On the degradation mechanisms of quantum-dot light-emitting diodes
Song Chen1, *（陈崧） Weiran Cao2, Taili Liu3, Sai-Wing Tsang3, Yixing Yang2, Xiaolin Yan2 & Lei Qian2, *（钱磊）
1 College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren’ai Road, Suzhou Industrial Park, Suzhou 215123 Jiangsu, China.
2 TCL Corporate Research, 1001 Zhongshan Park Road, Nanshan District, Shenzhen 518067 Guangdong, China.
3Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong SAR, China.
These authors contributed equally: Song Chen, Weiran Cao.
NATURE COMMUNICATIONS ， (2019) 10:765
The operating lifetime of blue quantum-dot light-emitting diodes (QLED) is currently a short slab for this emerging display technology. To pinpoint the origin of device degradation, here we apply multiple techniques to monitor the electric-field distribution and space-charge accumulation across the multilayered structure before and after lifetime tests. Evident by charge-modulated electro-absorption and capacitance-voltage characteristics, the excited electrons in blue quantum dots (QD) are prone to cross the type II junction between the QD emission layer and the electron-transporting layer (ETL) due to the offset of conduction band minimum, leading to space-charge accumulation and operating-voltage rise in the ETL. Therefore, unlike those very stable red devices, of which the lifetime is primarily limited by the slow degradation of hole-transporting layer, the poor lifetime of blue QLED originates from the fast degradation at the QD-ETL junction. Materials engineering for efficient electron injection is prerequisite for the boost of operating lifetime.