Figure 6.

Conceptual approaches for implementing extrinsic spectral conversion with natural and artificial photosynthesis. a) The design of a frontlight (left) and a backlight (right) photoluminescent converter and its application with a flat‐panel microalgae reactor.7 b) A typical phosphor material (here: (Ca,Sr)S:Eu²⁺ for green‐to‐red downshifting (top). This phosphor can be coated on a light‐guiding and light‐concentrating optical fiber—example shown here (middle): 0.5 mm in diameter, PMMA, front‐end (left) coated with (Ca,Sr)S:Eu²⁺—for tailored light delivery. Large‐area fabrics can be manufactured from such fibers (bottom, showing un‐coated fiber). c) Summary of an exemplary concept of seawater‐splitting, where the intense solar irradiance of the Canary Islands (top, in kWh m⁻² per day) and the existing infrastructure of salt‐flats (middle) are used as the basis for H₂ generation in shallow, covered ponds which comprise slurries of photoconverters and photocatalysts in a combination of back‐ and frontlight converters. Reproduced with permission.88 Copyright 2013, Royal Society of Chemistry.