Stable white LEDs fabricated with lead bromide perovskites

White light emitting diodes (WLEDs) with a high color rendering index can reveal illuminated objects with enhanced clarity and can be used as lighting sources throughout a wide range of industrial applications. One promising material for WLEDs are metal halide perovskite quantum dots. However, when perovskites with different halides are mixed, anion exchange occurs between them, limiting efficiency, CRI, and stability of the WLEDs.

Gao et al. used three colors of phosphors containing the same anion of bromine to settle the issue of anion exchange. The researchers integrated blue emitting CsPbBr₃ nanoplatelets, green emitting CsPbBr₃ quantum dots, and red emitting Mn-doped PEA₂PbBr₄ with UV LED chips to create WLEDs.

“Usually, the bromine based perovskite emits green light or even blue light when reducing the dimension, but it cannot emit red light. So, metal ions of manganese were doped into the two-dimensional bromine-based perovskite to obtain the red light,” author Chun Sun said.

The choice of the phosphors eliminated the anion exchange reaction problem. The as-prepared WLEDs can produce white light ranging from “cool” to “warm” hue by adjusting the ratio of the phosphors and demonstrated good stability when increasing both current and working time.

The authors hope their research will stimulate further exploration of low cost, stable and high performance active materials and phosphors. They expect that further optimization of the device structure will increase the stability and the luminous efficiency.

Source: “High color rendering index and stable white light emitting diodes fabricated from lead bromide perovskites,” by Zhiyuan Gao, Xingyi Wang, Yufei Bai, Chun Sun, Hanxin Liu, Le Wang, Sijing Su, Kangkai Tian, Zi-Hui Zhang, and Wengang Bi, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5121800 .