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

All‐inorganic CsPbX 3 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 CsPbBr 3 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.