Lead halide perovskites have shown exceptional performance in light‐emitting devices (PeLEDs), particularly in producing significant electroluminescence in sky‐blue to near‐infrared wavelengths. However, PeLEDs emitting pure‐blue light at 465–475 nm are still not satisfactory. Herein, efficient and stable pure‐blue PeLEDs are reported by controlling phase distribution, passivation of defects, as well as surface modifications using multifunctional phenylethylammonium trifluoroacetate (PEATFA) in reduced‐dimensional p‐F‐PEA2Csn−1Pbn(Br0.55Cl0.45)3n+1 polycrystalline perovskite films. Compared with 4‐fluorophenylethylammonium (p‐F‐PEA+) in the pristine films, phenylethylammonium (PEA+) has lower adsorption energy while interacting with perovskites, resulting in large‐n low‐dimensional perovskites, which can greatly facilitate charge transport within the low‐dimensional perovskite films. The interaction between the CO group in trifluoroacetate (TFA−) and perovskites significantly reduces defects in the perovskite films. Additionally, the electron‐giving CF3 group in TFA‐ uplifts surface potential in the films, resulting in smooth electronic injection in devices. The multifunctional additive strategy leads to elevated radiative recombination and efficient carrier transport in the films and devices. As a result, the devices exhibit a maximum external quantum efficiency (EQE) of 11.87% at 468 nm with stable spectral output, the highest reported to date for pure‐blue PeLEDs. Thus, this study extends the way for high‐efficiency pure‐blue LED with perovskite polycrystal films.

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.

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