Stabilizing the Buried Interface Phase for Perovskite LEDs with a Remarkable <i>T</i> ₉₀ Lifetime at 1000 nit

High-brightness operational stability is a major challenge for the commercialization of perovskite light-emitting diodes (PeLEDs). Using combined morphological and spectroscopic analyses, we determined that compositional heterogeneity at the buried interface significantly limits the device operational stability. To address this, a fluorinated small molecule salt is introduced into the hole transport layer to modulate the crystallization of the perovskite layer. The multifunctional interfacial modifier serves as a nucleation center to promote crystal growth and mitigate low-n phases, thereby creating a more robust buried interface. As a result, the PeLEDs achieve a high external quantum efficiency of 29.2% with a remarkably low driving voltage. More importantly, the devices exhibit a remarkable T 90 operational lifetime of 726 min at 1000 cd m –2 . This study demonstrates the critical role of the buried interface in phase modulation and stability enhancement, providing a viable strategy for developing stable and energy-efficient perovskite optoelectronic devices.