Xia Huangad, Rongmei Yuc, Xingqiang Yangc, Xiumei Xuc, Han Zhangd, Dandan Zhangbe
Thickness of layers in improved QLEDs measured with CoreAFM
This study shows that the efficiency of quantum dot light emitting diodes (QLEDs) can be significantly increased by adding an additional layer of 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi, 3 nm) between the CuInS2/ZnS emission layer and the 4,4-N,N-dicarbazole-biphenyl (CBP) hole transport layer (HTL). The intermediate TPBi layer serves to reduce quenching of quantum dot (QD) emission and prevents leakage between the other layers. The Nanosurf CoreAFM was used to determine the thickness of each individual layer. The efficiency increases with the thickness, whereas the luminescence drops, explained by changes in the electron carrier distribution in the QD layers.