  The new generation of laser-based solid-state lighting (SSL) white light
sources requires new material systems capable of withstanding, diffusing and
converting high intensity laser light. State-of-the-art systems use a blue
light emitting diode (LED) or laser diode (LD) in combination with color
conversion materials, such as yellow emitting Ce-doped phosphors or red and
green emitting quantum dots (QD), to produce white light. However, for
laser-based high-brightness illumination in particular, thermal management is a
major challenge, and in addition, a light diffuser is required to diffuse the
highly focused laser beam. Here, we present a hybrid material system that
simultaneously enables efficient, uniform light distribution and color
conversion of a blue LD, while ensuring good thermal management even at high
laser powers of up to 5W. A highly open porous (> 99%) framework structure of
hollow SiO$_2$ microtubes is utilized as an efficient light diffuser that can
drastically reduce speckle contrast. By further functionalizing the microtubes
with halide perovskite QDs (SiO$_2$@CsPbBr$_3$ as model system) color
conversion from UV to visible light is achieved. Under laser illumination, the
open porous structure prevents heat accumulation and thermal quenching of the
QDs. By depositing an ultrathin (~ 5.5 nm) film of poly(ethylene glycol
dimethyl acrylate) (pEGDMA) via initiated chemical vapor deposition (iCVD), the
luminescent stability of the QDs against moisture is enhanced. The demonstrated
hybrid material system paves the way for the design of advanced and functional
laser light diffusers and converters that can meet the challenges associated
with laser-based SSL applications.
