Determination of vis and NIR quantum yields of Nd3+-activated garnets sensitized by Ce3+

One of the most important quantities to describe the efficiency of luminescent materials is the external photoluminescence quantum yield (ePLQY) which is defined as the ratio of emitted to absorbed photons and thus describes the conversion efficiency of a given phosphor. In optical spectroscopy two methods of determination are applied: The absolute measurement conducted in an integrating sphere and a relative measurement based on a reference material with a known quantum yield. So far both methods are only described for phosphors in the UV and visible range of the electromagnetic spectrum. By using Nd3+ sensitized and Ce3+ activated garnets with the general formula (Y,Lu)3Al5O12:Ce3+,Nd3+ ((Y,Lu)AG:Ce,Nd) we developed a method for the determination of the quantum yield in the near-infrared region. Therefore samples of different compositions have been synthesized and spectroscopically characterized. Starting point of the determination of the overall quantum yield is the determination of the quantum yield of the Ce3+ emission in the visible range by well-established methods. For using the proportionality of emission integral to the quantum yield it is necessary to scale and combine the measured spectra (460-1000 nm on the vis detector, and 900-1500 nm on the NIR detector). Furthermore, the accuracy of the method was evaluated not only by statistic calculations comprising the propagation of uncertainty but also by using branching ratio data of Nd3+ given in literature to check the generated overall emission spectra.