Chinese scientists from USTC created the most stable perovskite LEDs so far.
Paper in English:
Bright and stable perovskite light-emitting diodes in the near-infrared range
Abstract
Perovskite light-emitting diodes (LEDs) have attracted broad attention due to their rapidly increasing external quantum efficiencies (EQEs)
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. However, most high EQEs of perovskite LEDs are reported at low current densities (<1 mA cm−2) and low brightness. Decrease in efficiency and rapid degradation at high brightness inhibit their practical applications. Here, we demonstrate perovskite LEDs with exceptional performance at high brightness, achieved by the introduction of a multifunctional molecule that simultaneously removes non-radiative regions in the perovskite films and suppresses luminescence quenching of perovskites at the interface with charge-transport layers. The resulting LEDs emit near-infrared light at 800 nm, show a peak EQE of 23.8% at 33 mA cm−2 and retain EQEs more than 10% at high current densities of up to 1,000 mA cm−2. In pulsed operation, they retain EQE of 16% at an ultrahigh current density of 4,000 mA cm−2, along with a high radiance of more than 3,200 W s−1 m−2. Notably, an operational half-lifetime of 32 h at an initial radiance of 107 W s−1 m−2 has been achieved, representing the best stability for perovskite LEDs having EQEs exceeding 20% at high brightness levels. The demonstration of efficient and stable perovskite LEDs at high brightness is an important step towards commercialization and opens up new opportunities beyond conventional LED technologies, such as perovskite electrically pumped lasers.
News in Chinese:
“三高”近红外钙钛矿LED问世
科技日报合肥3月23日电 （记者吴长锋）23日，记者从中国科学技术大学获悉，该校崔林松教授课题组与国外同行合作，实现了兼具高亮度、高效率和高稳定性的近红外钙钛矿发光二极管，器件的最大外量子效率高达23.8%，器件预期寿命可达5万小时以上，器件性能达到国际领先水平，解决了该领域重要难题。相关研究成果日前发表于《自然》杂志。
崔林松介绍，“发光亮度、外量子效率和稳定性是决定钙钛矿LED走向商业化应用的关键指标。然而，目前报道的大多数近红外钙钛矿LED总是存在高亮度时效率太低、高效率下亮度太低的矛盾。如何在高亮度的同时保持高效率和高稳定性是钙钛矿LED领域亟须解决的难题，也是制约其商业化应用的关键技术瓶颈。”
在此次研究中，研究团队设计开发了一种多功能分子稳定剂2-（4-甲砜基苯基）乙胺（MSPE），用来精准调控钙钛矿材料的光电性能、晶体结构和形态学性质，大幅提升钙钛矿LED在高亮度下的效率和稳定性。一方面，MSPE通过氢键和配位键与钙钛矿中的组分相互作用，大幅提升钙钛矿薄膜的发光效率和发光均一性；另一方面，MSPE分子间通过氢键诱导形成自组装结构，消除了传输层界面对钙钛矿材料发光的淬灭。
得益于MSPE对钙钛矿和传输层界面的协同钝化效应，研究人员实现了高亮度、高效率和高稳定性的近红外钙钛矿LED。器件峰值外量子效率高达23.8%，并且在1000毫安/平方厘米的电流密度下，器件的外量子效率仍能超过10%，表现了超高的效率稳定性。器件预期寿命可达5万小时以上，在当前外量子效率超过20%的近红外钙钛矿LED中辐射亮度和稳定性都处于领先水平。
崔林松表示：“在高亮度下，实现高效稳定的钙钛矿LED是迈向商业化的关键一步，有望在未来进一步实现钙钛矿电泵浦激光器中展示出巨大潜力。”
审稿人评价该项工作：“团队设计开发了新颖的多功能分子稳定剂，制备了有史以来综合性能最优近红外钙钛矿LED，这些结果令人印象深刻，引起该领域研究人员的极大兴趣。”
