Unusually enhancing high-order photon avalanche upconversion of layered BiOCl:Er3+ semiconductor poly-crystals via Li+ ion intercalation doping

Highlights: • Photon avalanche upconversion of BiOCl:Er³⁺ poly-crystals increases greatly by doping Li⁺ ions. • Upconversion enhancement is due to increasing excitation field. • Intercalation doping of Li⁺ in layered BiOCl crystals improves its internal electric field. • Excitation field of Er³⁺ ions increases due to enhanced internal electric field. Efficient upconversion (UC) enhancement of lanthanide doped phosphors is highly desirable due to great application, but it might face severe challenges, especially for poly-crystal materials due to having relatively fewer defects and with less flexibility in material design. Here we present BiOCl semiconductor poly-crystals with two-dimensional structure, in which approximate 100-fold UC luminescence enhancement of Er³⁺ ion dopants can be readily achieved via intercalation doping of Li⁺ ions. As Li⁺ ions were incorporated into the interlayer of BiOCl crystals, unique internal electric field (IEF) in BiOCl that trigger unusual photon avalanche (PA) UC phenomena accompanying with excitation field enhancement of Er³⁺ ions can be improved significantly, leading to the excellent UC enhancement. These results may pave a novel way for constructing greatly efficient UC poly-crystal materials as well as enable an improved understanding for material structure to design efficient photonic materials.