Buried Interface Engineering With Multifunctional Zwitterionic Additive for Efficient Blue Perovskite Light‐Emitting Diodes

ABSTRACT Blue perovskite light‐emitting diodes (PeLEDs) are a crucial breakthrough toward practical full‐color displays and solid‐state lighting. However, the widely used hole‐injection material, poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS), exhibits high acidity, a sizable energy‐level mismatch that hampers hole injection, and limited conductivity, which undermines device efficiency and operational stability. Herein, a facile buried interface engineering strategy is proposed to manipulate the nucleation and growth of perovskite films through the incorporation of a multifunctional, zwitterionic potassium taurate (KTAU) into PEDOT: PSS. The K + ions act as heterogeneous nucleation sites, promoting uniform surface coverage and preferred crystal orientation. The electron‐donating group SO 3 − can passivate the buried interface defects by coordinating with undercoordinated Pb 2+ and suppress the nonradiative recombination. In addition, the acid‐base neutralization eliminates the In species release from the indium tin oxide substrate, inhibiting exciton quenching at the PEDOT: PSS/perovskite interface. By reorganizing the molecular conformation of PEDOT: PSS, KTAU boosts PEDOT‐rich domains, improving band alignment of the perovskite layer. Benefiting from these synergistic effects, KTAU‐modified blue PeLEDs deliver a maximum external quantum efficiency (EQE) of 7.33%—3.1 × higher than the control one, together with prolonged operational lifetime. The results establish a grain‐growth substrate strategy for efficient and stable blue PeLEDs.