Zinc oxide is one of the most promising semiconductors for solar cell up-and downconverters because it's cheap and appropriate host for lanthanides . The lanthanides atoms on ZnO surface can effectively convert UV and visible light into near-infrared range where the c-Si solar cells strongly absorb light . The light conversion can occur through non-radiative energy transfer from excited state of ZnO to the excited states of lanthanide ions with subsequent light emission in the infrared range . The energy transfer is quite an effective process resulting in the efficiency of up to 200% when quantum cutting takes place .