Water-Stable Zero-Dimensional (C₄H₉)₄NCuCl₂ Single Crystal with Highly Efficient Broadband Green Emission

Abstract

Here, we report (C₄H₉)₄NCuCl₂ single crystals with a luminous intensity that remains largely the same after soaking in water for 24 h. (CH₉)₄NCuCl₂ has a new type zero-dimensional framework, in which the isolated [CuCl₂]^- anions are wrapped by organic (C₄H₉)₄N⁺ cations. As expected, (C₄H₉)₄NCuCl₂ shows a broad emission band at 508 nm with a photoluminescence quantum yield of approximately 82% at room temperature, stemming from self-trapped exciton (STE) emission. Temperature-dependent photoluminescence measurement reveals that there is an energy barrier Δ<i>E</i> (24.0 meV) between the intrinsic state and STE state, which leads to the increase in emission intensity with an increase in temperature (98-278 K), while the emission intensity begins to decrease when the temperature is higher than 278 K due to the effects of both thermal quenching and carrier scattering. Our findings provide a new idea for the design of lead-free anti-water stability metal halide materials.