By substituting the phosphor screen in a laser phosphor display (LPD) with a luminescent solar concentrator (LSC), energy can be harvested from ambient light as well as display high-resolution images. "Energy-harvesting laser phosphor display and its design considerations," published recently by SPIE, the international society for optics and photonics, in the Journal of Photonics for Energy, illustrates the development, processes, and applications of an LPD.
In a proof-of-concept research, lead author Ichiro Fujieda and his colleagues at Ritsumeikan University built a 95 × 95 × 10 mm screen by sandwiching a thin layer of coumarin 6 between two transparent plates. These plates guided the photoluminescent (PL) photons discharged in both directions toward their edge surfaces. After taking out the light source in a DMD-based commercial grade projector and feeding a blue laser beam into its optics, the screen produced green images.
Attaching a photodiode with a 10 × 10 mm sensitive area on the bottom edge of the screen to record the power of the PL photons specified that a completely covered version would harvest up to 71% of the incoming optical power. However, a ghost image was visible when displaying a high-contrast still image.
The researchers address two features in their design considerations.
First, tiling small modules and removing the PL photons in each module decreases the thickness of a large-area system and eases the effect of self-absorption. For seamless tiling, fastening an output coupler to the wave guiding plate and mounting solar cells offers an optimal solution.
Second, the source of the ghost image is the PL photons reflecting at the interface between the rear plate and the outer environment. By decreasing the thickness of the rear plate on the LPD, they managed to remove this optical cross-talk between pixels.
Journal of Photonics for Energy associate editor Loucas Tsakalakos called the research "a unique and novel application of a luminescent solar concentrator for display applications. The work shows practical operation of such a device, describes the basic operational principle and expected energy harvesting capability of such a system, and describes ways of improving the design in future work."