Luminescence of hydrothermally fabricated PbF2:Er3+ particles and their application in bifacial silicon solar cells

We report the synthesis of PbF2:Er3+ particles using a hydrothermal method. The structure and upconversion emission properties of the products are investigated by scanning electron microscopy, X-ray diffractometer, Raman spectrophotometer and fluorescence spectrometry. An increase in Er3+ concentration in the crystals changes the PbF2 structure from a mixed phase to a cubic phase and decreases the grain size to nanoscale levels. Enhanced upconversion efficiency is achieved after annealing resulted from the formation of the cubic phase and the increase of grain size. The optimal Er3+ concentration is found to be 4% after annealing, and applied to the back of a bifacial silicon solar cell, maximum external quantum efficiencies of 0.38% and 0.79% are respectively obtained under 0.77 W/cm2 laser excitation (1560 nm) and AM1.5 + laser co-excitation.