Improved efficiency for lead-free CsCu2I3 halide microplatelets by suppressing surface pinholes via surface functionalization

Lead-free copper(I)-based halides have attracted tremendous attentions in producing optoelectronic devices due to their outstanding optical properties and low-cost synthesis. However, the low efficiency of copper(I)-based halides in the long-wavelength visible emissions (typically yellow- or red-light emissions) has hindered the use of such non-toxic halides in full-color displays and solid-state lighting applications. In this work, lead-free, air-stable and yellow-light emissive CsCu 2 I 3 microplatelets (MPs) with well-defined smooth surface were synthesized by a one-pot anti-solvent solution method at room temperature via surface functionalization with different long-chain surfactants . The results suggested that oleic acid (OA) was the most favorable surfactant for the CsCu 2 I 3 MPs with the best performance. Photoluminescence quantum efficiency of the yellow-emissive CsCu 2 I 3 MPs (centered at 580 nm) was dramatically enhanced fourfold by coordinating OA ligands during the synthesis to eliminate the surface pinholes of the CsCu 2 I 3 MPs. Notably, the CsCu 2 I 3 MPs showed ultra-high stability towards exposure of ambient air over 50 days. These findings may open new directions to synthetize high-efficiency copper(I)-based halides that generate long-wavelength visible emissions for lead-free nontoxic full-color optoelectronic devices.