Removing Cadmium Impurities from Cation‐Exchange‐Derived CuInSe2/CuInS2 Nanorods for Enhanced Infrared Emission and Photodetection

Metal chalcogenide nanocrystals with variable composition and shape can conveniently be produced using cation exchange synthesis; however, the presence of cation‐containing ligands inherited from the starting material often results in contamination of the final product. To address this issue, a two‐...

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Bibliographic Details
Published in:Advanced functional materials 2024-08, Vol.34 (34), p.n/a
Main Authors: Portniagin, Arsenii S., Sergeev, Aleksandr A., Sergeeva, Kseniia A., Wang, Shixun, Li, Zhuo, Ning, Jiajia, Chan, Christopher C. S., Kershaw, Stephen V., Zhong, Xiaoyan, Wong, Kam Sing, Rogach, Andrey L.
Format: Article
Language:English
Subjects:
Cadmium
cation exchange
Cation exchanging
Copper indium selenides
Heterostructures
infrared photodetectors
ligand exchange
Ligands
Nanorods
Near infrared radiation
near‐infrared emission
Phosphonates
Photoluminescence
Room temperature
ternary chalcogenide nanorods
Wave functions
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Summary:Metal chalcogenide nanocrystals with variable composition and shape can conveniently be produced using cation exchange synthesis; however, the presence of cation‐containing ligands inherited from the starting material often results in contamination of the final product. To address this issue, a two‐step ligand replacement strategy is developed to fabricate CuInSe2/CuInS2 nanorods from CdSe/CdS nanorods via removal of Cd‐phosphonates from an intermediate Cu2‐xSe/Cu2‐xS phase used in the cation exchange conversion. This synthetic approach furnishes CuInSe2/CuInS2 nanorods with cadmium content below 1 at.%, and high photoluminescence quantum yields reaching 40% in the near‐infrared spectral range. Transient absorption studies reveal that the band alignment in the CuInSe2/CuInS2 heterostructure features a quasi‐type II character, with an electron localized in the core and a hole wavefunction spread over the entire nanorod. The efficient passivation of the core and the reduced Cd content leads to excitonic emission with full width at half maximum down to 110 meV, superimposed with a broad emission band from copper‐induced defects. Field‐effect transistors based on cadmium‐free CuInSe2/CuInS2 nanorods show two orders of magnitude lower noise current density compared with the cadmium‐rich devices. The responsivity and specific detectivity of these devices reach 230 mA W−1 and 108 Jones, respectively, under near‐infrared excitation at room temperature. A two‐step ligand exchange approach is applied to Cu2‐xSe/Cu2‐xS nanorods in order to remove cadmium ion impurities in the CuInSe2/CuInS2 nanorods produced by the cation exchange method. Low cadmium nanorods demonstrate PL QY up to 40% in the NIR range, while photodetectors based on them demonstrate detectivity as high as 108 Jones and high responsivity of 0.2 A W−1.
ISSN:1616-301X
1616-3028
DOI:10.1002/adfm.202400942