Optical and structural properties of down-conversion Bi doped Y2O3 films for potential application in solar cell

The highly efficient antireflective down-conversion Bi-doped Y2O3 films have been deposited on the (100) oriented Si and quartz substrates by rf reactive magnetron sputtering using a metallic target. The effects of the Bi doping concentration on the optical and structural properties of the films were studied. The Bi/Y ratio in the films varied from 0.002 to 0.02. The undoped Y2O3 films show a cubic phase crystal structure with a preferred orientation along the (222) direction. Bi doping results in the appearance of the (111) oriented monoclinic phase crystal structure. The refractive index is increased and the optical band gap is decreased as the Bi concentration in the films is increased. The bright green photoluminescence of Bi ions was observed under ultraviolet light excitation for all the Bi-doped Y2O3 films and the luminescence intensity increases as the Bi/Y ratio is increased from 0.002 to 0.02. In addition, Bi-doped Y2O3 films show a much lower optical reflectance than the undoped Y2O3 films. These results make the Bi-doped Y2O3 films a potential application not only as a spectrum converting layer but also as an antireflective layer in crystalline Si solar cells.