Investigation of optical stability issues with embedded semiconductor quantum dots used as colour conversion material in LED lighting applications

In order to further improve the efficiency and the spectral quality of white-light LEDs new colour conversion materials which allow a selective and narrow banded conversion of the blue excitation light are needed. Quantum dots could be promising in this regard as they exhibit exactly these properties. For commercially used light sources a stable colour distribution has to be ensured over the entire lifetime. Our experiments revealed a very different degradation characteristic of phosphor and quantum dots. In this paper we present the results of different experiments which aim on the understanding of the mechanism for optical stability. We focused mainly on two degradation effects, a decrease of the photoluminescence intensity and a shift of the emission peak wavelength towards the blue.