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 PEA2Csn−1PbnBr3n+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.