High color purity blue quantum dot light-emitting diodes (QLEDs) have great potential applications in the field of ultra-high-definition display. However, the realization of eco-friendly pure-blue QLEDs with a narrow emission linewidth for high color purity remains a significant challenge. Herein, a strategy for fabricating high color purity and efficient pure-blue QLEDs based on ZnSeTe/ZnSe/ZnS quantum dots (QDs) is presented. It is found that by finely controlling the internal ZnSe shell thickness of the QDs, the emission linewidth can be narrowed by reducing the exciton-longitudinal optical phonon coupling and trap states in the QDs. Additionally, the regulation of the QD shell thickness can suppress the Förster energy transfer between QDs in the QLED emission layer, which will help to reduce the emission linewidth of the device. As a result, the fabricated pure-blue (452 nm) ZnSeTe QLED with ultra-narrow electroluminescence linewidth (22 nm) exhibit high color purity with the Commission Internationale de l'Eclairage chromatic coordinates of (0.148, 0.042) and considerable external quantum efficiency (18%). This work provides a demonstration of the preparation of pure-blue eco-friendly QLEDs with both high color purity and efficiency, and it is believed that it will accelerate the application process of eco-friendly QLEDs in ultra-high-definition displays.
Le Ma,Xiansheng Li,Xuehan Chen,Jingyu Li,Pengfei Liu,Changting Wei,Qingshan Ma,Leimeng Xu,Wenhua Zhang,Jizhong Song
Mixed halide CsPb(Br/Cl) 3 quantum dots (QDs) exhibit fine tunable blue light and narrow photoluminescence (PL) full-width at half-maximum (FWHM), which has attracted significant attention as a promising candidate to realize a new generation of blue light technology. However, the introduction of Cl − makes it very easy to be eroded by water in the environment, which will lead to deep-level defects and degrade the luminescence and stability of QDs. Here, we propose to introduce tetra- n -octylammonium oxalate (TOAOxa) to improve the water-resistance stability and exciton recombination of CsPb(Br/Cl) 3 QDs and QD-based light-emitting diodes (QLEDs). The oxalate ion (Oxa 2− ) of TOAOxa could form strong interaction with undercoordinated Pb 2+ on CsPb(Br/Cl) 3 QD surface, which was confirmed by FTIR and XPS analysis. Oxa 2− passivated QDs (Oxa-QDs) exhibited improved photoluminescence quantum yield (PLQY) and enhanced water-resistance stability compared to pristine QDs. For example, after soaking in water–acetone co-solvent for 1 h, Oxa-QDs can maintain the initial cubic morphology and 43.9% of initial PL intensity, while the morphology and luminescence of pristine QDs are almost damaged. Based on the above concept, the Oxa-QD-based QLED presented a maximum external quantum efficiency (EQE) of 4.0%, and operational lifetime (T 50 ) of 84 s, which was a 5-fold enhancement in EQE, and 7-fold enhancement in stability compared to pristine QLED, respectively. Besides, the Oxa-QD-based QLED exhibits better stability in high-humidity air. To sum up, the Oxa 2− passivation strategy has significantly improved the efficiency and water-resistant stability of QDs and devices and would rapidly promote the development of blue-emitting QDs.
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