Balanced Charge‐Carrier Transport and Defect Passivation in Far‐Red Perovskite Light‐Emitting Diodes

Abstract Perovskites are promising light emitters that can cover broad‐range emissions over the entire visible spectrum. However, few studies have focused on uncommon wavebands, such as far‐red emission of 700–750 nm that has broad applications in biology, horticulture lighting, optogenetics, etc. Here, a strategy is demonstrated to achieve high‐performance far‐red perovskite light‐emitting diodes (PeLEDs) through antisolvent engineering. First, 1,3,5‐tris(1‐phenyl‐1H‐benzimidazole‐2‐yl) benzene (TPBi) is introduced into n‐i‐p perovskite matrix not only to passivate the defects but also to balance carrier mobility as well as adjust the energy level alignment between perovskite and the electron transport layer. The n‐type TPBi can prevent hole carriers’ movements in perovskite light emitters and enhance electron injection. Furthermore, the incorporation of TPBi uplifts the Fermi energy level of perovskites by 0.32 eV as well as diminishes the conduction band offset between zinc oxide (ZnO) and the perovskite emitters, hence alleviating the accumulation of charges at the interface. Consequently, the PeLEDs with TPBi‐modified perovskite emitters show an invariable far‐red emission peak at around 735 nm with a champion external quantum efficiency of 14.22%. This work makes up the far‐red emission of perovskite light‐emitting devices and boosts latent capacity of PeLEDs for future application.