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

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.