Rare Earth Ion‐Doped Metal Halide Perovskite Miro‐Nano Single Crystals for Low Threshold Perovskite Lasers

Abstract Metal halide perovskites (MHP) have emerged as promising candidates for optoelectronic devices, particularly lasers. Nevertheless, achieving a low pumping threshold remains a critical bottleneck for practical laser applications. Here, a rare‐earth ion doping strategy to address this challenge based on CsPbBr 3 single crystals microribbons (SCMRs) or microwires (SCMWs), achieving a low threshold from undoped counterparts is proposed. First, through optimized Ce 3+ doping control, the introduction of 5 mol% Ce 3+ in the precursor solution (with an actual doping concentration of 0.57 mol% Ce 3+ ) reduced the lasing threshold of CsPbBr 3 : Ce 3+ single‐crystal microribbons from 10.7 to 5.1 µJ cm 2 . Building upon 5% Ce 3+ as the optimal doping concentration, Er co‐doping further lowered the threshold to 1.5 µJ cm 2 in SCMWs of identical dimensions, the threshold is further reduced from 1.9 to 1.5 µJ cm 2 . Mechanistic studies reveal synergistic effects: 1) surface defect passivation minimizing non‐radiative losses, 2) intermediate energy levels enabling efficient exciton recombination, and 3) Förster resonance energy transfer (FRET) between Ce 3 ⁺→Er 3 ⁺. This approach demonstrates universality in chloride/bromide MHPs but fails in iodides due to bandgap mismatch with rare‐earth energy levels. This work provides a feasible route to improve efficiency in MHP lasers for integrated photonic circuits.