Synthesis of Yb³⁺/Er³⁺ co-doped Y₂O₃, YOF and YF₃ UC phosphors and their application in solar cell for sub-bandgap photon harvesting

Yb³⁺/Er³⁺ co-doped Y₂O_3, YOF and YF₃ upconversion (UC) phosphors were synthesized by co-precipitation method. The three upconversion phosphor samples show strong green (540 nm) and red (660 nm) emission bands visible to naked eyes even at the low intense incident light. The potential application of Y₂O_3, YOF, and YF₃ UC phosphors was demonstrated by incorporating them in amorphous silicon thin film solar cells and they showed upconversion current densities of 0.36 mA/cm², 0.23 mA/cm², and 0.207 mA/cm² respectively when the cell was illuminated with a 980 nm IR laser. Intensity-dependent J-V studies were carried out to understand the effectiveness of UC phosphors in improving solar cell parameters. An improvement of 7.5% in J_sc was obtained for amorphous silicon solar cell incorporated with YF₃ UC phosphors under AM1.5 along with 980 nm NIR illumination.