Pre‐Nucleation Strategy for Room‐Temperature Growth of Perovskite Single Crystals toward Efficient Perovskite Light‐Emitting Diodes

Abstract Metal lead perovskite (MHP) single crystals (SCs) with extraordinary optical properties are promising candidates for high‐performance SC‐based perovskite light‐emitting diodes (SC‐PeLEDs). However, the heating process involved in traditional methods to initiate crystal nucleation and growth inevitably induces massive defects in MHP SCs, leading to inferior electroluminescence performance and poor operational stability of the SC‐PeLEDs. Preparation of low‐defect thin MHP SCs for high‐performance SC‐PeLEDs remains a formidable challenge. Here, a facile pre‐nucleation strategy is developed to enable room‐temperature (RT) growth of high‐quality MAPbBr 3 (MA + = CH 3 NH 3 + ) SCs. By avoiding the detrimental effect of high growth temperature, the MAPbBr 3 SCs prepared at RT show improved crystallinity with lower trap‐state density, giving rise to higher photoluminescence quantum yield and uniform fluorescence. Consequently, the MAPbBr 3 ‐based SC‐PeLEDs achieve a high external quantum efficiency up to 9.7%, along with an ultrahigh luminance of 126 800 cd m −2 , which is among the highest for MAPbBr 3 ‐based SC‐PeLEDs. Moreover, the SC‐PeLEDs demonstrate remarkably high operational stability with half‐lifetimes as long as 594 min and 33.2 min at initial luminances of ≈1000 cd m −2 and ≈10 000 cd m −2 , respectively. The work has excellent universality and paves the way toward the fabrication of high‐performance SC‐PeLEDs for future lighting, display, and laser applications.