Locking Energy Transfer of Rare Earth Ions via an Electron Jam Caused by Vertical Photocarrier Separation of a Layered Semiconductor

Energy transfer (ET) of trivalent rare earth (RE)-doped inorganic crystals has been investigated comprehensively from theory to technology; however, the influence of photocarrier transmission has been considered impossible, as the 4f electrons of RE ions are shielded well from outer electrons. Here, on the basis of an anisotropic Bi3O4Cl layered semiconductor, we report for the first time the ET phenomenon of an Er3+-Yb3+ codoped system locked by photocarrier separation. When the photocarrier of the layered host is separated efficiently under a vertical spontaneous interelectric field, the ET and energy-back-transfer (EBT) between Er3+ and Yb3+ ions can be inhibited completely; otherwise, they can occur as usual. Consequently, the Yb3+ ion dopant mainly acts as a quencher for 980 nm-excited visible upconversion (UC) and infrared emission of Er3+ ions, and the cross-relaxation between Er3+ and Yb3+ ions via EBT is inhibited simultaneously. We show that the separated photoholes on the surface can suppress the recombination of excited electrons of Er3+ ions to the ground level, leading to a special electron jam on intermediate levels, which prevents the acceptance of excited electrons further via either the ET or EBT process. The result of our current work greatly enhances the understanding of ET behavior of RE ions and the material structure of RE-doped materials.

Automated summary

This study investigates the influence of photocarrier transmission on the energy transfer of trivalent rare earth-doped inorganic crystals. The researchers discovered that efficient separation of photocarriers can inhibit the energy transfer between Er3+ and Yb3+ ions, thereby suppressing infrared emission. Additionally, the separated photoholes block the recombination of excited electrons, preventing further energy transfer.