High‐Efficiency Quasi‐2D Perovskite Light‐Emitting Diodes Using a Dual‐Additive Strategy Guided by Preferential Additive‐Precursor Interactions

Abstract Quasi‐2D perovskites are promising emitters in light‐emitting diodes (LEDs) due to their natural quantum well (QW) structure and tunable exciton binding energy. Synergistic regulation of the defect passivation and QW width distribution of quasi‐2D perovskites is crucial to achieve high‐performance perovskite‐based LEDs. Herein, a combination of two additives, i.e., 3‐(diaminomethylidene)‐1,1‐dimethylguanidine (Metformin) and 1,4,7,10,13,16‐hexaoxacyclooctadecane (Crown) having preferential interactions with different quasi‐2D perovskite precursors is proposed to synergistically passivate the defects and regulate the QW width distribution of quasi‐2D perovskites. Metformin additive interacts strongly with lead bromide, mainly passivating the defects. Crown additive has preferential interactions with organic spacer phenethylammonium bromide, which dominates the QW width distribution and induces quasi‐2D perovskites with uniform dimensions. The dual additives of Metformin and Crown interact preferentially with distinct precursors, allowing to regulate the QW width distribution and defect density of quasi‐2D perovskites synergistically. A photoluminescence quantum yield as high as 91.5% is achieved for the quasi‐2D perovskite prepared with the dual‐additive strategy. Moreover, high‐efficiency quasi‐2D perovskite LEDs were successfully fabricated with a maximum external quantum efficiency of 21.3% and a maximum luminance over 30 000 cd m⁻². This work provides a preferential interaction‐guided dual‐additive strategy to fabricate high‐efficiency quasi‐2D perovskite LEDs without anti‐solvent treatment.