Suppressing Efficiency Roll-Off at High Current Densities for Ultra-Bright Green Perovskite Light-Emitting Diodes
Suppressing Efficiency Roll-Off at High Current Densities for Ultra-Bright Green Perovskite Light-Emitting Diodes
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DOI：
10.1021/acsnano.0c01817
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发表时间：
2020-05-26
期刊：
影响因子：
17.1
通讯作者：
Lin, Lih Y.
中科院分区：
文献类型：
--
作者：
Zou, Chen;Liu, Yun;Lin, Lih Y.
近几年来，发光二极管（PeLED）得到了快速发展，其外量子效率（EQE）已达到21%以上。然而，大多数PeLED在高注入电流密度下仍然遭受严重的效率滚降（下降），从而限制了它们可实现的亮度，并对它们在激光二极管应用中的使用提出了挑战。在这项工作中，我们表明，滚降特性的PeLED的电荷注入不平衡，非辐射俄歇复合和焦耳加热的组合的影响。为了实现超亮和高效的PeLED，已经应用了几种策略。首先，我们设计了一个能量阶梯来平衡电子和空穴的输运。其次，我们优化了钙钛矿材料，以降低俄歇复合率并提高载流子迁移率。第三，我们用蓝宝石基板取代玻璃基板，以更好地消散焦耳热。最后，通过应用电流聚焦架构，我们实现了具有7.6Mcd/m（2）的创纪录亮度的PeLED。该装置可以在非常高的电流密度（J）下工作，最高接近1 kA/cm（2）。我们的工作表明钙钛矿材料在高亮度LED中具有广泛的应用前景，并最终有望用于溶液处理的电泵浦激光二极管。
Perovskite light-emitting diodes (PeLEDs) have undergone rapid development in the last several years with external quantum efficiencies (EQEs) reaching over 21%. However, most PeLEDs still suffer from severe efficiency roll-off (droop) at high injection current densities, thus limiting their achievable brightness and presenting a challenge to their use in laser diode applications. In this work, we show that the roll-off characteristics of PeLEDs are affected by a combination of charge injection imbalance, nonradiative Auger recombination, and Joule heating. To realize ultrabright and efficient PeLEDs, several strategies have been applied. First, we designed an energy ladder to balance the electron and hole transport. Second, we optimized perovskite materials to possess reduced Auger recombination rates and improved carrier mobility. Third, we replaced glass substrates with sapphire substrates to better dissipate joule heat. Finally, by applying a current-focusing architecture, we achieved PeLEDs with a record luminance of 7.6 Mcd/m(2). The devices can be operated at very high current densities (J) up to similar to 1 kA/cm(2). Our work suggests a broad application prospect of perovskite materials for high-brightness LEDs and ultimately a potential for solution-processed electrically pumped laser diodes.