Efficient All-Solution-Processed Perovskite Light-Emitting Diodes via a Room-Temperature Vapor-Treated Interlayer

Metal halide perovskites hold great promise for cost-effective, solution-processed, light-emitting diodes (LEDs) due to their exceptional optoelectronic properties. However, fabricating all-solution-processed perovskite LEDs (PeLEDs) remains challenging because the perovskite emitters are susceptible to damage from subsequent solution layers. Here, we introduce a novel fabrication method that employs a low-pressure-treated electron-transport layer (ETL) at room temperature, complemented by a polyethylenimine (PEI) interface modification layer. Notably, the optimized PEI-modified CsPbBr₃ exposed to air exhibits a remarkable 3-fold increase in photoluminescence intensity and maintains nearly constant light output for over 100 h, compared to pristine perovskite. Crucially, the incorporation of PEI significantly reduces the electron-transport barrier, mitigates the degradation of perovskite crystals caused by water and oxygen, and minimizes adverse interactions with solvents from the subsequent ETL. As a result, all-solution-processed PeLEDs incorporating an ETL subjected to a 20 min low-pressure treatment at 1 × 10^-1 mbar at room temperature achieved an unprecedented external quantum efficiency of up to 4.6%, a record low turn-on voltage of 2.1 V for CsPbBr₃, and an operational lifetime approximately 5 times longer than that of conventional devices. This strategy, both conceptually straightforward and easy to implement, offers a new avenue for the development of future printable PeLEDs.