Zeng Yicheng, Yu Wenke, Liu Yuan, Chen Weiwei, Wang Qingya, Cao Fan, Wei Jing, Liu Fangze, Yang Xuyong, Li Hongbo
Experimental Center of Advanced Materials, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081, China.
Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai, 200072, China.
Adv Mater. 2025 Feb;37(5):e2415569. doi: 10.1002/adma.202415569. Epub 2024 Dec 8.
Anisotropic nanoplatelets (NPLs) possess strong in-plane transition dipole moments and out-of-plane emission, which enable a maximum photon out-coupling efficiency of 40% and a high gain coefficient, making them ideal candidates for light-emitting diodes (LEDs) and lasers. However, the unbalanced surface energy between the side and top facets of NPLs results in poor thermal stability and high susceptibility to ripening at elevated temperatures, which complicates the growth of the shell. To address this issue, a gradient crown (CdSeS) around the CdSe NPLs is designed to stabilize the high energy side facets. Consequently, the gradient alloyed shell (CdZnS) is successfully grown, and the CdSe/CdSeS/CdZnS core/crown/shell NPLs exhibited near-unity photoluminescence quantum yield. The CdSeS/CdZnS crown/shell structure suppressed non-radiative Auger recombinations, achieving a record-low amplification spontaneous emission threshold of 2.11 µJ cm under femtosecond laser excitation. In addition, by selecting the carrier transport layers with matched energy levels, the NPL-LEDs demonstrate a record-high external quantum efficiency of 30.1% in the pure-red range, driven by the 94% in-plane transition dipole moment distribution of NPL film. The NPL-LEDs also exhibited a long operational lifetime of T > 600 h at a luminance of 1000 cd m.
各向异性纳米片（NPLs）具有很强的面内跃迁偶极矩和面外发射特性，这使得其最大光子出耦合效率可达40%，且增益系数较高，使其成为发光二极管（LED）和激光器的理想候选材料。然而，NPLs侧面和顶面之间不平衡的表面能导致热稳定性差，在高温下极易熟化，这使得壳层生长变得复杂。为解决这一问题，在CdSe NPLs周围设计了一个梯度冠层（CdSeS）以稳定高能侧面。结果，成功生长出梯度合金壳层（CdZnS），且CdSe/CdSeS/CdZnS核/冠/壳NPLs表现出近乎单位的光致发光量子产率。CdSeS/CdZnS冠/壳结构抑制了非辐射俄歇复合，在飞秒激光激发下实现了创纪录的低放大自发发射阈值2.11 μJ/cm²。此外，通过选择能级匹配的载流子传输层，NPL-LEDs在纯红光范围内展示了创纪录的30.1%的高外量子效率，这是由NPL薄膜94%的面内跃迁偶极矩分布驱动的。NPL-LEDs在1000 cd/m²的亮度下还表现出T > 600 h的长工作寿命。
