Efficient Pure-Red Tin-Based Perovskite Light-Emitting Diodes Enabled by Multifunctional Lewis-Base Additives

Tin-halide perovskites (THPs) offer a promising alternative to lead-halide perovskites (LHPs), addressing environmental concerns while providing excellent optoelectronic properties. However, the performance of THP light-emitting diodes (LEDs) remains inferior to their lead-halide counterparts due to challenges such as Sn 2 ⁺ oxidation, rapid crystallization, and high defect densities. Here, for the first time, a multifunctional Lewis-base reducing ligand triphenylphosphine (TPP) is reported, which simultaneously suppresses Sn 2+ oxidation and passivates defects in 2D THPs TEA 2 SnI 4 (TEA represents 2-thienylethylamine). The P atom in TPP, with its lone pair electrons on the 3p orbital, has low electronegativity and high electron density, which can effectively suppress Sn 2+ oxidation. Furthermore, σ-donation and π-conjugation effects from the three phenyl groups in the TPP molecule enable it to strongly coordinate with Sn 2+ , which passivates defects in TEA 2 SnI 4 . These properties enhance the stability and optoelectronic properties of THPs. When the optimized THP films are implemented as active layers in LEDs, they exhibit a narrow electroluminescence full-width at half-maximum of 28 nm, Commission Internationale de l'Eclairage x-coordinate exceeding 0.7, and a peak external quantum efficiency of 10.12%, sevenfold higher than the pristine devices. This work demonstrates the potential of molecular additives to enhance the device performance of tin-based perovskites.