Photoluminescence Properties of Europium and Cerium Co-Doped Tantalum-Oxide Thin Films Prepared Using Co-Sputtering Method

We fabricated europium and cerium co-doped tantalum (V) oxide (Ta2O5: Eu, Ce) thin films using our co-sputtering method for the first time, and evaluated photoluminescence (PL) properties of the films after annealing at 600°C - 1100°C for 20 min. Four remarkable PL peaks at wavelengths of 600, 620, 700, and 705 nm were observed from the film annealed at 900°C. The intensities of the 700- and 705-nm peaks due to the 5D0 → 7F4 transition of Eu3+ were much stronger than those of the 600-nm (5D0 → 7F1) and 620-nm (5D0 → 7F2) peaks of the film annealed at 900°C. It seems that energy transfer from Ce3+ to Eu3+ occurs in the film, and much energy is selectively used for the 5D0 →7F4 and 5D0 → 7F1 transitions. Such a Ta2O5: Eu, Ce co-sputtered thin film seems to be used as a multi-functional coating film having both anti-reflection and down-conversion effects for realizing a high-efficiency silicon solar cell.