Sequential Stabilization for Color-Stable Deep-Blue Mixed-Halide Perovskite Light-Emitting Diodes

Perovskite light-emitting diodes (PeLEDs) have emerged as promising candidates for next-generation displays due to their low-cost fabrication and narrow emission bandwidths. Nonetheless, deep-blue PeLEDs still lag behind red and green devices in both efficiency and operational stability. Among various strategies for blue emission, including quantum confinement and wide-bandgap cation engineering, mixed-halide perovskites remain the most practical route to achieve deep-blue wavelengths. A key challenge in these systems arises from the weak ionic interaction between chloride (Cl–) and lead (Pb2+), which leads to a low formation energy of chloride vacancies. These vacancies serve as initiation sites for halide segregation, resulting in severe spectral instability under electrical bias. Although ligand-assisted precursor engineering can partially suppress vacancy formation, complete elimination remains difficult due to ligand loss during crystallization. Here, we present a solvent-compatible sequential stabilization (SCSS) strategy employing 3-(triphenylphosphonio) propane-1-sulfonate (TPPPS) on a propanesulfonate (PS)-treated perovskite layer. This strategy effectively neutralizes chloride vacancies and suppresses halide phase segregation, enabling spectrally stable deep-blue emission at 463 nm over a wide bias range, with an external quantum efficiency (EQE) of 9.4% and a maximum luminance (Lmax) of 353.2 cd/m2.