Extending the Temperature and Time Operating Windows of CsPbI 3 Quantum Dots for Scalable Synthesis for LEDs

ABSTRACT Large‐scale manufacturing of CsPbI 3 quantum dots (QDs) is hindered by narrow thermal and temporal operating windows, where slight deviations in temperature or reaction time can induce size de‐focusing via Ostwald ripening and α‐to‐δ phase transformation, leading to performance loss and poor reproducibility. Here we demonstrate that phenylphosphonic acid (PPA), with its strong chelating capability and moderate acidity, creates a synergistic effect between robust coordination and etching, resulting in colloidal system stabilization and effective removal of overgrown particles, thereby extending the synthesis window for CsPbI 3 QDs in hot‐injection. As a result, the synthesis window is extended from less than 30 min to over 8 h without phase transition, and increases the temperature tolerance. The PPA‐stabilized QDs exhibit low Urbach energy (28.2 meV), high photoluminescence quantum yield (99.8%), and narrow emission bandwidth (34.5 nm) at 667 nm, indicating minimal defects. In light‐emitting devices, large‐scale synthesized QDs have a peak external quantum efficiency of 30.7%, showing the possibility of scaling up optoelectronic devices. By converting a fragile synthesis into a forgiving process window, the synergistic strategy for etch and strong bonding advances the industrial viability of red perovskite QD inks and devices.