Phase Aggregation Suppression of Homogeneous Perovskites Processed in Ambient Condition toward Efficient Light‐Emitting Diodes

Perovskite light‐emitting diodes (PeLEDs) have attracted attention because of their high efficiencies. However, due to the sensitivity of perovskites to ambient condition, perovskite emitter layers are generally fabricated under an inert gas environment (e.g., dry N2), which increases processing complexity and cost. Here, air‐prepared quasi‐2D perovskites are reported for efficient PeLEDs. It is found that the phase aggregation is the major obstacle deteriorating the characteristics of air‐prepared perovskites. Through antisolvent engineering to modulate the nucleation and growth characteristics of perovskite films from precursor solution, phase aggregations are restrained. Confocal laser scanning fluorescence microscopy results demonstrate homogeneous perovskite films with uniform photoluminescence distributions. Traps at grain boundaries are passivated, and exciton transfer among perovskite phases becomes effective. Finally, efficient green PeLEDs based on air‐prepared perovskites are realized with an external quantum efficiency of 15.4%. This work provides a promising strategy to fabricate cost‐effective perovskite devices in ambient air condition. Air‐prepared homogeneous quasi‐2D perovskites are formed through suppressing the adverse phase aggregation. Exciton transfer among different perovskite phases becomes effective and an external quantum efficiency of 15.4% is realized in green perovskite light‐emitting diodes.