中国物理B ›› 2015, Vol. 24 ›› Issue (3): 37802-037802.doi: 10.1088/1674-1056/24/3/037802

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

Improvement of electron injection of organic light-emitting devices by inserting a thin aluminum layer into cesium carbonate injection layer

辛利文a b c, 吴晓明a b c, 华玉林a b c, 肖志慧a b c, 王丽a b c, 张欣a b c, 印寿根a b c   

  1. a School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384, China;
    b Key Laboratory of Display Materials and Photoelectric Devices of Ministry of Education, Tianjin 300384, China;
    c Tianjin Key Laboratory of Photoelectric Materials and Devices, Tianjin 300384, China
  • 收稿日期:2014-09-17 修回日期:2014-10-27 出版日期:2015-03-05 发布日期:2015-03-05
  • 基金资助:

    Project supported by the National Natural Science Foundation of China (Grant No. 60906022), the Natural Science Foundation of Tianjin, China (Grant No. 10JCYBJC01100), the Scientific Developing Foundation of Tianjin Education Commission, China (Grant No. 2011ZD02), the Key Science and Technology Support Program of Tianjin, China (Grant No. 14ZCZDGX00006), and the National High Technology Research and Development Program of China (Grant No. 2013AA014201).

Improvement of electron injection of organic light-emitting devices by inserting a thin aluminum layer into cesium carbonate injection layer

Xin Li-Wen (辛利文)a b c, Wu Xiao-Ming (吴晓明)a b c, Hua Yu-Lin (华玉林)a b c, Xiao Zhi-Hui (肖志慧)a b c, Wang Li (王丽)a b c, Zhang Xin (张欣)a b c, Yin Shou-Gen (印寿根)a b c   

  1. a School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384, China;
    b Key Laboratory of Display Materials and Photoelectric Devices of Ministry of Education, Tianjin 300384, China;
    c Tianjin Key Laboratory of Photoelectric Materials and Devices, Tianjin 300384, China
  • Received:2014-09-17 Revised:2014-10-27 Online:2015-03-05 Published:2015-03-05
  • Contact: Wu Xiao-Ming, Hua Yu-Lin E-mail:wxm@mail.nankai.edu.cn;yulinhua@tjut.edu.cn
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Grant No. 60906022), the Natural Science Foundation of Tianjin, China (Grant No. 10JCYBJC01100), the Scientific Developing Foundation of Tianjin Education Commission, China (Grant No. 2011ZD02), the Key Science and Technology Support Program of Tianjin, China (Grant No. 14ZCZDGX00006), and the National High Technology Research and Development Program of China (Grant No. 2013AA014201).

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摘要：

We investigate the electron injection effect of inserting a thin aluminum (Al) layer into cesium carbonate (Cs2CO3) injection layer. Two groups of organic light-emitting devices (OLEDs) are fabricated. For the first group of devices based on Alq3, we insert a thin Al layer of different thickness into Cs2CO3 injection layer, and the device's maximum current efficiency of 6.5 cd/A is obtained when the thickness of the thin Al layer is 0.4 nm. However, when the thickness of Al layer is 0.8 nm, the capacity of electron injection is the strongest. To validate the universality of this approach, then we fabricate another group of devices based on another blue emitting material. The maximum current efficiency of the device without and with a thin Al layer is 4.51 cd/A and 4.84 cd/A, respectively. Inserting a thin Al layer of an appropriate thickness into Cs2CO3 layer can result in the reduction of electron injection barrier, enhancement of the electron injection, and improvement of the performance of OLEDs. This can be attributed to the mechanism that thermally evaporated Cs2CO3 decomposes into cesium oxides, the thin Al layer reacts with cesium oxides to form Al-O-Cs complex, and the amount of the Al-O-Cs complex can be controlled by adjusting the thickness of the thin Al layer.

关键词: Al-O-Cs complex, Cs2CO3 electron injection layer, thin Al layer, organic light-emitting devices (OLEDs)

Abstract:

We investigate the electron injection effect of inserting a thin aluminum (Al) layer into cesium carbonate (Cs2CO3) injection layer. Two groups of organic light-emitting devices (OLEDs) are fabricated. For the first group of devices based on Alq3, we insert a thin Al layer of different thickness into Cs2CO3 injection layer, and the device's maximum current efficiency of 6.5 cd/A is obtained when the thickness of the thin Al layer is 0.4 nm. However, when the thickness of Al layer is 0.8 nm, the capacity of electron injection is the strongest. To validate the universality of this approach, then we fabricate another group of devices based on another blue emitting material. The maximum current efficiency of the device without and with a thin Al layer is 4.51 cd/A and 4.84 cd/A, respectively. Inserting a thin Al layer of an appropriate thickness into Cs2CO3 layer can result in the reduction of electron injection barrier, enhancement of the electron injection, and improvement of the performance of OLEDs. This can be attributed to the mechanism that thermally evaporated Cs2CO3 decomposes into cesium oxides, the thin Al layer reacts with cesium oxides to form Al-O-Cs complex, and the amount of the Al-O-Cs complex can be controlled by adjusting the thickness of the thin Al layer.

Key words: Al-O-Cs complex, Cs2CO3 electron injection layer, thin Al layer, organic light-emitting devices (OLEDs)

中图分类号:  (Electroluminescence)

  • 78.60.Fi
73.61.Ph (Polymers; organic compounds) 85.60.Jb (Light-emitting devices)