Neutral inorganic salt additives universally regulate multicolor perovskites for efficient electroluminescence

Abstract

Quasi-two-dimensional (quasi-2D) perovskites show great potential in light-emitting diodes. The use of additives plays a key role in the passivation of defects and the suppression of low-dimensional phases. However, the effects of additives vary greatly in different perovskite formulations/films with different light-emitting bands. In this paper, the universal utility of additives was achieved through sodium hexafluorophosphate (NaPF₆). Benefitting from the neutral environment of the additives and the hydrogen bonds formed by PF₆⁻/PEA⁺ (F⋯H–N), the low-dimensional phases are effectively reduced, and the distribution of the medium/high-dimensional phases is more balanced. Meanwhile, the PF₆⁻ anionic group can passivate the uncoordinated Pb²⁺, and reduce the defect density of the film. Finally, a maximum EQE of 16.8% was achieved in quasi-2D PEA₂Cs_n−1Pb_nBr_3n+1 green PeLEDs (514 nm), which was significantly higher than that of the pristine device (a maximum EQE of 10%). Correspondingly, the maximum EQE of sky blue PeLEDs (490 nm) based on the mixed halogen [(PEA)_0.75(GA)_0.25]₂CsPb₂X₇ (X = Br and Cl) component can be increased from 5.6% to 9.6%. The maximum EQE of pure blue PeLEDs (474 nm) can be increased from 3% to 4%. This class of neutral additives provides a solution for high-performance quasi-2D perovskite electroluminescence.