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News — Solution-processed quantum dots (QDs) light emitting diodes (QLEDs) have attracted enormous interests as an excellent candidate for display and lighting applications owing to their outstanding advantages, such as size-tunable emission wavelengths, near-unity quantum yield (QY), and high color purity. QLEDs produce significantly less heat compared to thermal radiation light sources. However, the suboptimal energy landscape of QLEDs and low thermal-conductivity of the functional layer materials can still lead to unavoidable heat accumulation, especially in high brightness areas, which can result in a roll-off in device efficiency and deterioration in operational lifetime.

In a new published in , a team of scientists, led by Professor Huaibin Shen from Key Laboratory for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High-efficiency Display and Lighting Technology, Henan University, 475004 Kaifeng, China and co-workers have developed the novel giant full-alloy CdZnSe/ZnSeS QDs to suppress the valence-band degeneracy. The CdZnSe-based QDs reveal a suppressed ground-state band splitting and high electron concentration. The CdZnSe-based QLEDs exhibit a dramatically reduced driving voltage with EQE larger than 25%, correspondingly, a wide luminance range of 200-30,000 cd m^-2. In addition to effectively inhibiting the efficiency roll-off, the CdZnSe-based devices show an excellent T₉₅ operation lifetime exceeding 70,000 hours at 1,000 cd m^-2 due to the effectively suppressed joule heat generation. Our strategy provides an efficient path to minimize heat generation and improve device stability.

The ground-state band splitting strategy effectively flattens the energy landscape of the interface between QDs and hole transport layer, which significantly facilitates the hole injection and accelerates the radiative recombination of excitons, which signifies the enhancement of carrier injection balance. In addition, CdZnSe-based QLEDs reveal a high electron concentration and a reduced and broad driving voltage, which decreases joule heat generation.

This significantly inhibits efficiency roll-off and achieves the record-high brightness at low drive voltage for CdZnSe-based devices. These results represent the best values of conventional QLEDs to date, without any light out-coupling structure and engineering of the emitter dipole. The scientists forecast that our strategy is also expected to achieve breakthrough progress for blue and green QLEDs, and other photoelectric devices.

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Funding information

This work was supported by the National Natural Science Foundation of China (Grant No. 22205054, U22A2072, 61922028, 22175056, and 22479041), Zhongyuan High Level Talents Special Support Plan (No. 244200510009), the National Key R&D Program of China (Grant No. 2023YFE0205000), and Postdoctoral Research Grant in Henan Province (No. 202103041).

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