Ultraviolet to infrared downshifting in Ce and Yb co-doped aluminum oxynitride thin films

Abstract

We report for the first time on ultraviolet (UV) to near infrared (NIR) downshifting between cerium, Ce, and ytterbium, Yb, in aluminum oxynitride, Al(O)N, thin films prepared by the reactive magnetron sputtering technique. The crystal structure of the prepared samples has been investigated by x-ray diffraction and transmission electron microscopy. In addition, the content of Ce and Yb were determined by Rutherford backscattering spectrometry. The role of Ce in downshifting the absorbed excitation UV photons into NIR ones is supported by photoluminescence (PL) and PL excitation measurements of (Ce, Yb) co-doped samples. Time-resolved PL along with PL power-dependent measurements propose that a one-to-one photon mechanism is achieved through charge transfer state mediation. The present findings contribute to the racetrack of down-conversion (DC) solar cell topic by investigating such a DC phenomenon in a new matrix, Al(O)N.