高效稳定铜基钙钛矿的绿色制备技术及LED应用

近年来,卤化铅钙钛矿凭借其高吸收系数、大载流子扩散长度和优越的光电性能,在太阳能电池、发光二极管、光电探测器和激光器等领域获得了广阔的应用前景。然而,铅基钙钛矿的毒性和不稳定性限制了其进一步应用。因此,研究者们开始寻找替代铅的低毒或无毒元素,包括锡、铋、银、铟、锑、锗、铜等。

在新兴的无铅钙钛矿材料中,全无机铜基钙钛矿具有成本低、地球资源丰富等优点。但是,制备全无机铜基钙钛矿的合成方法很有限,且这些方法中还存在耗能、耗时、依赖溶剂等问题,并不符合环境友好型发展理念。

北京理工大学的陈冰昆副研究员在Photonics Research 2020年第6期的文章(Lingling Xie, Bingkun Chen, Fa Zhang, et al. Highly luminescent and stable lead-free cesium copper halide perovskite powders for UV-pumped phosphor-converted light-emitting diodes[J]. Photonics Research, 2020, 8(6): 06000768)中,介绍了全无机铜基Cs3Cu2X5(X=I,Cl)零维钙钛矿的绿色制备工艺。

作者采用简便易操作的干球磨法(一种绿色、节能的合成方法,已经被国际纯粹与应用化学联合会(IUPAC)确定为改变世界的十大技术之一)合成了荧光量子效率(PL QY)高达60%的全无机铜基Cs3Cu2X5零维钙钛矿。该制备方法不仅避免了溶剂的使用,而且通过对原料的控制,可在较短的时间内实现量产。

干球磨法制备的Cs3Cu2I5和Cs3Cu2Cl5全无机铜基零维钙钛矿粉末具有良好的热稳定性、光稳定性和空气稳定性。随后,作者以Cs3Cu2I5和Cs3Cu2Cl5全无机铜基零维钙钛矿粉末作为荧光粉,实现了紫外激发荧光转换型LED器件的制备。后续的工作主要从优化合成工艺、深入探究发光机理和拓展光电器件应用三个方面展开。

北京理工大学的王涌天教授认为,该制备方法有效避免了铅基钙钛矿的毒性和不稳定性等问题,并且发展了一种新的材料制备工艺,解决了难溶反应物的溶解度限制和水敏感反应物的局限性问题,为其他方法无法获得的材料铺平了道路。

以干球磨法合成的蓝光Cs3Cu2I5和绿光Cs3Cu2Cl5荧光粉,根据自限域发光机理实现了紫外激发荧光粉转换型LED器件的制备。

Highly luminescent and stable lead-free cesium copper halide perovskite powders for UV pumped phosphor converted light-emitting diodes

Lead halide perovskites have drawn extensive attention over recent decades owing to their advantages of high absorption coefficient, large carrier diffusion lengths, and superior photoelectric properties, which make them as promising candidates for solar cells, light-emitting diodes, photodetectors and lasers. However, their toxicity and instability as big issues need to be solved for further commercialization. So far, many efforts have been made to explore low- or non-toxic elements to replace lead, including tin (Sn), bismuth (Bi), silver (Ag), indium (In), antimony (Sb), germanium (Ge), and copper (Cu). Among these rising lead-free perovskite materials, all inorganic copper-based perovskites benefit from low cost and earth-abundant. In the previous reports, a limited number of synthetic methods have been used to fabricate copper based inorganic perovskites, and there are some problems in these methods, such as energy consumption, time consuming and solvent consuming, which is not accord with the concept of environment-friendly development.

Dr. Bingkun Chen who comes from a research group of Beijing Institute of Technology developed a facile dry ball milling method (preparation method of green and energy saving, which was identified by IUPAC as one of 10 world-changing technologies) to synthesize lead-free Cs3Cu2X5 (X=I, Cl) zero dimensional perovskites with photoluminescence quantum yield (PL QY) up to 60%. Dry ball milling method not only avoid the use of solvents, but also achieve high yield in a relatively short time by controlling raw materials. The as-synthesized Cs3Cu2I5 and Cs3Cu2Cl5 lead-free perovskite powders have good thermal stability, photostability and air stability. Furthermore, UV pumped phosphor converted light-emitting diodes were obtained by using Cs3Cu2I5 and Cs3Cu2Cl5 as phosphors. The research results are published in Photonics Research, Vol. 8, Issue 6, 2020 (Lingling Xie, Bingkun Chen, Fa Zhang, et al. Highly luminescent and stable lead-free cesium copper halide perovskite powders for UV-pumped phosphor-converted light-emitting diodes[J]. Photonics Research, 2020, 8(6): 06000768).

Future work will focus on the synthetic technology, photoluminescence mechanism and applications in the field of optoelectronic devices in order to fully explore and realize Cs3Cu2X5 perovskites.

Prof. Yongtian Wang from the Beijing Institute of Technology believes that this method not only provides copper based lead-free perovskite, but also develops a new material preparation technology, which avoids the solubility limitation of insoluble reactants and the limitation of water sensitive reactants, and paves the way for materials that cannot be obtained by other methods.

The blue emissive Cs3Cu2I5 and green emissive Cs3Cu2Cl5 synthesized by dry milling method were used as phosphors to prepare UV pumped phosphor converted light-emitting diodes.