Highly stable hetero-structured supercell, green-emitting cesium lead bromide by ligand-mediated phase control
Green-emissive Cs4PbBr6 shows promise for light-emitting diode devices over CsPbBr3 NCs owing to their stable and high photoluminescence efficiency. Nevertheless, there is still no consensus regarding the basis of their green emission, which decelerates their advance in light-emitting applications. Herein, a systematic investigation on the concentration of capping ligands (oleylamine and oleic acid), which determines the predominant phase between CsPbBr3 and Cs4PbBr6 for a given Cs to Pb feed ratio is conducted. This study deduces that oleylamine to oleic acid ratio plays a crucial role in obtaining either green-emissive or non-emissive Cs4PbBr6 NCs. Scrutiny of Cs4PbBr6 microscopic and optical data in addition to their emission quenching study with a hole-withdrawing molecule reveals that the green emission originates from CsPbBr3 impurity phase. Furthermore, stable green emission is observed for CsPbBr3/Cs4PbBr6 nanocrystals when CsPbBr3 particles are well protected by Cs4PbBr6 matrix. These CsPbBr3/Cs4PbBr6 films remained highly luminescent even after UV exposure for hours or annealing at ~150oC for days in addition to their long-term stability in ambient atmosphere, which are desirable properties for various practical applications.
- This article is part of the themed collection: 2019 Nanoscale HOT Article Collection