Synergistic Crystallization Regulation and Defect Passivation via Dual Additives for High-Efficiency Quasi-2D Perovskite Light-Emitting Diodes

Quasi-2D perovskites have garnered significant attention for their light-emitting diode (LEDs) applications but suffer from nonuniform distribution across multiple phases. This property hampers energy transfer and creates abundant grain boundaries and surfaces. These structural flaws become hotspots for defect-assisted recombination, severely limiting the device performance. In this study, we report a strategy to synergistically passivate defects and tune the crystallization of quasi-2D perovskites via dual additives of guanidine bromide (GABr) and piperazine hydrobromide (PBr). The GA + and R 2 NH groups, which are provided by GABr and PBr, respectively, can effectively passivate the uncoordinated Pb 2+ defects. Furthermore, the hydrogen-bonding interactions between R 2 NH 2 + and [PbBr 6 ] 4– modulate the crystal growth process, transforming the multi- n phase distribution into a concentrated distribution of high- n phases, thereby enhancing device performance. As a result, the resulting green BA 2 Cs n –1 Pb n Br 3 n +1 PeLED exhibits a current efficiency of 53.05 cd/A and a peak external quantum efficiency of 15.68% at an emission wavelength of 512 nm, which is significantly higher than that of the control device. This study offers an innovative approach for strategically manipulating the phase distribution within quasi-2D perovskite films and significantly diminishing defect density, thereby paving the way for the development of high-efficiency PeLEDs.