Lead-free violet-emitting K2CuCl3 single crystal with high photoluminescence quantum yield

Lead halide perovskites have attracted great attention on their promising luminescent properties. However, their practical use is hampered by the toxicity of Pb, and also the photoluminescence efficiency in violet region is much lower than green and red emitters. Herein, a new copper (I) halide with nontoxicity and efficient violet emission was synthesized and characterized. The major emission peak locates at 386 nm, the photoluminescence quantum yield reaches 98.8%, and the Stokes shift is as high as 1.15 eV K2CuCl3 crystal consists of one dimensional [CuCl4](3-) tetrahedral ribbons, which are isolated by K+ ions. The one dimensional crystal structure and the formation of self-trapped excitons, benefit the large thermal activation energy of 1090 meV, which contributes to the observed efficient emission.