Effect of Hole Transporting Materials on Photoluminescence of CdSe Core/Shell Quantum Dots

Photoluminescence quenching of colloidal CdSe core/shell quantum dots in the presence of hole transporting materials was studied by means of steady state and time resolved photoluminescence spectroscopy. With increasing hole transporting materials concentration in the CdSe core/shell quantum dot Solution, the photoluminescence intensity and lifetime decreased gradually. The photoluminescence quenching of CdSe/ZnSe quantum dots with adding hole transporting material N,N'-bis(1-naphthyl)N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) is more efficient than N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4'-diamine (TPD). And compared with CdSe core/shell quantum dots with ZnSe shell. the ZnS shell is an effective one oil the surface of CdSe quantum dots for reducing photoluminescence quenching efficiency when interacting with hole transporting material TPD. Based on the analysis. there are two pathways in the photoluminescence quenching process: static quenching and dynamic quenching. The static quenching results from the decrease in the number of the emitting centers, and the dynamic quenching is caused by the hole transfer from quantum dots to hole transporting materials molecules. The efficiency of the photoluminescence quenching in CdSe core/shell quantum dots is strongly dependent on the structure of the shells and the HOMO levels of the hole transporting materials. The results are important for understanding the nature of quantum dots surface and the interaction of quantum dots and hole transporting materials.