Interface Engineering with Quaternary Ammonium-Based Ionic Liquids toward Efficient Blue Perovskite Light-Emitting Diodes

Perovskite light-emitting diodes (PeLEDs) have become a hot research topic in recent years and can now achieve an external quantum efficiency (EQE) of over 22% for green and red devices. However, the efficiency of blue PeLEDs, which are essential for display applications, lags far behind their green and red counterparts. The interface of the PeLEDs has a critical influence on the carrier transport and exciton recombination dynamics, and interface engineering is considered to be an effective strategy to improve the device performance. Herein, quaternary ammonium-based ionic liquids serve as an interfacial modification layer to significantly improve the device efficiency and stability. The interaction of quaternary ammonium cations with Pb(Br/Cl)6 octahedra promotes nucleation sites, which significantly improves the morphology of perovskite films and reduces the formation of defects in films. In addition, ion migration is also effectively suppressed in the device. As a result, with tributylmethylammonium bromide (TMAB) used as the interface layer, the EQE of the device is successfully increased from 3.5 to 6.7%, and the operational stability with a half-lifetime (T50) is increased by over 12 times. Our work provides a new class of interface modification materials toward high-performance blue PeLEDs.