Stabilizing FASnI 3 -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 3 ) 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 3 -based perovskite LEDs (PeLEDs) show limited stability, with T 50 lifetimes of up to 0.25 h at 10 mA cm -2 . Here, we improve the stability of FASnI 3 -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 2+ to Sn 4+ . 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 -1 m -2 , and a record-long T 50 lifetime of 10.3 h at 100 mA cm -2 for FASnI 3 -based PeLEDs. Our results illuminate an alternative path toward lead-free PeLED applications.