title: 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.
abstract: 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.
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Chun-Yen
authors.initials: CY
authors.lastname: Chen
authors.forename: Chiu-Ting
authors.initials: CT
authors.lastname: Cheng
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Lai
authors.forename: Ya-Hui
authors.initials: YH
authors.lastname: Hu
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
authors.forename: Yi-Hsuan
authors.initials: YH
authors.lastname: Chou
authors.forename: Hsin-Tien
authors.initials: HT
authors.lastname: Chiu
mesh_terms: 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*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; C058667:cadmium selenide; D015032:Zinc; D013691:Tellurium; C028337:cadmium telluride