Researchers at Nanjing Tech University have made progress in achieving high-efficiency LEDs through the interfacially oriented growth of tin-based perovskites

Due to their non-toxicity and excellent optoelectronic properties, tin perovskites have emerged as promising alternatives to lead halide perovskites for optoelectronic applications, such as light-emitting diodes. However, tin-based perovskite devices often face challenges with uncontrolled nucleation and growth during thin-film formation. This uncontrolled crystallization often leads to films with high trap densities, which exacerbate nonradiative recombination and limit photoluminescence (PL) and electroluminescence (EL) efficiencies. Therefore, achieving precise control over crystallization is crucial to unlocking the full potential of tin perovskites in optoelectronic devices.

To address these challenges, various strategies, such as size engineering, solvent vapor engineering, additive engineering, and interface engineering, have been explored to modulate the crystallization of tin perovskites. Notably, recent studies have demonstrated significant differences in the morphology of tin perovskite films deposited from similar precursor solutions on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and indium tin oxide (ITO) substrates. These findings highlight the critical role of substrate properties in controlling the crystallization of tin perovskites. While previous studies primarily attributed the effects of PEDOT:PSS to its unfavorable acidity, the specific mechanisms by which substrates influence nucleation and growth remain poorly understood.

Wang Jianpu, Huang Wei, Chang Jin, et al. from Nanjing Tech University demonstrate that pristine PEDOT:PSS substrates induce bottom-interface-dominated nucleation through strong PEDOT+-[SnI3]nn- interactions, driving rapid upward crystallization of the tin perovskite and producing rough films with low photoluminescence quantum efficiency (PLQE: ≈26%). Strategic modification of the substrate with potassium citrate (PC) weakens the PEDOT+-[SnI3]nn- interactions, thereby shifting the nucleation initiation to the top interface during solvent evaporation. This results in controlled downward crystallization of the tin perovskite, forming smooth films with enhanced crystallinity and superior optoelectronic properties (PLQE: ≈41%). The optimized tin perovskite light-emitting diode (LED) achieved record-breaking performance, with an external quantum efficiency of 12.8% and a maximum luminance of 190 W sr?? m??, the highest performance to date for tin perovskite near-infrared LEDs. This work demonstrates that interface-directed crystallization control is an effective strategy for achieving high-performance tin perovskite optoelectronic devices.