Abstract Precise control of quantum structures in hybrid nanocrystals requires advancements in scientific methodologies. Here, on the design of tunable CsPbBr 3 /Cs 4 PbBr 6 quantum dots are reported by developing a unique discrete phase transformation approach in Cs 4 PbBr 6 nanocrystals. Unlike conventional hybrid systems that emit solely in the green region, this current strategy produces adjustable luminescence in the blue (450 nm), cyan (480 nm), and green (510 nm) regions with high photoluminescence quantum yields up to 45%, 60%, and 85%, respectively. Concentration‐dependent studies reveal that phase transformation mechanisms and the factors that drive CsBr removal occur at lower dilutions while the dissolution–recrystallization process dominates at higher dilutions. When the polymer‐CsPbBr 3 /Cs 4 PbBr 6 integrated into a field‐effected transistor the resulting phototransistors featured enhanced photosensitivity exceeding 10 5 , being the highest reported for an n ‐type phototransistor, while maintaining good transistor performances as compared to devices consisting of polymer‐CsPbBr 3 NCs.

Tunable Emissive CsPbBr3/Cs4PbBr6 Quantum Dots Engineered by Discrete Phase Transformation for Enhanced Photogating in Field‐Effect Phototransistors