Extending the Temperature and Time Operating Windows of CsPbI₃ Quantum Dots for Scalable Synthesis for LEDs

Large-scale manufacturing of CsPbI₃ 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 CsPbI₃ 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.