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PbS/CdS Core–Shell Quantum Dots Suppress Charge Transfer and Enhance Triplet Transfer
Author(s) -
Huang Zhiyuan,
Xu Zihao,
Mahboub Melika,
Li Xin,
Taylor Jordan W.,
Harman W. Hill,
Lian Tianquan,
Tang Ming Lee
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201710224
Subject(s) - tetracene , quantum dot , ultrafast laser spectroscopy , rubrene , photon upconversion , quantum yield , photochemistry , materials science , acceptor , chemistry , spectroscopy , optoelectronics , anthracene , doping , fluorescence , optics , physics , quantum mechanics , condensed matter physics
Abstract A sub‐monolayer CdS shell on PbS quantum dots (QDs) enhances triplet energy transfer (TET) by suppressing competitive charge transfer from QDs to molecules. The CdS shell increases the linear photon upconversion quantum yield (QY) from 3.5 % for PbS QDs to 5.0 % for PbS/CdS QDs when functionalized with a tetracene acceptor, 5‐CT . While transient absorption spectroscopy reveals that both PbS and PbS/CdS QDs show the formation of the 5‐CT triplet (with rates of 5.91±0.60 ns −1 and 1.03±0.09 ns −1 respectively), ultrafast hole transfer occurs only from PbS QDs to 5‐CT . Although the CdS shell decreases the TET rate, it enhances TET efficiency from 60.3±6.1 % to 71.8±6.2 % by suppressing hole transfer. Furthermore, the CdS shell prolongs the lifetime of the 5‐CT triplet and thus enhances TET from 5‐CT to the rubrene emitter, further bolstering the upconverison QY.