Enhancing Performance and Stability of Tin Halide Perovskite Light Emitting Diodes via Coordination Engineering of Lewis Acid–Base Adducts

For resolving toxicity issues of Pb-based perovskites, Sn-based perovskites have been widely studied as a promising alternative due to similar valence electron configuration between Sn²⁺ and Pb²⁺. However, desired Sn²⁺ in the precursor solution and film is easily oxidized to Sn⁴⁺, causing detrimental Sn vacancies and impurities in the films. Unfortunately, dimethyl sulfoxide, a ubiquitously used Lewis base for the fabrication of high-quality perovskite thin films via the adduct approach, further accelerates the oxidation of Sn²⁺ in the precursor solution. Herein, N,N′-dimethylpropyleneurea (DMPU) is proposed as an alternative Lewis base for the fabrication of high-quality Sn-based perovskite thin films. The strongly coordinating Lewis base DMPU is shown to suppress the oxidation of Sn²⁺ in the precursor solution while promoting growth of uniform and highly crystalline thin films. The PEA₂SnI₄ perovskite light emitting diode (PeLED) based on DMPU demonstrates dramatically improves luminance (L): a more than sixfold enhanced external quantum efficiency (EQE) and better operational stability than those of the device fabricated without DMPU. The optimum PeLED based on DMPU achieves a maximum L and EQE of 68.84 cd m⁻² and 0.361%, respectively. This study provides an important methodological base for studying Sn perovskites for development of high-performance and eco-friendly PeLEDs.