A Multifunctional Ionic Liquid Additive Enabling Stable and Efficient Perovskite Light-Emitting Diodes

The electroluminescence performance and long-term stability of perovskite light-emitting diodes (PeLEDs) are greatly affected by the film quality of perovskite emitting layer. Herein, the authors employ an ionic liquid, 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIm]OTf), to manipulate the growth of quasi-2D perovskite films by providing heterogeneous nucleation sites. The [BMIm]OTf molecules simultaneously realize uniform perovskite films by reducing the contact angles of precursor solution on the hole transport layer (HTL), and eliminate defect states through bonding [BMIm](+) cations to negatively-charged uncoordinated Br and OTf- anions to uncoordinated Pb2+ defects that effectively suppresses the defect states assisted nonradiative recombination in perovskite films. As a result, the efficiency and the operational lifetime of the resultant PeLED are enhanced by more than twofold and threefold, respectively, achieving a maximum external quantum efficiency of 17.6% and an operational lifetime of over 500 min at an initial brightness of 100 cd m(-2).

Automated summary

The electroluminescence performance and long-term stability of perovskite light-emitting diodes (PeLEDs) are greatly improved by using an ionic liquid to control the growth of perovskite films, resulting in uniform films and reduced defect states.