Department of Materials Science and Engineering, University of Florida , Gainesville, Florida 32611, United States.
Nano Lett. 2015 Feb 11;15(2):1211-6. doi: 10.1021/nl504328f. Epub 2015 Jan 13.
We report high-efficiency blue-violet quantum-dot-based light-emitting diodes (QD-LEDs) by using high quantum yield ZnCdS/ZnS graded core-shell QDs with proper surface ligands. Replacing the oleic acid ligands on the as-synthesized QDs with shorter 1-octanethiol ligands is found to cause a 2-fold increase in the electron mobility within the QD film. Such a ligand exchange also results in an even greater increase in hole injection into the QD layer, thus improving the overall charge balance in the LEDs and yielding a 70% increase in quantum efficiency. Using 1-octanethiol capped QDs, we have obtained a maximum luminance (L) of 7600 cd/m(2) and a maximum external quantum efficiency (ηEQE) of (10.3 ± 0.9)% (with the highest at 12.2%) for QD-LEDs devices with an electroluminescence peak at 443 nm. Similar quantum efficiencies are also obtained for other blue/violet QD-LEDs with peak emission at 455 and 433 nm. To the best of our knowledge, this is the first report of blue QD-LEDs with ηEQE > 10%. Combined with the low turn-on voltage of ∼2.6 V, these blue-violet ZnCdS/ZnS QD-LEDs show great promise for use in next-generation full-color displays.
我们通过使用具有适当表面配体的高荧光量子产率 ZnCdS/ZnS 分级核壳量子点，制备出高效率的蓝紫光量子点发光二极管（QD-LEDs）。将合成的量子点上的长链油酸配体替换为短链 1-辛硫醇配体，发现这会使量子点薄膜中的电子迁移率提高 2 倍。这种配体交换还会导致空穴更有效地注入到量子点层中，从而改善 LED 中的整体电荷平衡，使量子效率提高 70%。使用 1-辛硫醇封端的量子点，我们在 443nm 处获得了最大亮度（L）为 7600 cd/m²和最大外量子效率（ηEQE）为（10.3 ± 0.9）%（最高值为 12.2%）的 QD-LED 器件，电致发光峰位于 443nm。对于其他蓝/紫光 QD-LED，其峰值发射在 455nm 和 433nm 处，也获得了类似的量子效率。据我们所知，这是 ηEQE > 10%的蓝色 QD-LED 的首次报道。结合低开启电压约为 2.6V，这些蓝紫光 ZnCdS/ZnS 量子点 LED 有望用于下一代全彩显示器。
