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. 2020 Feb 18;11:937. doi: 10.1038/s41467-020-14756-5

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© The Author(s) 2020

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 2 — a Relative PL efficiency of the QDs in the QLEDs as a function of the driving voltage. b Relative PL efficiency of the CdSe/CdS-Cd(RCOO)₂ QDs in a QLED (driven at a constant voltage of 2 V for 50 h, followed by 0 V for 10 h). Insets are the corresponding photographs of the devices under ultraviolet irradiation (scale bar: 0.5 mm). c Relative PL efficiency of the QDs in electron-only devices (ITO/2,2’,2”-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi, ~25 nm)/QDs (~40 nm)/Zn_0.9Mg_0.1O (~60 nm)/Ag, driven at a constant current density of 10 mA cm⁻²). Inset, the relative PL efficiency of the QDs in hole-only devices (ITO/PEDOT:PSS (~35 nm)/poly-TPD (~30 nm)/PVK (~5 nm)/QDs (~40 nm)/4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP, ~25 nm)/MoO_x/Au) sharing the same coordinate axes with the main plot. The hole-only devices are driven at a constant current density of 30 mA cm⁻² to ensure that only holes and no electrons are injected into the devices. d, The voltammetric curves of the two types of CdSe/CdS core/shell QDs and cadmium oleate. e and f, PL and differential auger electron spectra of the CdSe/CdS-Cd(RCOO)₂ QDs in QLEDs under different conditions. The top electrodes are delaminated by adhesive tapes and the oxide electron-transporting layers are etched by a dilute acetonitrile solution of acetic acid, a known inert solution for the QD layer.