An important factor in photocatalysis is the spectral overlap of the materials used with the solar emission spectrum. My research aims at improvement of the photocatalytic efficiency by combining photocatalysts with phosphors. I study the relationship between the catalytic activity, electron storage capacity and position of energy levels of phosphor/photocatalyst composites. Mechanisms and dynamics of energy and electron transfer between phosphor and photocatalyst are investigated by time-resolved spectroscopy. To this end, highly efficient and round-the-clock phosphor/photocatalyst composite materials will be designed.