Interfacial Synthesis of Monodisperse CsPbBr3 Nanorods with Tunable Aspect Ratio and Clean Surface for Efficient Light-Emitting Diode Applications

To improve the efficiency of CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) based light-emitting diodes (LEDs), several parameters should be taken into consideration, including outstanding photophysical properties, efficient charge injection/transporting properties, and suitable device structure. In traditional synthesis of CsPbX3 nanocrystals, oleic acid and oleylamine are widely used as ligands, which require a complicated cleaning step to remove extra residual insulating ligands. In this work, monodisperse CsPbBr3 nanorods with tunable aspect ratio and a clean surface have been prepared through an interfacial conversion from Cs4PbBr6 nanocrystals. The formation process has been carefully investigated. The nanorods showed excellent photophysical properties, including a photoluminescence quantum yield up to 87% and a photoluminescence lifetime of 44 ns. According to the ultraviolet photoelectron spectroscopy measurement, CsPbBr3 nanorods show a higher valence band maximum than that of nanocubes, suggesting a more efficient hole injection rate that is favorable for LED applications. A prototype LED has been fabricated by using CsPbBr3 nanorods as green light source. Without any tedious cleaning step, the external quantum efficiency of the LEDs is over 8.2%, which is one of the best performances of CsPbBr3 NCs-based LEDs so far. This work not only provides a great candidate for high-performance LEDs but also sheds some light on the materials synthesis and device design.