Upconversion for enlarging solar spectrum response in near-stoichiometric and congruent Er∶LiNbO_3 crystals

摘要

To increase the photovoltaic efficiency of solar cell, the visible luminescence produced at the excitation of the near infrared laser light in near-stoichiometric and congruent LiNbO_3 crystals heavily doped with Er~(3+) ions (Er：NSLN and Er：CLN, respectively) were investigated. An enhancement of the green upconversion emission observed in Er：NSLN crystal was attributed to the inefficient cross relaxation processes of ~2H_(11/2) + ~4I_(13/2) → ~4I_(11/2) + ~4F_(9/2) and ~4F_(7/2) + ~4I_(11/2) → ~4F(9/2) + ~4F(9/2). The Er content in the crystal was measured by an inductively coupled plasma mass spectrometry (ICP-MS). The OH- absorption and UV-vis-near infrared absorption spectra indicated that the Er_(3+) cluster sites (Er~2_(Li) -Er~(2-)_(Nb)) were dissociated in Er：NSLN crystal. The strong green upconversion emission produced by Er：NSLN crystal will be beneficial for improving the practical performance of solar cells.