efficiencies of around 4.5 cd/A,which is around 1.8 times of that in control device without LiF layer.Meanwhile,the current density of the devices increased when reducing the distance between LiF interlayer and cathode interface.The LiF interlayer was used to block the unrecombined holes at the interface between the recombination region and LiF interlayer,so that the electric field inside electron transport region increased,leading to a better electron transport and injection,improved charge balance and recombination probability in the recombination region.LiF interlayer may also confine the excitons in the recombination region and suppress the exciton quenching by the metal cathode.