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Droop-Free Colloidal Quantum Dot Light-Emitting Diodes
Nano Letters ( IF 9.6 ) Pub Date : 2018-09-10 00:00:00 , DOI: 10.1021/acs.nanolett.8b03457 Jaehoon Lim 1, 2 , Young-Shin Park 1, 3 , Kaifeng Wu 1 , Hyeong Jin Yun 1 , Victor I. Klimov 1
Nano Letters ( IF 9.6 ) Pub Date : 2018-09-10 00:00:00 , DOI: 10.1021/acs.nanolett.8b03457 Jaehoon Lim 1, 2 , Young-Shin Park 1, 3 , Kaifeng Wu 1 , Hyeong Jin Yun 1 , Victor I. Klimov 1
Affiliation
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Colloidal semiconductor quantum dots (QDs) are a highly promising materials platform for implementing solution-processable light-emitting diodes (LEDs). They combine high photostability of traditional inorganic semiconductors with chemical flexibility of molecular systems, which makes them well-suited for large-area applications such as television screens, solid-state lighting, and outdoor signage. Additional beneficial features include size-controlled emission wavelengths, narrow bandwidths, and nearly perfect emission efficiencies. State-of-the-art QD-LEDs exhibit high internal quantum efficiencies approaching unity. However, these peak values are observed only at low current densities (J) and correspondingly low brightnesses, whereas at higher J, the efficiency usually exhibits a quick roll-off. This efficiency droop limits achievable brightness levels and decreases device longevity due to excessive heat generation. Here, we demonstrate QD-LEDs operating with high internal efficiencies (up to 70%) virtually droop-free up to unprecedented brightness of >100,000 cd m–2 (at ∼500 mA cm–2). This exceptional performance is derived from specially engineered QDs that feature a compositionally graded interlayer and a final barrier layer. This QD design allows for improved balance between electron and hole injections combined with considerably suppressed Auger recombination, which helps mitigate efficiency losses due to charge imbalance at high currents. These results indicate a significant potential of newly developed QDs as enablers of future ultrabright, highly efficient devices for both indoor and outdoor applications.
中文翻译：
无下垂的胶体量子点发光二极管
胶体半导体量子点（QD）是用于实施可溶液处理的发光二极管（LED）的极有前途的材料平台。它们结合了传统无机半导体的高光稳定性和分子系统的化学灵活性，这使其非常适合大面积应用，例如电视屏幕，固态照明和户外标牌。其他有益功能包括尺寸受控的发射波长，窄带宽和近乎完美的发射效率。最先进的QD-LED表现出接近于一体的高内部量子效率。但是，这些峰值仅在低电流密度（J）和相应的低亮度下观察到，而在较高的J下观察到，效率通常会快速下降。这种效率下降会限制可达到的亮度水平，并由于产生过多的热量而降低设备的使用寿命。在这里，我们演示了QD-LED能够以高内部效率（高达70％）工作，并且几乎不会下垂，亮度达到前所未有的> 100,000 cd m –2（在〜500 mA cm –2时））。这种出色的性能源于经过特殊设计的QD，这些QD具有成分分级的中间层和最终的阻隔层。这种QD设计可改善电子注入与空穴注入之间的平衡，并大大抑制俄歇复合，从而有助于减轻由于高电流下电荷不平衡引起的效率损失。这些结果表明，新开发的量子点具有巨大的潜力，可以用作未来超亮，高效的室内和室外应用设备的推动力。
更新日期：2018-09-10
中文翻译：
无下垂的胶体量子点发光二极管
胶体半导体量子点（QD）是用于实施可溶液处理的发光二极管（LED）的极有前途的材料平台。它们结合了传统无机半导体的高光稳定性和分子系统的化学灵活性，这使其非常适合大面积应用，例如电视屏幕，固态照明和户外标牌。其他有益功能包括尺寸受控的发射波长，窄带宽和近乎完美的发射效率。最先进的QD-LED表现出接近于一体的高内部量子效率。但是，这些峰值仅在低电流密度（J）和相应的低亮度下观察到，而在较高的J下观察到，效率通常会快速下降。这种效率下降会限制可达到的亮度水平，并由于产生过多的热量而降低设备的使用寿命。在这里，我们演示了QD-LED能够以高内部效率（高达70％）工作，并且几乎不会下垂，亮度达到前所未有的> 100,000 cd m –2（在〜500 mA cm –2时））。这种出色的性能源于经过特殊设计的QD，这些QD具有成分分级的中间层和最终的阻隔层。这种QD设计可改善电子注入与空穴注入之间的平衡，并大大抑制俄歇复合，从而有助于减轻由于高电流下电荷不平衡引起的效率损失。这些结果表明，新开发的量子点具有巨大的潜力，可以用作未来超亮，高效的室内和室外应用设备的推动力。
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