Interface‐Directed Growth of Tin Perovskite for Efficient Light‐Emitting Diodes

Abstract Controlling the crystallization dynamics of solution‐processed tin perovskites remains pivotal yet challenging for achieving high‐performance lead‐free optoelectronic devices. Herein, it is demonstrated that substrate‐regulated interfacial nucleation governs crystal growth orientation and film quality of tin perovskites. The results show that pristine PEDOT:PSS substrates induce bottom‐interface‐dominated nucleation via strong PEDOT + ‐[SnI 3 ] n n− interactions, driving rapid upward crystallization of tin perovskites and yielding rough films with low photoluminescence quantum efficiency (PLQE: ≈26%). Strategic substrate modification with potassium citrate (PC) weakens the PEDOT + ‐[SnI 3 ] n n− interactions, thereby redirecting nucleation initiation to the top interface during solvent evaporation. This results in controlled downward crystallization of tin perovskites, forming smooth films with improved crystallinity and superior optoelectronic properties (PLQE: ≈41%). The optimized tin perovskite light‐emitting diodes (LEDs) achieve record‐breaking performance with an external quantum efficiency of 12.8% and a maximum radiance of 190 W sr −1 m −2 , which is the highest performance reported for tin perovskite near‐infrared LEDs to date. This work demonstrates interface‐directed crystallization control as an effective strategy for achieving high‐performance tin perovskite optoelectronic devices.