Enhanced photoluminescence of CsPbBr3@Ag hybrid perovskite quantum dots

CsPbBr3@Ag hybrid nanocrystals are synthesized for the first time by reacting CsPbBr3 nanocrystals with AgX (X = Cl, Br, or I) powders in hexane. The morphologies of the hybrid nanocrystals showed that 2-5 nm Ag nanoparticles were nucleated randomly outside the CsPbBr3 nanocrystals, which indicated that Ag+ ions released by AgX powders could be reduced to Ag-0 by surfactant ligands of CsPbBr3 nanocrystals and aggregated to Ag nanoparticles. Significant enhancement of the photoluminescence intensity of CsPbBr3@Ag hybrid nanocrystals was observed compared with that of pure CsPbBr3 nanocrystals under the excitation of 400 nm light, which was mainly attributed to the enhanced absorbance of ultraviolet or blue light by the Ag induced plasmonic near-field effect. Numerical simulations showed that CsPbBr3@Ag hybrid nanocrystals provided intense local field amplification at the perimeter of Ag nanoparticles. However, Ag adhesion can also cause the deteriorating surface quality of CsPbBr3 nanocrystals, and in turn reduce photoluminescence quantum yield. Therefore, Ag adhesion has two completely different influences on the photoluminescence of hybrid perovskite quantum dots. To achieve an enhanced photoluminescence, we have to optimize CsPbClxBr(3-x)@Ag hybrid nanocrystals so that the effect of plasmonic resonance enhancement occupied a significantly advantageous position. The surface trap states served as a nonradiative relaxation pathway for the photogenerated charge carriers and decreased the emission quantum yield of the hybrid nanocrystals. This suggests that a potential issue concerning the performance of CsPbBr3@Ag hybrid nanocrystals was a trade-off between enhanced light absorbance of CsPbBr3@Ag hybrid nanocrystals and reduced photoluminescence due to energy transfer from CsPbBr3 nanocrystals to Ag nanoparticles. This simple method to construct CsPbBr3@Ag hybrid nanocrystals offers new opportunities to enhance optical properties and expand the application of perovskite quantum dots for light emitting diodes and other optoelectronic devices.