New design gives screen displays bright color images even in sunlight

Viewing high-quality images with optimal colors, even when looking at a tablet or smartphone in direct sunlight, may be possible when new research results are commercialized.

A research team at the Chalmers University of Technology in Sweden has created a new design that solves the problems of low reflectance and limited colors when currently available screens are viewed in sunlight. 

Their work appears in the May 10 issue of Nano Letters.

The research advance not only produces brighter images, it also saves energy by using only a tenth of the energy currently used in light-emitting diodes or liquid crystal displays.

Researchers started with a new material that they previously developed – a porous inorganic nanostructure of tungsten trioxide (WO₃) with a thin layer of gold and a thin platinum mirror.

But their latest innovation inverts the traditional display design: The color reproduction is on top and the electrically conductive material underneath. 

Summarizing their advance, the researchers write:

"We show a new design for inorganic electrochromic nanostructures which circumvents the problem of low reflectance while still providing an excellent color range. This is achieved by selecting the right metals and reversing the thin film layers, enabling all electrical components to be 'hidden' behind the reflective surface."

The inverted design allows viewers to look directly onto the colors, instead of looking through the electrolyte and counter electrode, as in current screen displays.

The researchers tested different metals and different nanostructures (those measured in billionths of a meter) and found platinum to be the best back-reflector, with 20 nanometer gold the best nanohole layer. The high-cost metals – gold and platinum – are used in very thin layers for the reflective screens, so only minimal amounts are needed.

Another cost-saver in the design is energy use. Research leader Andreas Dahlin, professor in the Department of Chemistry and Chemical Engineering at Chalmers, stated in a press release:

"Our main goal when developing these reflective screens, or electronic paper, as it is sometimes termed, is to find sustainable, energy-saving solutions. And in this case, energy consumption is almost zero because we simply use the ambient light of the surroundings." 

What about commercialization? 

"For reflective screens to compete with the energy-intensive digital screens that we use today, images and colors must be reproduced with the same high quality. That will be the real breakthrough. Our research now shows how the technology can be optimized, making it attractive for commercial use," lead author Marika Gugole said.  

Gugole is a doctoral student in the Department of Chemistry and Chemical Engineering at Chalmers.