Unusual photoluminescence regulation of single-crystalline BiOCl:Eu3+ nanosheet by C-heterovalent doping: The evidence of photoferroelectric effect on the transitions of the RE3+ optical activator

Substitutional heterovalent doping has been an effective method to manipulate the optical properties of Lanthanide-doped phosphors in the past. Herein, we report a new strategy of nonmetal atom carbon dopant in BiOCl nanosheets for tailoring the electric dipole transitions (EDTs) of Eu3+ ions, in which photoferroelectric effect (PFE) play a crucial role rather than the traditional lattice modification. Experimental results and first-principles calculations provide evidence that the replacement of C ions for CI gives rise to strengthen macroscopic polarization and spontaneous inter electric field (IEF) of BiOCl. Under interband excitation, the enhanced PFE triggered by the IEF generated higher photopolarzition field and carrier separation efficiency. Consequently, the intensity ratio of D-5(0)-F-7(4)/D-5(0) F-7(2) transition of Eu3+ ion was enhanced significantly due to environmental sensitivity of EDTs, accompanying with prolonged decaytimes. However, under intraband excitation where no PFE occurs, all of these factors exhibit the opposite tendency with the increase of C dopants. The result of our work shows that the tunable PFE via C-heterovalent doping in the layered BiOCl host offer a new method that utilize the light-matter interactions to modify the PL properties of rare-earth (RE) ion doped materials.