Highly efficient non-doped tandem phosphorescent organic light-emitting devices (PhOLEDs) have been demonstrated by employing LiF/AL/1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) as a charge generation unit (CGU) and ultrathin phosphorescent dyes as emitting layers (EMLs). It was found that the performance of the tandem PhOLEDs was significantly dependent on the Al thickness in CGU. Analyses regarding the current density-voltage characteristics of the CGU only devices indicate that the charge carriers are generated at the HAT-CN/NPB interface, and Al/LiF layers work as assistant electron injection layers to facilitate electron extraction from CGU and injection into the adjacent electron transport layer. From the capacitance-voltage and optical transparency characteristics of CGU with different thicknesses of Al interlayer, the thick Al layer is beneficial to charge separation, while it weakens the light output of the tandem device. Under the optimal Al thickness of 5 nm, more than twofold enhancement of current efficiency is achieved for the non-doped tandem blue device. Furthermore, the non-doped tandem white PhOLED was also developed showing a maximum current efficiency of 94.9 cd/A and maximum external quantum efficiency of 31.6%.

通过使用LiF / AL / 1,4,5,8,9,11-六氮杂三苯撑六碳腈（HAT-CN）作为电荷产生单元（CGU），已经证明了高效的非掺杂串联磷光有机发光器件（PhOLED） ）和超薄磷光染料作为发光层（EML）。发现串联PhOLED的性能显着取决于CGU中的Al厚度。有关仅CGU器件的电流密度-电压特性的分析表明，电荷载流子在HAT-CN / NPB界面生成，Al / LiF层用作辅助电子注入层，有助于电子从CGU提取并注入到CGU中。相邻的电子传输层。从不同厚度的Al中间层的CGU的电容电压和光学透明性来看，厚的铝层有利于电荷分离，同时会削弱串联装置的光输出。在5 nm的最佳Al厚度下，非掺杂串联蓝光器件的电流效率提高了两倍以上。此外，还开发了非掺杂的串联白色PhOLED，其最大电流效率为94.9 cd / A，最大外部量子效率为31.6％。