Tunable and Patternable Quantum Dot Emissive Layers via Spray-Driven Surface Halide Exchange

All-inorganic CsPbX₃ quantum dots combine high efficiency, narrow emission, and solution processability, however, their scalable full-color implementation requires pixel-level patterning with minimal performance loss. Herein, we developed a spray-driven halide exchange strategy that enabled spatially programmable color tuning and patterning of green CsPbBr₃ films. By spraying a chlorine-based ligand through a mask, we obtained a surface-confined Br → Cl exchange, creating precise patterns without reprocessing the underlying film. After ligand exchange with phenethylammonium chloride (PEACl) at various concentrations, the photoluminescence peak shifted from 516 to 495/462/433 nm, while maintaining a full width at half maximum of approximately 20 nm. In addition, the crystalline phases and surface morphologies of the films were preserved. Furthermore, devices fabricated from halide exchange-treated films successfully converted the emission from green to blue. This strategy achieved an engineering tradeoff between pronounced color tuning and limited efficiency loss, providing a practical route for full-color pixelation on a single substrate.