Low‐Dimensional Phase Distribution of Quasi‐2D Perovskites Induced by Interfacial Effect Enables Efficient Blue Lighting‐Emitting Diodes

Abstract Although tremendous advances have recently been achieved in perovskite light‐emitting diodes (PeLEDs), development of the blue PeLEDs needed to achieve full‐color displays is far behind the red and green counterparts. Here, a simple and effective interface engineering strategy is reported to achieve efficient blue PeLEDs by modifying poly(3, 4‐ethylene dioxythiophene):polystyrene sulfonic (PEDOT:PSS) substrate with an amphiprotic molecule glycine. As a multifunctional additive, glycine can not only modulate the pH of PEDOT:PSS, but also trigger strong interfacial effect. Cooperative coordination and hydrogen bonding interactions between glycine and perovskite at the interface can passivate the interfacial defects and manipulate upper perovskite crystallization. Therefore, high‐quality perovskite films with grade‐distributed phases are obtained, enabling efficient cascade energy transfer and suppression of leakage current. The resulting PeLED exhibits the electroluminescence (EL) peak at 473 nm with a maximum external quantum efficiency (EQE) of 7.2%, which is ≈5.5 times that of the unmodified device. Realizing the regulation of low‐dimensional phase distribution of quasi‐2D perovskites through interfacial effect provides a reliable way to fabricate efficient blue PeLEDs.