具有阶梯势垒的低压有机电致发光器件

Low voltage organic light-emitting devices with step barrier layer

在2-t-butyl-9,10-di-(2-naphthyl)anthracene(TBADN)/tris(8-hydroxyquinoline)aluminum(Alq3)界面及TBADN/4’7-diphyenyl-1,10-phenanthroline(Bphen)界面上插入Gaq薄膜作为阶梯势垒,使有机电致发光器件的电子注入得到改善。由于Gaq(2.9 eV)的LUMO(分子最低空余轨道能级)位于Alq3(3.1 eV)(或Bphen(3.0eV))的LUMO和TBADN的LUMO(2.8 eV)之间,形成了从Alq3(或Bphen)经Gaq到TBADN的势垒阶梯,提高了电子注入,进而提高了器件效率。实验表明:与没有阶梯势垒的器件相比,无论是单一电子器件还是完整器件,在相同电流密度下,具有阶梯势垒的器件的电压都有所下降。在电流密度为20 mA/cm2时,当电子传输层为Alq3时,单一电子器件的电压从7.9 V降到4.9 V,完整器件的电压从7 V降到5.8 V;当电子传输层为Bphen时,单一电子器件的电压从4.2 V降到3.1 V,完整器件的电压从6.2 V降到5.1 V。在电流密度为200mA/cm2,Alq3为电子传输层时,亮度从1 992 cd/m2升到3 281 cd/m2,最高亮度达到3 420 cd/m2,Bphen为电子传输层时,亮度从1745 cd/m2升到2876 cd/m2,最高亮度达到3176 cd/m2。本文运用能级隧穿理论对上述现象进行了解释。

The electron injection transportation in OLEDs were improved by using a Gaq layer between tris（8-hydroxyquinoline）aluminum（Alq3）（or 4＇7-diphyenyl-1,10-phenanthroline（Bphen）） and 2-t-butyl-9,10-di-（2-naphthyl） anthracene（TBADN） as step barrier.Because the lowest unoccupied molecular orbital（LUMO） of Gaq（2.9 eV） lies in between that of Alq3（3.1 eV）（or Bphen（3.0e V）） and TBADN（2.8 eV）,step barrier from Alq3（or BPhen） through Gaq to TBADN can be formed.The experimental results indicate that：The J-V characteristics of both the electron-only and the complete devices show the increase of the current density in devices with step barrier compared with that without step barrier.For electron-only devices,the driving voltage at the current density of 20 mA/cm^2 were reduced from 7.9 V to 4.9 V for devices with Alq3,and from 4.2 V to 3.1 V for devices with Bphen respectively owing to the introduce of step barrier.For the complete devices,after Gag step barrier was introduced.at 20 mA/cm^2,the driving voltage were reduced from 7 V to 5.8 V for devices with Alq3 and from 6.2 V to 5.1 V for devices with Bphen.When step barrier was introduced,the luminance at 200 mA/cm^2 were increased from 1 992 cd/m^2 to 3 281 cd/m^2 for device with Alq3,and from 1 745 cd/m^2 to 2 876 cd/m^2 for devices with BPhen respectively.The phenomena were explained by using tunnel theory