Ligand-mediated evolution from CsPbBr3 to Cs4PbBr6/CsPbBr3 perovskite composites with intense green emission

Herein, CsPbBr(3 )and Cs4PbBr6/CsPbBr3 perovskite composites have been synthesized by a simple supersaturated recrystallization procedure. X-ray diffraction and absorption spectra confirm the evolution from CsPbBr3 to Cs4PbBr6 by adding oleic acid and oleylamine simultaneously, which leads to the formation of green emissive Cs4PbBr6/CsPbBr3 perovskite composites. Gaussian fitting of the emission spectra and luminescent lifetime investigation indicate that the green emission is attributed to both Cs4PbBr6 and CsPbBr3, which originates from the exciton radiative recombination mediated by the trap states and the electron-hole recombination, respectively. Moreover, the emissive Cs4PbBr(6) can further promote the emission of CsPbBr3 by energy transfer process in Cs4PbBr6/CsPbBr3 composites. The photoluminescence intensity declines by less than 10 % after 60 days of storage in ambient environment, reflecting the excellent stability of the composites for lighting and displaying application.