期刊
ACS NANO
卷 16, 期 8, 页码 12866-12877出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.2c05130
关键词
Continuous-Wave Optically Detected Magnetic Resonance; Colloidal Quantum Dots; Semiconductors; Photoluminescence; Copper-Doped; Core; Shell
类别
资金
- USA/Israel Binational Science Foundation [2016156, 2020076]
- joint USA National Science Foundation - USA/Israel Binational Science Foundation (NSF-BSF) [2017637]
- Israel Science Foundation [2528/19, 1045/17]
- UW Molecular Engineering Materials Center, an NSF Materials Research Science and Engineering Center [DMR-1719797]
- NSF Materials Research Science and Engineering Center [DMR-1807394]
- NSF [DMR-1807394]
- Netherlands Organization for Scientific Research (NWO) [DMR-1807394]
- [14614]
This study elucidates the recombination processes and spin properties of copper-doped CdSe/CdS and CuInS2 colloidal quantum dots (CQDs) using optically detected magnetic resonance spectroscopy. The findings support different models for the magneto-optical properties of these important materials.
Copper-doped II-VI and copper-based I-III-VI2 colloidal quantum dots (CQDs) have been at the forefront of interest in nanocrystals over the past decade, attributable to their optically activated copper states. However, the related recombi-nation mechanisms are still unclear. The current work elaborates on recombination processes in such materials by following the spin properties of copper-doped CdSe/CdS (Cu@CdSe/CdS) and of CuInS2 and CuInS2/(CdS, ZnS) core/shell CQDs using continuous-wave and time-resolved optically detected magnetic resonance (ODMR) spectroscopy. The Cu@CdSe/CdS ODMR showed two distinct resonances with different g factors and spin relaxation times. The best fit by a spin Hamiltonian simulation suggests that emission comes from recombination of a delocalized electron at the conduction band edge with a hole trapped in a Cu2+ site with a weak exchange coupling between the two spins. The ODMR spectra of CuInS2 CQDs (with and without shells) differ significantly from those of the copper-doped II-VI CQDs. They are comprised of a primary resonance accompanied by another resonance at half-field, with a strong correlation between the two, indicating the involvement of a triplet exciton and hence stronger electron-hole exchange coupling than in the doped core/shell CQDs. The spin Hamiltonian simulation shows that the hole is again associated with a photogenerated Cu2+ site. The electron resides near this Cu2+ site, and its ODMR spectrum shows contributions from superhyperfine coupling to neighboring indium atoms. These observations are consistent with the occurrence of a self-trapped exciton associated with the copper site. The results presented here support models under debate for over a decade and help define the magneto-optical properties of these important materials.
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