Thermally Evaporated 0D/3D Perovskite Heterostructures with LiF Interlayer for Spectrally Stable Pure-Red Perovskite Light-Emitting Diodes

Thermally evaporated perovskite light-emitting diodes (PeLEDs) offer high reproducibility and scalability, making them promising for next-generation displays. However, achieving spectrally stable pure-red mixed-halide PeLEDs that meet the Rec.2020 color standard remains challenging due to halide segregation and poor crystallinity. Here, we fabricated thermally evaporated pure-red PeLEDs by integrating 0D/3D Cs 4 Pb(I x Br 1– x ) 6 /CsPb(I x Br 1– x ) 3 heterostructures with a LiF interlayer. Excess CsI promotes 0D Cs 4 Pb(I x Br 1– x ) 6 formation and lattice expansion, facilitating wavelength tunability and improved optoelectronic performance via defect passivation and enhanced exciton binding. The LiF interlayer further mitigates interfacial defects as F – passivates undercoordinated Pb 2+ and halide vacancies, while Li + acts as a diffusion barrier to suppress halide migration, leading to reduced nonradiative recombination and excellent spectral stability. The optimized device achieves an EQE of 8.15%, luminance of 1786 cd/m 2, and T 50 lifetime of 234 min at 1 mA/cm 2 . A 49 cm 2 perovskite film shows uniform photoluminescence, confirming excellent scalability for a commercial pure-red display.