Wang Ya-Kun, Wan Haoyue, Xu Jian, Zhong Yun, Jung Eui Dae, Park So Min, Teale Sam, Imran Muhammad, Yu You-Jun, Xia Pan, Won Yu-Ho, Kim Kwang-Hee, Lu Zheng-Hong, Liao Liang-Sheng, Hoogland Sjoerd, Sargent Edward H
Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, PR China.
J Am Chem Soc. 2023 Mar 22;145(11):6428-6433. doi: 10.1021/jacs.2c13677. Epub 2023 Mar 10.
Indium phosphide (InP) quantum dots have enabled light-emitting diodes (LEDs) that are heavy-metal-free, narrow in emission linewidth, and physically flexible. However, ZnO/ZnMgO, the electron-transporting layer (ETL) in high-performance red InP/ZnSe/ZnS LEDs, suffers from high defect densities, quenches luminescence when deposited on InP, and induces performance degradation that arises due to trap migration from the ETL to the InP emitting layer. We posited that the formation of Zn traps on the outer ZnS shell, combined with sulfur and oxygen vacancy migration between ZnO/ZnMgO and InP, may account for this issue. We synthesized therefore a bifunctional ETL (CNT2T, 3',3'″,3'″″-(1,3,5-triazine-2,4,6-triyl)tris(([1,1'-biphenyl]-3-carbonitrile)) designed to passivate Zn traps locally and and to prevent vacancy migration between layers: the backbone of the small molecule ETL contains a triazine electron-withdrawing unit to ensure sufficient electron mobility (6 × 10 cm V s), and the star-shaped structure with multiple cyano groups provides effective passivation of the ZnS surface. We report as a result red InP LEDs having an EQE of 15% and a luminance of over 12,000 cd m; this represents a record among organic-ETL-based red InP LEDs.
磷化铟（InP）量子点使发光二极管（LED）成为可能，这种二极管不含重金属，发射线宽窄，且具有物理柔韧性。然而，高性能红色InP/ZnSe/ZnS发光二极管中的电子传输层（ETL）ZnO/ZnMgO存在高缺陷密度，沉积在InP上时会淬灭发光，并导致由于陷阱从ETL迁移到InP发光层而引起的性能下降。我们推测，ZnS外壳上Zn陷阱的形成，以及ZnO/ZnMgO和InP之间硫和氧空位的迁移，可能是造成这个问题的原因。因此，我们合成了一种双功能电子传输层（CNT2T，3'，3'″，3'″″-（1,3,5-三嗪-2,4,6-三基）三（（[1,1'-联苯]-3-腈）），旨在局部钝化Zn陷阱，并防止层间空位迁移：小分子电子传输层的主链包含一个三嗪吸电子单元，以确保足够的电子迁移率（6×10 cm V s），具有多个氰基的星形结构可有效钝化ZnS表面。结果表明，红色InP发光二极管的外量子效率（EQE）为15%，亮度超过12,000 cd m；这在基于有机电子传输层的红色InP发光二极管中创下了记录。
