Lead halide perovskite quantum dots (QDs), a shining star in the world of new semiconductor materials, rely on their excellent photoluminescence quantum yield (PLQY), excellent color purity, wide color gamut adjustment ability and excellent solution Processability is shining in the field of thin film optoelectronic devices. In the research and application of perovskite QDs, surface ligands play a crucial role in the PLQY, stability and carrier transport properties of QDs.

Therefore, in the process of developing high-performance perovskite QDs and preparing efficient quantum dot light-emitting diodes (QLEDs), rational selection and matching of surface ligands is particularly critical. Since perovskite QDs have a large specific surface area, the presence of surface defects will significantly affect the optical properties of perovskite QDs. Therefore, it is usually necessary to use an excess of organic ligands to effectively passivate QDs surface defects. However, the insulating nature of organic ligands will severely limit the carrier injection and transmission efficiency of perovskite QDs in subsequent optoelectronic devices.

In response to the above problems, based on the early use of multifunctional short-chain thiophene alkyl ammonium bromide ligands to improve the performance of perovskite quantum dot light-emitting diode devices (ACS Applied Materials & Interfaces2023, 15(33), 40080-40087), Wu Chaoxin The professor's team took advantage of the advantages of conjugated organic ligands, including their delocalized seals. (E)-3-(4-substituted phenyl)propyl-2-en-1-amine hydrobromide derivatives (PPABr, 4-CH3PPABr and 4-F PPABr) and used it as a post-exchange ligand to regulate carrier injection and transport of perovskite QDs.

Combining theoretical calculations and experimental studies, it was found that this type of conjugated ligand has a more dispersed electron cloud distribution along the entire molecular skeleton, and its introduction into CsPbBr3QDs can significantly improve the carrier transport of perovskite QDs films. Among them, 4-CH3PPABr with electron-donating substituents effectively promotes hole transport, while 4-F PPABr with electron-withdrawing substituents is more conducive to electron transport.

Finally, the optimal green QLED based on 4-CH3PPABr achieved a maximum external quantum efficiency (EQE) of 18.67%. By combining a high-refractive index substrate and a high-refractive index lens, its maximum EQE is further increased to 23.88%. This work provides a new idea for achieving balanced carrier transport in QLEDs through ligand design.