Ranran Fan,Junpeng Qiao,Jiaxin Xu,Sujuan Feng,Guangqiang Liu
Due to the superiority of low cost, easy manufacture, and tunable light emission owing to the diversity of compositions and dimensionalities, the metal halides have appeared as a promising class of semiconductors. Nevertheless, the toxicity problem along with inherent instability of Pb-based metal halides greatly limits their large-scale applications. Based on this situation, it is necessary to develop eco-friendly materials, which could simultaneously maintain the excellent optoelectronic properties of lead materials. In this Letter, the one-dimensional Cu + -alloyed Cs2AgI3 has been successfully synthesized. An intense blue emission located at 469 nm with a large Stokes shift was observed. Density functional theory calculation indicated that the Cu+ ions could effectively modulate the density of state population, which was the key factor drastically boosting the photoluminescence quantum yield (PLQY). This kind of highly efficient metal halide may overcome the bottlenecks of toxicity and poor efficiency issues of blue emission and will have a promising prospect in the optoelectronic fields.
Cesium lead halide perovskite nanocrystals (NCs) have attracted extensive attention for photoelectric device application due to their excellent optoelectronic properties. However, the toxicity of lead has hindered their commercialization. Consequently, lead free cesium metal halide NCs have been developed, but these materials suffer from low photoluminescence quantum yield (PLQY) and poor stability. Here, a new class of lead-free non-perovskite blue-emitting cesium bromine (CsBr) and cesium iodine (CsI) halide NCs are realized by zinc doping. High PLQYs of 79.05% and 78.95% are achieved by CsBr:Zn and CsI:Zn NCs, respectively, attributed to the improved local structural order and reduced strain between the lattices of the NCs after storing under ambient conditions for 20 to 30 days. Moreover, zinc doped cesium halide NCs show excellent air stability for at least 50 days. Our results for zinc doped cesium halide NCs have shown a new avenue to fabricate lead-free halide NCs for blue lighting and display applications.
Jingkun Xu,Shiming Guo,Junfeng Qu,Shuhong Xu,Chunlei Wang,Dayan Ban,Yiping Cui
All-inorganic cesium lead halide perovskite nanocrystals (NCs) are quite promising materials for emission-based applications. However, the intrinsic toxicity of lead, as well as the weak stability, remains to be resolved. Exploring more and more types of lead-free NCs with high photoluminescence quantum yields (PLQYs) and high stability is a fundamental task. This work gave the first example of copper doped cesium halide (Cu:CsX, X = Br, Cl/Br, Br/I) NCs with good stability and high PLQYs (∼31.2%), which could act as a new member of the lead-free NC family. A simple single-step ultrasonic method was applied for the synthesis of environmentally friendly Cu:CsX NCs. By varying the halide composition, the emission wavelength of Cu:CsX can be shifted within 450–505 nm. The as-prepared NCs show highly uniform size and excellent stability. Finally, UV pumped light-emitting diodes are demonstrated by using Cu:CsX NCs as a color conversion layer.
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