One-step rapid synthesis for bright light emitting halide perovskites

Halide perovskites are promising materials for solar energy conversion and optoelectronic uses such as light-emitting devices, photodetectors and lasers. A class of these materials with the general formula A₄BX₆ are promising candidates that can extend the color spectrum and increase the brightness in light emitting devices. However, existing synthesis methods to produce A₄BX₆ materials often require long times, high temperatures and complicated reaction steps.

Jiang et al. report a one-step rapid synthesis technique for Cs₄PbBr₆ crystals that uses only a trace amount of solvent in a relatively short amount of time. The resulting crystals have high purity and produce green light of a brightness level well beyond that found in commercial phosphors.

To synthesize Cs₄PbBr₆, the investigators placed a small amount of CsBr and PbBr₂ in a test tube and added tiny amounts of dimethyl sulfoxide (DMSO). After sealing the test tube, they sonicated it using an ultrasonic cleaner. After 20 minutes, a pure yellow-green powder was obtained. Further investigation with scanning electron microscopy revealed well-formed crystals of Cs₄PbBr₆.

Other solvents did not produce good results. “We could not synthesize Cs₄PbBr₆ crystals with other solvents, such as water or isopropanol,” said author Qinglong Jiang. “The polarity of DMSO is very high, which makes it a better solvent for this reaction.”

To demonstrate the practical use of these crystals, the investigators assembled a device using commercially available Europium-containing substances with the Cs₄PbBr₆ crystals to produce a unit that emits bright white light. The emitted light has a sharp peak in the green region from the Cs₄PbBr₆ crystals, and the full device achieves a wide gamut of color coverage, opening up possibilities for further development.

Source: “Ultrasonication-assisted trace amount solvent synthesis of Cs₄PbBr₆ crystal with ultra-bright green light emission,” by Jintian Jiang, Daoyuan Wang, Mingfan Wu, Ping Peng, Fang-Fang Li, Faqian Liu, Renwei Jing, Xuedan Ma, Yan Chao, Zhili Xiao, and Qinglong Jiang, APL Materials (2020) The article can be accessed at https://doi.org/10.1063/5.0009852 .