Recently, Professor Jin Yizheng's research group from the Department of Chemistry at Zhejiang University, in collaboration with international research teams from Cambridge University, the University of Electronic Science and Technology of China in Chengdu, and other institutions, has made a breakthrough in the field of high-frequency response quantum dot light-emitting diodes (QLEDs).
This study is the first to report the memory effect of QLEDs under pulsed driving, revealing the regulation mechanism of quantum dot electroluminescence dynamics by deep-level traps in the organic charge transport layer. It innovatively transforms what was traditionally considered a material defect into a breakthrough for performance improvement, thus achieving the fastest-responding QLED to date. The relevant findings have been published online in *Nature Electronics*.
Quantum dot light-emitting diodes (QLEDs) are solution-processable electroluminescent devices with advantages such as low cost, high energy efficiency, and good stability, demonstrating great potential to replace traditional light sources in fields such as displays and lighting. However, due to the low mobility of the organic hole transport layer, the response speed (>microseconds) of QLEDs is difficult to match that of traditional III-V inorganic LEDs. This bottleneck severely limits the application of QLEDs in high-response-speed scenarios such as visible light communication and distance sensing.
The research team discovered that the response rate of QLEDs gradually increases under continuous pulse voltage excitation, exhibiting an ultrafast electroluminescence response with extremely low latency. These phenomena indicate that the transient emission of QLEDs is not an independent event, but a dynamic process modulated by the previous excitation history. Through time-correlated carrier dynamics simulations, they confirmed that the memory effect originates from the regulation of electroluminescence dynamics by deep-level trapping in the organic hole transport layer.
These deep-level traps have charge release time constants on the order of milliseconds. Under high-frequency, short-pulse conditions, incompletely released defect charges create a local electric field, confining some free carriers within the transport layer. When subsequent electrical pulses trigger QLED emission, the slow carrier injection and transport process can be bypassed, and ultrafast electroluminescence can be achieved directly using the free carriers confined in the transport layer.
Figure 1. Memory effect accelerates the response speed of QLEDs.
Building upon this foundation, the research team took a different approach, proposing a novel strategy of "memory effect accelerating device response," which significantly improved the response speed of QLEDs without increasing the driving voltage. Through process innovation, they constructed a novel micron-scale device (micro-QLED), significantly reducing device capacitance and compressing RC delay to nanoseconds. This resulted in groundbreaking performance records such as a 100MHz electroluminescence modulation frequency and a 120Mbps visible light communication transmission rate, while keeping the power consumption per bit below 1pJ.
Figure 2. Carrier dynamics of QLED ultrafast electroluminescence
This research transforms material defect states into positive factors that enhance device performance, opening up new avenues for high-frequency QLED applications. This approach of turning defects into advantages not only paves new paths for high-frequency QLED applications but also provides new ideas for the functional utilization of defect states in other optoelectronic material systems.
The findings, titled "Accelerated response speed of quantum-dot light-emitting diodes by hole-trap-induced excitation memory," were published in Nature Electronics (link: https://doi.org/10.1038/s41928-025-013500). Lu Xiuyuan, a doctoral student at Zhejiang University, and Dr. Deng Yunzhou (formerly a postdoctoral fellow at Zhejiang University and now a Mary Curie Scholar) from the University of Cambridge are co-first authors; Dr. Deng Yunzhou and Professor Jin Yizheng are co-corresponding authors. This research was supported by the National Key Research and Development Program of China and the Key Program of the Regional Innovation Development Joint Fund of the National Natural Science Foundation of China. (Source: Chemistry, Zhejiang University)
