The electroluminescence performance of heavy-metal-free blue quantum dot (QD) light-emitting diodes (QLEDs) is much lower than that of state-of-the-art cadmium-based counterparts. Ecofriendly ZnSeTe QDs are an ideal alternative to cadmium-based blue QDs 1 , 2 , but face issues with colour impurity and inferior stability caused by the aggregated tellurium (Te n ≥2 ) that dominates compositional inhomogeneity 3 , 4 . Here we developed an isoelectronic control strategy using congeneric sulfur coordinated with triphenyl phosphite (TPP-S) to construct homogeneous ZnSeTeS QDs with pure-blue emissions and near-unity photoluminescence quantum yield. TPP with low electron-donating capability promotes the reactivity balance among anionic precursors, favouring the growth of QDs with uniform composition. The acceptor-like S with high electronegativity weakens the hole localization of the Te atoms by interfering with their surrounding carriers, thereby suppressing the formation of Te n ≥2 isoelectronic centres. Furthermore, the congeneric S increases the configurational entropy of the QDs and eliminates the stacking faults and oxygen defects, leading to improved structural stability and reduced non-radiative carrier density. Consequently, the resulting pure-blue QLEDs based on core–shell ZnSeTeS/ZnSe/ZnS QDs emitting at 460 nm show a high external quantum efficiency of 24.7%, a narrow linewidth of 17 nm, and long operational half-lifetime ( T 50 ) close to 30,000 hours at 100 cd cm −2 , rivalling state-of-the-art cadmium-based blue QLEDs.
Cao Fan,Wang Sheng,Chen Zhixin,Zhang Shizheng,Wu Qianqian,Zhang Jiaqi,Yang Xuyong
Quantum dots (QDs) have emerged as promising candidates for next-generation display owing to their exceptional optoelectronic properties. However, despite substantial advancements in QD synthesis, the blue-emitting QDs, especially heavy-metal-free blue ones, still underperform compared with their red and green counterparts. ZnSeTe QDs offer a viable ecofriendly alternative for blue emissions, but their performance is limited by spectrum broadening (linewidth >20 nm) and structural instability. These issues stem from compositional inhomogeneity, which is primarily induced by Te aggregation during synthesis. Recently, we realized the synthesis of homogeneous quaternary-alloyed ZnSeTeS QDs through a synergistic strategy of reactivity modulation and isoelectronic control. This Protocol enables precise bandgap tuning in the blue spectral region (450–475 nm) by controlling the Te ratio, while ensuring high color purity and stability of QDs. Furthermore, the as-prepared ZnSeTeS QDs exhibit outstanding electroluminescence performance, with a peak external quantum efficiency of 24.7% and half-life of 29,600 h at 100 cd cm −2 , and demonstrate strong potential for applications such as solid-state lighting and bioimaging owing to their high stability and low toxicity. Here we detail a synthesis Protocol for ZnSe 0.94 Te 0.03 S 0.03 /ZnSe/ZnS core/shell/shell QDs via a hot-injection method using zinc carboxylate and anionic phosphine precursor, systematically outlining the design and preparation of precursors and QDs, post treatments (including purifications) and characterization methods, including time-resolved photoluminescence spectroscopy. The entire process typically requires 11–12 h for QD synthesis and 6 h for characterizations, demanding only accessible chemistry knowledge and routine colloidal synthesis techniques.
Environmentally friendly ZnSeTe QDs are attractive candidates for next-generation display and lighting due to their excellent luminescence and composition tunability. However, the substantial reactivity disparity between Se and Te precursors often leads to inhomogeneous Te distribution within ZnSeTe QDs, limiting the color purity and luminescence stability. To overcome these challenges, we developed ZnSeTeS/ZnSe/ZnS gradient alloy QDs to alleviate lattice mismatch and reduce defects, improving the stability and color purity of QDs. The optimized green-emitting QDs exhibit a narrow size distribution (∼5.6 nm), a full width at half maximum (FWHM) of 33 nm, and a photoluminescence (PL) peak at 532 nm, closely approaching the green primary defined by the BT.2020 standard. By adjusting the Te and S incorporation ratios, the PL peaks of the QDs are widely tuned from 420 to 670 nm. Furthermore, through the combination of thiol-ligand exchange and UV lithography, high-precision patterning of the ZnSeTeS/ZnSe/ZnS QDs was achieved with a single pixel size of 20 µm × 20 µm × 2.5 µm, demonstrating broad application prospects in next-generation microdisplay applications such as AR/VR.
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