• upconversion;
  • Er3+ luminescence;
  • nano-scaled glass-ceramics;
  • water splitting

Visible-to-UV/violet upconversion luminescence is found and studied in oxyfluoride glass ceramics with Er3+ dopant concentrations of 3.5, 6.0, or 12.0 mol%, covering a broad pump-power range. The glass ceramics with doping levels of 3.5 and 6.0 mol% show the strongest upconversion luminescence intensity when compared to both higher doping levels and the respective precursor glasses. A comprehensive analysis of the involved upconversion mechanisms is presented. These materials could be useful to enhance the efficiency of the water-splitting systems by using UV/violet light upconverted from the green and red parts of the solar spectrum, which are an alternative to photovoltaic solar cells.