3 years ago

Near-Infrared, Heavy Metal-Free Colloidal “Giant” Core/Shell Quantum Dots

Near-Infrared, Heavy Metal-Free Colloidal “Giant” Core/Shell Quantum Dots
Shuhui Sun, Haiguang Zhao, Xin Tong, Federico Rosei, Xiang-Tian Kong, Fabiola Navarro-Pardo, Yufeng Zhou, Gurpreet Singh Selopal, Zhiming M. Wang, Alexander O. Govorov
“Giant” core/shell quantum dots (g-QDs) are a promising class of materials for future optoelectronic technologies due to their superior chemical- and photostability compared to bare QDs and core/thin shell QDs. However, inadequate light absorption in the visible and near-infrared (NIR) region and frequent use of toxic heavy metals (e.g., Cd and Pb) are still major challenges for most g-QDs (e.g., CdSe/CdS) synthesized to date. The synthesis of NIR, heavy metal-free, Zn-treated spherical CuInSe2/CuInS2 g-QDs is reported using the sequential cation exchange method. These g-QDs exhibit tunable NIR optical absorption and photoluminescence (PL) properties. Transient fluorescence spectroscopy shows prolonged lifetime with increasing shell thickness, indicating the formation of quasi type-II band alignment, which is further confirmed by simulations. As a proof-of-concept, as-synthesized g-QDs are used to sensitize TiO2 as a photoanode in a photoelectrochemical (PEC) cell, demonstrating an efficient and stable PEC system. These results pave the way toward synthesizing NIR heavy metal-free g-QDs, which are very promising components of future optoelectronic technologies. Near-infrared (NIR), heavy metal-free, colloidal “giant” CuInSe2/CuInS2 core/shell quantum dots (QDs) are developed and their optical properties show tunable QD's absorption and photoluminescence (PL) spectra in NIR region (up to ≈1100 nm). The PL lifetime and simulation demonstrate their quasi type-II band alignment and corresponding QD-sensitized photoanode exhibits a saturated photocurrent density as high as ≈3.1 mA cm−2 with good stability.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201701432

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