Perovskite stacked LED external quantum efficiency exceeds 45%

Reporters learned from Nanjing University of Technology on the 12th that a scientific research team led by Huang Wei, academician of the Chinese Academy of Sciences and director of the National Key Laboratory of Flexible Electronics, successfully constructed an all-perovskite stacked light-emitting diode (LED) device, and innovatively proposed to use the interlayer photon circulation effect to improve the light extraction efficiency of perovskite LEDs. The external quantum efficiency of perovskite stacked LEDs exceeded 45%, refreshing the world record in this field and opening up a new way for the development of high-performance perovskite LEDs. The results were published in the international academic journal "Nature" on the 11th.

As the market demand for high-quality displays and lighting continues to increase, the development of new LED technology with high brightness, low cost and flexibility has become a research hotspot at the forefront of world science and technology.

Wang Nana, co-corresponding author of the paper and professor at the School of Flexible Electronics (Future Technology) of Nanjing University of Technology, said that perovskite LEDs have attracted much attention due to their advantages of solution processing, high color purity, and low preparation cost. Its current luminous efficiency is gradually approaching the level of commercial organic LEDs, and it has more advantages in brightness and color purity. At present, commercial organic LED display screens generally adopt a stacked device structure. By connecting multiple light-emitting units in series to achieve brightness superposition at the same current density, it has become a key path to improve the brightness and service life of LEDs.

However, the current external quantum efficiency of laminated perovskite LEDs is still less than 10%, which is even much lower than that of single-junction devices, seriously restricting their commercialization process.

In this study, the team achieved efficient charge injection and leveling in stacked devices by optimizing the connection layer structure. Wang Jianpu, co-corresponding author of the paper and professor at the National Key Laboratory of Flexible Electronics, said: "More importantly, by regulating the micro-nano structure of the perovskite light-emitting layer, we innovatively proposed a strategy to utilize the unique interlayer photon recycling effect in stacked devices. That is, the photons generated by one light-emitting unit can be reabsorbed and re-emitted by another perovskite layer, thereby breaking through the limitations of traditional light extraction efficiency and achieving the '1+1>2' effect."

Huang Wei, the co-corresponding author of the paper, said that this strategy enables the efficiency of stacked perovskite LED devices to reach commercial levels, and not only achieves the superposition of brightness of stacked devices, more groundbreakingly achieved synergy between light-emitting units, demonstrating the unique advantages of perovskite materials in constructing low operating voltage, high brightness, and high color purity stacked light-emitting devices.

Article source: Science and Technology Daily