Intense 974 nm emission from ErxYb2−xSi2O7 films through efficient energy transfer up-conversion from Er3+ to Yb3+ for Si solar cell

► Using Er3+ as sensitizer, Yb3+ as activator in ErxYb2−xSi2O7 thin films. ► Intense 974 nm emission via UC process at Er3+4I13/2 level is obtained. ► Energy transfer up-conversion process is the dominant transition at Er3+4I13/2 level.