TY - JOUR
T1 - Enhanced properties of organic electroluminescent devices with cesium chloride ultra-thin layer
AU - Lü, Zhaoyue
AU - Deng, Zhenbo
AU - Hou, Ying
AU - Zhang, Xiuli
AU - Xu, Haisheng
N1 - Funding Information:
We gratefully acknowledge the financial support of Science and Technology Commission of Suzhou Municipality under Contract No. ZXG2012037 and National Natural Science Foundation of China under Contract Nos. 60977027 and 91123034 .
PY - 2013
Y1 - 2013
N2 - The effect of various positions and thicknesses of cesium chloride (CsCl) layer in organic light-emitting diodes is investigated. The basic device configuration is indium-tin-oxide (ITO)/N,N′-bis-(1-naphthl)-diphenyl-1, 1′-biphenyl-4,4′-diamine (NPB)/tris (8-hydroxyquinoline) aluminum (Alq3)/aluminum (Al). The following results are demonstrated. When the CsCl layer is placed at the Alq3/Al interface and closer to the Al cathode inside Alq3 layer, the effective barrier to electron injection is reduced due to the reaction between Cs and Al. As a result, the injection of electrons and holes is more balanced and the efficiency is enhanced from 1.83 to 3.49 cd/A. And as an electron injection layer, CsCl can be comparable with lithium fluoride (LiF). If the distance of the CsCl layer is more than 20 nm from Alq3/Al interface inside Alq3 layer, the luminance and efficiency are enhanced but the injection is not increased, which is attributed to trap sites induced by the CsCl layer. The decrease of luminance and efficiency is observed when the CsCl layer is located at the NPB/Alq3 interface. The reason is exciton quenching due to charge transfer from metal Cs to organic material Alq3. The CsCl layer inside NPB layer plays a role of hole blocking. More balanced injection of carriers is expected. Subsequently, both luminance and efficiency are enhanced by 34% and 60%, respectively. When the cathode of lithium fluoride (LiF)/Al is used, the device efficiency is also improved from 4.0 to 5.0 cd/A by inserting the CsCl layer inside NPB layer. However, the improvement is not observed for the device with the CsCl layer inserted inside Alq3 layer in LiF/Al-OLED.
AB - The effect of various positions and thicknesses of cesium chloride (CsCl) layer in organic light-emitting diodes is investigated. The basic device configuration is indium-tin-oxide (ITO)/N,N′-bis-(1-naphthl)-diphenyl-1, 1′-biphenyl-4,4′-diamine (NPB)/tris (8-hydroxyquinoline) aluminum (Alq3)/aluminum (Al). The following results are demonstrated. When the CsCl layer is placed at the Alq3/Al interface and closer to the Al cathode inside Alq3 layer, the effective barrier to electron injection is reduced due to the reaction between Cs and Al. As a result, the injection of electrons and holes is more balanced and the efficiency is enhanced from 1.83 to 3.49 cd/A. And as an electron injection layer, CsCl can be comparable with lithium fluoride (LiF). If the distance of the CsCl layer is more than 20 nm from Alq3/Al interface inside Alq3 layer, the luminance and efficiency are enhanced but the injection is not increased, which is attributed to trap sites induced by the CsCl layer. The decrease of luminance and efficiency is observed when the CsCl layer is located at the NPB/Alq3 interface. The reason is exciton quenching due to charge transfer from metal Cs to organic material Alq3. The CsCl layer inside NPB layer plays a role of hole blocking. More balanced injection of carriers is expected. Subsequently, both luminance and efficiency are enhanced by 34% and 60%, respectively. When the cathode of lithium fluoride (LiF)/Al is used, the device efficiency is also improved from 4.0 to 5.0 cd/A by inserting the CsCl layer inside NPB layer. However, the improvement is not observed for the device with the CsCl layer inserted inside Alq3 layer in LiF/Al-OLED.
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U2 - 10.1016/j.displa.2012.12.001
DO - 10.1016/j.displa.2012.12.001
M3 - Article
AN - SCOPUS:84873340528
SN - 0141-9382
VL - 34
SP - 69
EP - 74
JO - Displays
JF - Displays
IS - 1
ER -