Production and Characterization of Tb³⁺/Yb³⁺ Co-Activated AlON Thin Films for Down Conversion Applications in Photovoltaic Cells

Terbium and ytterbium co-doped aluminum oxynitride thin films were grown onto silicon substrates using radiofrequency magnetron sputtering. Aluminum oxynitride samples doped with 4.6 at. % of Yb³⁺ and co-doped with 0.4 at. % of Tb³⁺ were obtained. The prepared samples were annealed from 150°C to 850°C in steps of 100°C. By using energy dispersive X-ray analysis we measured the sample composition and the doping concentration. The emission intensities at different annealing temperatures were characterized using photoluminescence measurements upon excitation at 325 nm. The ⁵D4 → ⁷F5 main transition of Tb³⁺ and the characteristic near infrared emission at 980 nm of Yb³⁺ were recorded. In order to study the luminescence behavior of the samples in terms of a down conversion process, we have plotted the integrated areas of the main transition peaks versus the annealing temperature.