Fluoride Interfaces Enhance the Performance of Perovskite Light-emitting Diodes

Perovskite light-emitting diodes (PeLEDs) have shown promises for future display and lighting applications. Significant advances were made in improving the external quantum efficiencies (EQEs) and operational stability. An important factor affecting PeLED performance is the limited selection of charge-transport materials. Recent studies indicated that the deposition of some fluoride compounds onto a hydrophobic hole-transport layer can enhance the performance of PeLEDs. However, the effects of fluoride interfaces on PeLEDs are not fully explored. In this work, four types of fluoride interlayers are investigated. Among them, LiF, MgF
2
and SrF
2
can enhance the photoluminescence quantum yields (PLQYs) of the perovskites and maintain a favorable film morphology on a hydrophobic hole-transport polymer (TFB). In contrast, the PLQYs of perovskites markedly reduce with a CsF interlayer. The thermally evaporated, discontinuous CsF layer cannot provide sufficient hydrophobicity for the perovskite deposition. Further, we demonstrate green PeLEDs with EQEs of > 17% and high luminance of > 10
⁵
cd m
⁻²
. Our results show that the extended range of fluoride interfaces presents additional opportunities for achieving high-performance PeLEDs.