Type-II CdSe/CdTe/ZnTe (core-shell-shell) quantum dots with cascade band edges: the separation of electron (at CdSe) and hole (at ZnTe) by the CdTe layer.
The rational design and synthesis of CdSe/CdTe/ZnTe (core-shell-shell) type-II quantum dots are reported. Their photophysical properties are investigated via the interband CdSe-->ZnTe emission and its associated relaxation dynamics. In comparison to the strong CdSe (core only) emission (lambda(max) approximately 550 nm, Phi(f) approximately 0.28), a moderate CdSe-->CdTe emission (lambda(max) approximately 1026 nm, Phi(f) approximately 1.2 x 10(-3)) and rather weak CdSe-->ZnTe interband emission (lambda(max) approximately 1415 nm, Phi(f) approximately 1.1 x 10(-5)) are resolved for the CdSe/CdTe/ZnTe structure (3.4/1.8/1.3 nm). Capping CdSe/CdTe with ZnTe results in a distant electron-hole separation between CdSe (electron) and ZnTe (hole) via an intermediate CdTe layer. In the case of the CdSe/CdTe/ZnTe structure, a lifetime as long as 150 ns is observed for the CdSe-->ZnTe (1415 nm) emission. This result further indicates an enormously long radiative lifetime of approximately 10 ms. Upon excitation of the CdSe/CdTe/ZnTe structure, the long-lived charge separation may further serve as an excellent hole carrier for catalyzing the redox oxidation reaction.
Chen
Chun-Yen
CY
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
Cheng
Chiu-Ting
CT
Lai
Chih-Wei
CW
Hu
Ya-Hui
YH
Chou
Pi-Tai
PT
Chou
Yi-Hsuan
YH
Chiu
Hsin-Tien
HT
D000042:Absorption; D019187:Cadmium Compounds / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004583:Electrons; D046529:Microscopy, Electron, Transmission; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D012666:Semiconductors; D013053:Spectrophotometry; D013691:Tellurium / Q000737:chemistry*; D013696:Temperature; D015032:Zinc / Q000737:chemistry*
D019187:Cadmium Compounds; D018036:Selenium Compounds; C058667:cadmium selenide; D015032:Zinc; D013691:Tellurium; C028337:cadmium telluride