Wang Hui, Ryu Jeong-Tak, Kwon Younghwan
College of Information and Communication Engineering, Daegu University, Gyeongsan, Gyeongbuk 712-714, Korea.
J Nanosci Nanotechnol. 2012 May;12(5):4330-4. doi: 10.1166/jnn.2012.5897.
This study examined the influence of the charge injection barriers on the performance of organic light emitting diodes (OLEDs) using polymers with a stepwise tuned ionization potential (I(p) approximately -5.01 - -5.29 eV) between the indium tin oxide (ITO) (phi approximately -4.8 eV) anode and tris(8-hydroxyquinolinato) aluminium (Alq3) (I(p) approximately -5.7 eV) layer. The energy levels of the polymers were tuned by structural modification. Double layer devices were fabricated with a configuration of ITO/polymer/Alq3/LiF/Al, where the polymers, Alq3, and LiF/Al were used as the hole injection/transport layer, emissive electron transport layer, and electron injection/cathode, respectively. Using the current density-voltage (J-V), luminescence-voltage (L-V) and efficiencies in these double layer devices, the device performance was evaluated in terms of the energy level alignments at the interfaces, such as the hole injection barriers (phi(h)(iTO/polymer) and phi(h)(polymer/Alq3)) from ITO through the polymers into the Alq3 layer, and the electron injection barrier (phi(e)(polymer/Alq3) or electron/exciton blocking barrier) at the polymer/Alq3 interface.
本研究考察了电荷注入势垒对有机发光二极管（OLED）性能的影响，该OLED使用了在铟锡氧化物（ITO）（功函数约为-4.8 eV）阳极与三（8-羟基喹啉）铝（Alq3）（电离势约为-5.7 eV）层之间具有逐步调整电离势（I(p)约为-5.01 - -5.29 eV）的聚合物。通过结构修饰来调整聚合物的能级。制备了具有ITO/聚合物/Alq3/LiF/Al结构的双层器件，其中聚合物、Alq3和LiF/Al分别用作空穴注入/传输层、发光电子传输层和电子注入/阴极。利用这些双层器件中的电流密度-电压（J-V）、发光-电压（L-V）和效率，根据界面处的能级排列来评估器件性能，例如从ITO通过聚合物进入Alq3层的空穴注入势垒（φ(h)(ITO/聚合物)和φ(h)(聚合物/Alq3)），以及聚合物/Alq3界面处的电子注入势垒（φ(e)(聚合物/Alq3)或电子/激子阻挡势垒）。
