Broadband Cr^3+-sensitized upconversion luminescence in La_3Ga_5GeO_14: Cr^3+,Yb^3+,Er^3+

Abstract

Broadband-light-sensitized upconversion (UC) photon management phenomenon in La3Ga5GeO14:Cr3+,Yb3+,Er3+ is reported, featuring the concentrated broadband noncoherent light excitable at room temperature. Energy transfer among Cr3+/Yb3+/Er3+ in the Stokes and UC luminescence processes reveals that Yb3+ as a “bridge” is requisite for Cr3+-sensitized UC luminescence of Er3+. Low Cr3+ contents are preferred for UC luminescence of Yb3+-Er3+, since it would be quenched by high Cr3+ contents. The designed UC emissions 2H11/2→4I15/2 and 4S3/2→4I15/2 of Er3+ at around 510 ~560 nm are proposed to through Energy transfer upconversion (ETU) mechanism based on the Cr3+-Yb3+ dimer model with superexchange interaction according to crystallographic data and the decay curves of Er3+ UC emission. This research may open up a new perspective to design novel photonic materials excitable by broadband noncoherent light for improving the photoresponse of solar cells.