Highly Stable O-Tolylbiguanide-CsPbI₃ Quantum Dots and Light-Emitting Diodes by Synergistic Supramolecular Passivation

Developing effective strategy to passivate surface defects in quantum dots (QDs) is critical to achieving high-efficiency and long-life perovskite light-emitting diodes (LEDs). Here, the supramolecular interaction underpinning of organic-inorganic components is exploited and a facile method is proposed to generate multiple-hydrogen-bonded supramolecular-perovskite crystal structures on QD surfaces by introducing O-Tolylbiguanide (O-Tg) during QD synthesis, enabling bright, conductive, and water-resistant CsPbI3 QDs. Compared with commonly used oleic acid and oleylamine ligands, the biguanide functional group in O-Tg not only forms multiple hydrogen bond interactions with lead halide octahedra passivating both bridging- and terminal-halogen ion defects, but also compatibly occupies the A-site position stabilizing the crystal structure simultaneously. With fewer nonradiative defects and introduced hydrophobic benzene rings preventing eroding of polar molecules, CsPbI3 QDs exhibit remarkable photoluminescence quantum yields of 96%, and their film can be submerged in water for 30 h without degrading. The corresponding LEDs display a high external quantum efficiency (21.2%) and offer superior operational stability with a lifetime (T-90) of 25 h at a constant current density as high as 50 mA cm(-2).