Lead-free Double Perovskite Cs₂ AgIn_0.9 Bi_0.1 Cl₆ Quantum Dots for White Light-Emitting Diodes

Perovskite-based optoelectronic devices have attracted considerable attention owing to their excellent device performances and facile solution processing. However, the toxicity and intrinsic instability of lead-based perovskites have limited their commercial development. Moreover, the provision of an efficient white emission from a single perovskite layer is challenging. Here, novel electrically excited white light-emitting diodes (WLEDs) based on lead-free double perovskite Cs₂ AgIn_0.9 Bi_0.1 Cl₆ quantum dots (QDs) without any phosphor are fabricated for the first time. Density functional theory calculations are carried out to clarify the mechanism of absorption and recombination in Cs₂ AgIn_0.9 Bi_0.1 Cl₆ with Bi-doping breaking the parity-forbidden transition of the direct bandgap. Microzone optical and electronic characterizations reveal that the broadband emission of Cs₂ AgIn_0.9 Bi_0.1 Cl₆ QDs originates from self-trapped excitons, and luminescent properties are unchanged after the film deposition. The QD-WLED exhibits excellent Commission Internationale de L'Eclairage color coordinates, correlated color temperature and relatively high color rendering index of (0.32, 0.32), 6432 K, and 94.5, respectively. The maximum luminance of 158 cd m^-2 is achieved by triphenylphosphine oxide passivation, and this lead-free QD-WLED exhibits a superior stability in ambient air with a long T₅₀ ≈48.53 min. Therefore, lead-free perovskite Cs₂ AgIn_0.9 Bi_0.1 Cl₆ QDs are promising candidates for use in WLEDs in the future.