Phase Distribution Regulation of Thermally Evaporated Quasi-2D Perovskite Light-Emitting Diodes

Thermally evaporated quasi-two-dimensional (quasi-2D) perovskite light-emitting diodes (PeLEDs) offer a route toward next-generation display technology. However, their performance has lagged behind solution-processed devices. Here, we introduce an in situ phase regulation strategy by co-evaporating a multifunctional ligand, tris(trifluoromethyl)phosphine oxide (TFPPO). The fluorine atoms in TFPPO form hydrogen bonds with the N–H groups of phenylethylammonium (PEA), suppressing the disordered incorporation of PEA and slowing the crystallization of low-n phases. This interaction promotes a more uniform phase distribution and enhances exciton funneling through energy gradients. Besides, the P═O groups of TFPPO could also passivate undercoordinated Pb²⁺ defects. As a result, we achieved a record external quantum efficiency (EQE) of 17.5% among thermally evaporated PeLEDs. Furthermore, the optimized emissive layer is seamlessly integrated into a 6.67 in. active-matrix TFT-driven display panel, demonstrating the practical viability of this approach for scalable perovskite display technologies.