Mitigating self-doping effect enables efficient tin-based perovskite light-emitting diodes

Tin (Sn)-based perovskites are promising eco-friendly candidates for next-generation displays, owing to their excellent optoelectronic properties and low-cost solution processability. However, the performance of Sn-based perovskite light-emitting diodes (PeLEDs) is hindered by uncontrolled crystallization and facile Sn2+ oxidation, leading to poor film morphology and high defect density. Herein, we propose a multifunctional hydroxyurea (HU) buried interface to regulate the crystallization kinetics and optoelectronic properties of Sn-based perovskites. The hydrophilic NH2 groups of HU establish a hydrogen-bond network with the perovskite halide ions, which enhances precursor wettability and increases the initial nucleation density to facilitate the growth of uniform, dense, and pinhole-free perovskite films. Furthermore, the C=O groups of HU can coordinate with uncoordinated Sn ions and effectively inhibit their oxidation. Moreover, the suppression of Sn2+ oxidation helps mitigate the Sn4+-induced self-doping effect, thus upshifting the valence-band maximum and reducing the hole injection barrier. Consequently, the optimized PeLED exhibits pure-red emission (620 nm) and achieves a maximum external quantum efficiency of 12.8%.