Upconversion for enlarging solar spectrum response in near-stoichiometric and congruent Er:LiNbO3 crystals

- An enhancement of green upconversion emission is observed in Er:NSLN.
- The Er3+ cluster sites (ErLi2+-ErNb2-) are dissociated in Er:NSLN crystal.
- Enhanced green emission arises from the inefficient cross relaxation process.
- Er:NSLN will be considered as an upconverter to improve solar spectrum response.