Department of Materials Science and Engineering and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign Urbana, Illinois 61801, United States.
ACS Nano. 2015 Jan 27;9(1):878-85. doi: 10.1021/nn506577p. Epub 2015 Jan 9.
Recent advances in colloidal quantum dot light-emitting diodes (QD-LEDs) have led to efficiencies and brightness that rival the best organic LEDs. Nearly ideal internal quantum efficiency being achieved leaves light outcoupling as the only remaining means to improve external quantum efficiency (EQE) but that might require radically different device design and reoptimization. However, the current state-of-the-art QD-LEDs are based on spherical core/shell QDs, and the effects of shape and optical anisotropy remain essentially unexplored. Here, we demonstrate solution-processed, red-emitting double-heterojunction nanorod (DHNR)-LEDs with efficient hole transport exhibiting low threshold voltage and high brightness (76,000 cd m(-2)) and efficiencies (EQE = 12%, current efficiency = 27.5 cd A(-1), and power efficiency = 34.6 lm W(-1)). EQE exceeding the expected upper limit of ∼ 8% (based on ∼ 20% light outcoupling and solution photoluminescence quantum yield of ∼ 40%) suggests shape anisotropy and directional band offsets designed into DHNRs play an important role in enhancing light outcoupling.
近年来，胶体量子点发光二极管（QD-LED）的发展使得其效率和亮度可与最佳有机发光二极管相媲美。几乎达到理想的内部量子效率，使得光取出成为提高外量子效率（EQE）的唯一途径，但这可能需要从根本上改变器件设计和重新优化。然而，目前最先进的 QD-LED 基于球形核/壳 QD，形状和光学各向异性的影响仍在本质上有待探索。在这里，我们展示了溶液处理的红色发射双异质结纳米棒（DHNR）-LED，具有高效的空穴传输，表现出低阈值电压、高亮度（76000 cd m-2）和高效率（EQE = 12%，电流效率 = 27.5 cd A-1和功率效率 = 34.6 lm W-1）。EQE 超过预期的上限（约 8%，基于约 20%的光取出和溶液光致发光量子产率约 40%）表明，DHNR 中的形状各向异性和定向能带偏移在增强光取出方面发挥了重要作用。
