Abstract: Tandem quantum-dot light-emitting diodes (TQLED), as an important extension of quantum-dot light-emitting diodes (QLED) technology, have achieved remarkable improvements in external quantum efficiency, brightness, and operational lifetime through the introduction of multiple emission units and charge generation layers. They have thus become a major research focus in the development of next-generation high-performance display devices. However, despite the substantial progress made in TQLED research, it still faces several critical challenges, such as imbalanced charge injection, poor compatibility with solution-processing techniques, insufficient environmental friendliness of materials, and inadequate stability of devices during long-term operation. This paper first introduces the basic structure and working principles of TQLED, compares its advantages over conventional single-layer QLED, and elaborates on the working principle of the charge generation layer as well as its key role in the collaborative operation of multiple emission units. Subsequently, focusing on inverted, conventional, multiple emission material-based, and other innovative tandem device structures, the paper conducts a systematic analysis of the research progress in improving device performance through different material systems, processing technologies, and structural designs. It also summarizes the breakthroughs achieved by TQLED in terms of efficiency, brightness, and stability. Finally, it identifies current challenges in TQLEDs and proposes potential future development pathways alongside research priorities from perspectives such as material innovation, structural optimization, and process refinement. Special emphasis is placed on the importance of developing environmentally friendly quantum dot materials, innovating solution-processing techniques, and constructing stable interface structures. These analyses aim to provide theoretical guidance and technical references for the subsequent technological development of TQLED, accelerating their transition from laboratory research to industrial application.

Key words: tandem, quantum-dots, light-emitting diodes, charge generation layer