Broadband downshifting luminescence in Cr³⁺₋Yb³⁺ codoped garnet for efficient photovoltaic generation

The Cr³⁺₋Yb³⁺ codoped YAG crystals were synthesized by the solid state reaction method, in which the intense near-infrared emission around 1000 nm originated from Yb³⁺ ²F₅/₂ →²F₇/₂ transition was obtained due to the efficient energy transfer from Cr³⁺ to Yb³⁺. The stable and transient spectral measurements revealed that the phonon assistant energy transfer process is responsible for the energy transfer from Cr³⁺ to Yb³⁺ upon both the excitations of Cr³⁺: ⁴T₁ and ⁴T₂> energy levels. Due to the effective absorption of Cr³⁺ in the visible region in YAG and the efficient energy transfer to Yb³⁺, this material can be developed as spectral convertors to improve silicon solar cell photovoltaic conversion efficiency.