Interfacial Salt Engineering with Alkali and Ammonium Additives for Stable Pure-Blue Perovskite Light-Emitting Diodes...

Quasi-two-dimensional perovskites have emerged as promising candidates for high-quality blue-light emission in perovskite light-emitting diodes (PeLEDs). However, the efficiency of related devices is still limited by unbalanced crystallization in mixed-halide systems, where rapid nucleation at the interface creates defects that increase nonradiative losses, and the uncontrolled formation of low-dimensional phase disrupts energy funneling and exciton transfer. Herein, we introduce a salt-assisted interface engineering strategy that incorporates NH₄NO₃, Na₂SO₄, and KCl into the hole transport layer (HTL) to simultaneously regulate nucleation, crystal growth, and phase evolution. NH₄⁺, Na⁺, and K⁺ ions serve as interfacial nucleation sites that promote controlled, uniform crystallization, while the accompanying SO₄², NO₃^-, and Cl^- anions coordinate with undercoordinated Pb²⁺, suppressing defect formation and regulating the distribution of the quasi-2D phase. Pure-blue PeLEDs with the modified HTLs emit at 462, 463, and 469 nm, with maximum luminance values of 1035, 999, and 1087 cd/m² and EQEs of 9.09, 9.06, and 10.14%, respectively. Additionally, a transfer-enabled soft lithography approach was engineered to accomplish accurate and reproducible micropatterning of the perovskite emissive layer. Benefiting from this strategy, the HTL-modified micro-PeLEDs with a diameter and pitch of both 10 μm exhibit pure-blue emission with maximum luminance values of 546, 507, and 686 cd/m² and corresponding peak EQEs of 6.39, 6.30, and 6.80%, respectively.