title: Tunable Photoluminescent Core/Shell Cu(+)-Doped ZnSe/ZnS Quantum Dots Codoped with Al(3+), Ga(3+), or In(3+).
abstract: Semiconductor quantum dots (QDs) with stable, oxidation resistant, and tunable photoluminescence (PL) are highly desired for various applications including solid-state lighting and biological labeling. However, many current systems for visible light emission involve the use of toxic Cd. Here, we report the synthesis and characterization of a series of codoped core/shell ZnSe/ZnS QDs with tunable PL maxima spanning 430-570 nm (average full width at half-maximum of 80 nm) and broad emission extending to 700 nm, through the use of Cu(+) as the primary dopant and trivalent cations (Al(3+), Ga(3+), and In(3+)) as codopants. Furthermore, we developed a unique thiol-based bidentate ligand that significantly improved PL intensity, long-term stability, and resilience to postsynthetic processing. Through comprehensive experimental and computational studies based on steady-state and time-resolved spectroscopy, electron microscopy, and density functional theory (DFT), we show that the tunable PL of this system is the result of energy level modification to donor and/or acceptor recombination pathways. By incorporating these findings with local structure information obtained from extended X-ray absorption fine structure (EXAFS) studies, we generate a complete energetic model accounting for the photophysical processes in these unique QDs. With the understanding of optical, structural, and electronic properties we gain in this study, this successful codoping strategy may be applied to other QD or related systems to tune the optical properties of semiconductors while maintaining low toxicity.
authors.affiliation: †Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States.|‡Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Jason K
authors.initials: JK
authors.lastname: Cooper
authors.affiliation: †Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States.|§Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Sheraz
authors.initials: S
authors.lastname: Gul
authors.affiliation: †Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Lindley
authors.affiliation: §Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Junko
authors.initials: J
authors.lastname: Yano
authors.affiliation: †Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States.
authors.forename: Jin Z
authors.initials: JZ
authors.lastname: Zhang
keywords: QD-LED; ZnSe; doped; lifetime; passivation; quantum dot; shell