Bright Thermally Evaporated Red Perovskite Light-Emitting Diodes Enabled by In Situ Defect Passivation.

Thermally evaporated perovskite light-emitting diodes (PeLEDs) hold great promise for high-quality display applications due to their exceptional large-area uniformity and ease of pixelation and integration. Beyond efficiency considerations, display technologies demanded exceptionally high luminance performance from LEDs. While the brightness of blue and green PeLEDs had progressed rapidly, the performance of red PeLEDs lagged significantly. In this work, we achieved a breakthrough in bright thermally evaporated red PeLEDs through in situ defect passivation by coevaporating a molecular additive, 2,8-bis(diphenylphosphoryl)dibenzofuran (PPF), with PbI and CsBr. First-principles calculations revealed that PPF stabilized the outer electrons of the Pb atoms, effectively compensating for surface halide (I/Br) vacancies in CsPbIBr crystals. Experimental studies confirmed that PPF not only passivated defects but also enhanced film crystallinity and uniformity, leading to improved luminescence efficiency. When incorporated into PeLEDs, PPF enabled devices to achieve a record luminance of 3789 cd m for thermally evaporated red PeLEDs, along with stable deep-red emission at 650 nm, matching the Rec. 2020 standard for red emission.