Stabilizing FASnI-based perovskite light-emitting diodes with crystallization control.

The toxicity of lead presents a critical challenge for the application of perovskite optoelectronics. Lead-free perovskite solar cells were achieved with formamidinium tin iodide (FASnI) perovskites, exhibiting decent power-conversion efficiencies (PCEs) of up to 14%, with >98% of the initial PCE retained after 3000 h of storage. However, when employed in light-emitting applications, FASnI-based perovskite LEDs (PeLEDs) show limited stability, with lifetimes of up to 0.25 h at 10 mA cm. Here, we improve the stability of FASnI-based PeLEDs through the inclusion of a two-dimensional precursor phenethylamine iodide (PEAI), allowing controlled crystallization of the mixed-dimensional perovskite emitters. The density of defects is found to be reduced, accompanied by the suppression of oxidation from Sn to Sn. Using an optimized perovskite composition, we achieve an EQE of 1.5% (a ∼10-fold improvement over the control devices), a maximum radiance of 145 W sr m, and a record-long lifetime of 10.3 h at 100 mA cm for FASnI-based PeLEDs. Our results illuminate an alternative path toward lead-free PeLED applications.