Electrically Driven White Light Emission from Intrinsic Metal–Organic Framework

Light-emitting diodes (LEDs) have drawn tremendous potential as a replacement of traditional lighting due to its low-power consumption and longer lifetime. Nowadays, the practical white LEDs (WLED) are contingent on the photon down-conversion of phosphors containing rare-earth elements, which limits its utility, energy, and cost efficiency. In order to resolve the energy crisis and to address the environmental concerns, designing a direct WLED is highly desirable and remains a challenging issue. To circumvent the existing difficulties, in this report, we have designed and demonstrated a direct WLED consisting of a strontium-based metal–organic framework (MOF), {[Sr­(ntca)­(H2O)2]·H2O}n (1), graphene, and inorganic semiconductors, which can generate a bright white light emission. In addition to the suitable design of a MOF structure, the demonstration of electrically driven white light emission based on a MOF is made possible by the combination of several factors including the unique properties of graphene and the appropriate band alignment between the MOF and semiconductor layer. Because electroluminescence using a MOF as an active material is very rare and intriguing and a direct WLED is also not commonly seen, our work here therefore represents a major discovery which should be very useful and timely for the development of solid-state lighting.发光二极管（Light-emitting diodes，LED）凭借低功耗、长寿命的显著优势，在替代传统照明的应用中展现出巨大潜力。当前实用化白光发光二极管（white LEDs，WLED）依赖于含稀土元素荧光粉的光子下转换技术，该技术路径限制了其应用性能、能源利用效率与成本效益。为应对能源危机与环境挑战，开发直接型白光LED不仅极具应用价值，同时也是一项极具挑战性的课题。为突破现有技术瓶颈，本研究设计并制备了一款直接型白光LED器件：该器件以锶基金属有机框架（metal–organic framework，MOF）{[Sr(ntca)(H₂O)₂]·H₂O}ₙ（1）、石墨烯（graphene）与无机半导体为组成单元，可实现明亮的白光发射。除金属有机框架结构的合理设计外，石墨烯的独特属性，以及金属有机框架与半导体层之间适配的能带对齐关系，共同促成了基于金属有机框架的电驱动白光发射的实现。由于以金属有机框架作为活性材料的电致发光研究极为罕见且极具研究价值，同时直接型白光LED也鲜有报道，本研究成果堪称一项重要突破，对固态照明领域的发展具有重要的实用价值与现实意义。