In Situ Interface Reaction Enables Efficient Deep-Blue Perovskite Light-Emitting Diodes

The development of blue perovskite light-emitting diodes (PeLEDs) is critical for advancing next-generation display technologies. However, the fabrication of high-quality mixed-halide blue perovskites remains challenging due to their intrinsic vulnerability to high defect densities, ion migration, and inefficient charge transport. To address this, we introduce a rapid in situ interface reaction at the buried interface between the perovskite layer and the underlying poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) film. This engineered interface reaction represents a novel method for preparing high-quality deep-blue CsPb(Br/Cl)₃ films. By incorporating lithium salicylate (SAL) as a reaction initiator into the perovskite precursor, a proton exchange is triggered between PEDOT:PSS and SAL, resulting in the formation of a multifunctional PSS-Li interfacial layer. This layer modulates perovskite nucleation and growth, producing compact, uniform, and small-grained deep-blue perovskite films with reduced trap densities and enhanced quantum confinement. Combined with optimized charge dynamics, the resulting spectrally stable deep-blue PeLEDs achieve a record external quantum efficiency of 16.3% at 468 nm. This approach facilitates the successful integration of uniform and high-clarity active-matrix displays on thin-film transistor circuit substrates.