Co‐Interlayer Engineering for Homogenous Phase Quasi‐2‐D Perovskite and High‐Performance Deep‐Blue Light‐Emitting Diodes

Abstract Organic and inorganic hybrid perovskites are a class of solution‐processable semiconductors that hold significant promise for light‐emitting diode applications. However, the development of efficient blue perovskite light‐emitting diodes (PeLEDs) has remained a critical challenge. Although significant advancements have been achieved in the development of sky‐blue PeLEDs, the performance of pure‐blue and deep‐blue PeLEDs still lags. In this manuscript, by incorporating 1‐cyclohexene‐1‐ethanamine cation (CEA + ) into the host 1‐phenylbutylamine cation (PBA + ) spacer and fabricating mixed‐cations quasi‐2D perovskites, a homogeneous phase distribution in quasi‐2D perovskite films is achieved through precise tuning of the phase formation energy. The resulting PeLEDs exhibit remarkable performance with an external quantum efficiency (EQE) of 5.8% at 467 nm, which is one of the highest EQEs among the deep‐blue light quasi‐2D PeLED devices with emission wavelengths below 470 nm, Additionally, the device demonstrates a half‐lifetime of ≈ 25 min. Furthermore, the PeLEDs utilizing mixed‐cation perovskite exhibit a stable electroluminescence (EL) spectrum under varying voltage biases, even when the chlorine content in the halogen sites reaches as high as 30%. Overall, this work offers a novel and promising avenue to achieve both high EQE and a stable EL spectrum in blue‐light quasi‐2D PeLEDs.