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 Cs4Pb(IxBr1–x)6/CsPb(IxBr1–x)3 heterostructures with a LiF interlayer. Excess CsI promotes 0D Cs4Pb(IxBr1–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 Pb2+ 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/m2, and T50 lifetime of 234 min at 1 mA/cm2. A 49 cm2 perovskite film shows uniform photoluminescence, confirming excellent scalability for a commercial pure-red display.