Cs-TFSI-Modified PEDOT:PSS Interface Engineering for High-Performance Sky-Blue Perovskite Light-Emitting Diodes: Achieving Optimal Energy Alignment and Defect Suppression

Despite remarkable advances in red/green perovskite counterparts, blue perovskite light-emitting diodes (PeLEDs) are still confronted with large interfacial barriers and charge injection imbalance induced by an energy level mismatch between charge transport layers and perovskite films, which severely deteriorate device performance. Herein, we proposed a strategy of incorporating cesium bis(trifluoromethanesulfonyl)imide (Cs-TFSI) into hole injection layer (HIL) poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS). This strategy not only enhances the carrier transport ability of HIL via reorganizing the molecular conformation of PEDOT chains and forming ordered PEDOT domains but also improves energy level alignment, thereby boosting minority carriers of holes and achieving a balance of holes and electrons. In addition, the sulfonate groups in TFSI – interact with Pb 2+ ions, therefore passivating interfacial defects and improving the crystallinity of perovskites. Using this approach, we achieved sky-blue PeLEDs with an emission peak at 484 nm, a half-lifetime of 182 s, and a remarkable enhancement in the external quantum efficiency (EQE) that reached 12.32%. This finding may inspire the rational design of efficient perovskite LEDs through interfacial modification approaches.