Doped Zero‐Dimensional Cesium Zinc Halides for High‐Efficiency Blue Light Emission

All‐inorganic zero‐dimensional (0D) metal halides have recently received increasing attention due to their excellent photoluminescence (PL) performance and high stability. Herein, we present the successful doping of copper(I) into 0D Cs 2 ZnBr 4 . The incorporating of Cu + cations enables the originally weakly luminescent Cs 2 ZnBr 4 to exhibit an efficient blue emission centered at around 465 nm, with a high photoluminescence quantum yield (PLQY) of 65.3 %. Detailed spectral characterizations, including ultrafast transient absorption (TA) techniques, were carried out to investigate the effect of Cu + dopants and the origin of blue emission in Cs 2 ZnBr 4 :Cu. To further study the role of the A‐site cation and halogen, A 2 ZnCl 4 :Cu (A=Cs, Rb) were also synthesized and found to generate intense sky‐blue emission (PLQY≈73.1 %). This work represents an effective strategy for the development of environmentally friendly, low‐cost and high‐efficiency blue‐emitting 0D all‐inorganic metal halides.