A dual PO group additive and anti-solvent synergistic strategy enables efficient and stable quasi-2D red perovskite LEDs

Quasi-two-dimensional (quasi-2D) mixed iodine/bromine halide perovskites are promising emitters for cost-effective, high-efficiency red perovskite light-emitting diodes (PeLEDs). However, mixed-halide perovskites suffer from poor film quality and pronounced non-radiative losses, which hinder the improvement of device performance. To address these issues, we implement a synergistic anti-solvent-plus-additive protocol. High-volatility anti-solvents with different polarities and boiling points were introduced to rapidly remove residual solvents and improve film formation. Concurrently, a bifunctional conductive molecule, 2,7-bis(diphenylphosphoryl)-9,9'-spirobifluorene (SPPO13), containing two PO functional groups was incorporated into the anti-solvent as an additive to passivate Pb²⁺ defects and facilitate balanced charge injection. This approach yielded a red PeLED with an emission peak at 660 nm, a peak luminance (<i>L</i>_max) of 3084 cd m^-2 and a maximum external quantum efficiency (EQE_max) of 5.63%, with Commission Internationale de L'Eclairage (CIE) coordinates of (0.715, 0.282). Furthermore, device stability was significantly improved, showing a lifetime (<i>T</i>₅₀) of 39.65 h. These performance metrics are 2.71, 5.26, and 4.92 times those of the reference device (<i>L</i>_max is 1140 cd m^-2, EQE_max is 1.07%, and <i>T</i>₅₀ is 8.06 h), respectively. The results in this study provide a viable pathway toward high-efficiency and stable quasi-2D red PeLEDs.