Strong 1550 nm to visible luminescence in In/Er/Yb:LiNbO3 crystal considered as an upconverter for solar cells

Abstract

Enhanced green and red upconversion emissions are observed in Er/Yb:LiNbO₃ codoped with 3 mol% In³⁺ ions under both 1550 nm and 980 nm excitation, which provides more probabilities to increase efficiently the solar spectrum response and further increase the photovoltaic efficiency of solar cells. The energy transfer (ET: ²F_7/2 Yb + ⁴I_11/2 Er → ²F_5/2 Yb + ⁴I_15/2 Er) and the energy back transfer (EBT: ²F_5/2 Yb + ⁴I_13/2 Er → ²F_7/2 Yb + ⁴F_9/2 Er) processes are also responsible for the population of the red emitting ⁴F_9/2 state (Er) under 1550 nm excitation. The increased red emission is attributed to the dissociation of Er³⁺ cluster sites in the In/Er/Yb:LiNbO₃ crystal.