Smoothing Energy Transfer Enabling Efficient Large‐Area Quasi‐2D Perovskite Light‐Emitting Diodes

Abstract Electroluminescence (EL) efficiency of perovskite light‐emitting diodes (PeLEDs) based on a few square millimeters has improved significantly in recent years. Nevertheless, the EL efficiency of PeLEDs would plunge once the active area is enlarged from a millimeter to even a subcentimeter due to the unsmooth energy transfer process among the edge region with numerous nonradiative recombination centers. Herein, an intriguing strategy is developed to realize high‐quality quasi‐2D perovskite thin film via tuning perovskite precursor rheological properties as well as modulating the substrate surface tension. The perovskite crystallization process is retarded by incorporating a strong chelating ligand into its precursor. Hydroxylamine‐O‐sulfonic acid, containing a sulfonic acid group and an amino group, acts as a strong chelating agent with lead ions (Pb 2+ ), which exhibit great synergistic potential in defect passivation and crystallization modulation. As a result, a large‐area (25 cm 2 ) quasi‐2D PeLED achieves an external quantum efficiency of 20.7% with uniform emitting characteristics, a record value among analogous same‐size PeLEDs. The work may pave the way to realize high‐performance large‐area perovskite optoelectronic devices.