Absolute quantum yields in NaYF4:Er,Yb upconverters - synthesis temperature and power dependenceElectronic supplementary information (ESI) available: Experimental details: material synthesis and quantum yield measurements, FTIR Spectroscopy. See DOI: 10.1039/c2jm33457g

We investigate the temperature and power dependence of the emission quantum yield of NaYF 4 :Er,Yb upconverters. We show that the quantum yields may vary by almost three orders of magnitude. We demonstrate that formation of the hexagonal phase of this material is not in itself sufficient to guarantee high upconversion efficiency. We investigate the temperature and power dependence of the emission quantum yield of NaYF 4 :Er,Yb upconverters. We demonstrate that formation of the hexagonal phase of this material is not in itself sufficient to guarantee high upconversion efficiency