Highly Efficient and Stable CsPbI 3 Perovskite Quantum Dots Light‐Emitting Diodes Through Synergistic Effect of Halide‐Rich Modulation and Lattice Repair

Currently, CsPbI₃ quantum dots (QDs) based light-emitting diodes (LEDs) are not well suited for achieving high efficiency and operational stability due to the binary-precursor method and purification process, which often results in the nonstoichiometric ratio of Cs/Pb/I. This imbalance leads to amounts of iodine vacancies, inducing severe non-radiative recombination processes and phase transitions of QDs. Herein, red-emitting CsPbI₃ QDs are reported with excellent optoelectronic properties and stability based on the synergistic effects of halide-rich modulation passivation and lattice repair. First, a ternary-precursor method is employed to better control the feed ratio of Cs/Pb/I and create a halide-rich environment. Second a solvent-free solid-liquid reaction employing a multifunctional guanidinium iodide (GAI) additive is used after purification to repair iodine vacancies and partially replace surface Cs atoms, thereby effectively modifying its tolerance factor. Additionally, this short-chain GA⁺ can be used as the surface ligand to improve the conductivity of the QDs and suppress trap-assisted non-radiative Auger recombination. Consequently, PeLEDs based on GAI-QDs exhibit a great maximum external quantum efficiency (EQE) of 27.1% and an operational half-lifetime (T₅₀) of 1001.1 min at an initial luminance of 100 cd m^-2.