Vacuum-compatible phase engineering enables high-efficiency and color-pure green perovskite light-emitting diodes

Vacuum deposition offers a scalable, industry-compatible route for perovskite optoelectronics, yet efficient and spectrally stable emission remains limited by uncontrolled crystallization and defect-mediated nonradiative recombination. Here, we incorporate phenethylammonium bromide into a co-evaporated cesium bromide and lead bromide emissive layer for green vacuum-deposited perovskite light-emitting diodes. Phenethylammonium bromide regulates crystallization, modifies the local coordination environment, suppresses excessive grain growth, and improves film uniformity, thereby reducing trap-assisted recombination and enhancing radiative efficiency. The optimized devices achieve a maximum external quantum efficiency of 10.2%, a current efficiency of 36.5 cd A −1 , a power efficiency of 35.8 lm W −1 , and a luminance above 12,600 cd m −2 . The emission peaks at 518 nm with a full width at half maximum of 20 nm and remains spectrally stable under varying drive conditions. The devices exhibit an operational lifetime of 4388 s at an initial luminance of 500 cd m −2 .