|Cyan, magenta, and yellow filters for liquid-crystal displays are photovoltaic, harvesting wasted energy. (Images: Jay Guo)|
Ann Arbor, MI--A new type of color filter for pixels in liquid-crystal displays (LCDs) has been developed by researchers at the University of Michigan: in addition to providing a pixel's hue, the filter is a photovoltaic cell that can harvest some of the wasted light from the display for useful energy.1 You may ask, Does this make sense? In fact, yes it does -- in a typical LCD less than 8% of the backlighting reaches the viewer's eyes, which is partially due to the absorbing color filters. Even a rudimentary energy-harvesting ability would help wall-plug efficiency.
The photovoltaic filter, developed by Jay Guo and his group, converts about 2% of the light that would otherwise be wasted to power. This could add up to a significant amount in small electronics, says Guo.
The researchers created the new filter by adding organic semiconductor photovoltaic cells to an ultrathin color filter, similar to what Guo's lab had created more than a year ago. That filter is composed of nano structured gratings that act as resonators for light of a particular color. The color depends on the grating period.
At 200 nm thick, the new filter is 100 times thinner than traditional colorant-based filters, a characteristic that could be attractive for use in future ultrathin color displays. The technology could also potentially be used in larger displays to make energy-harvesting billboards or decorative solar panels.
The University of Michigan is pursuing patent protection for the intellectual property.
1. Hui Joon Park et al., ACS Nano, 2011, 5 (9), p. 7055.