LCD screen harvests energy from indoor and outdoor light

Researchers have developed an LCD screen that harvests electrical energy from ambient light, sunlight and its own backlight using a built-in photovoltaic polariser.

Liquid crystal displays (LCDs) work by using two polarised sheets that let only a certain amount of a device’s backlight pass through. Tiny liquid crystal molecules are sandwiched between the two polarisers and these crystals can be switched by tiny transistors to act as light valves. Manipulating each light valve, or pixel, lets a certain amount of the backlight escape; millions of pixels are combined to create images on LCDs.

From the perspective of energy use, current LCD polarisers are inefficient. A device’s backlight can consume 80 to 90 per cent of the device’s power. But as much as 75 per cent of the light generated is lost through the polarisers. A polarising organic photovoltaic LCD could recover much of that unused energy.

A team at the University of California Los Angles (UCLA) has created and tested a screen that it claims is the first such device to be able to simultaneously act as a polariser, a photovoltaic device and an ambient light or sunlight photovoltaic panel.

The polarising organic photovoltaic cell demonstrated by the research group can harvest up to 75 per cent of the wasted photons from LCD backlight and turn them back into electricity, the team claims.

‘In addition, these polarisers can also be used as regular solar cells to harvest indoor or outdoor light. So next time you are on the beach, you could charge your iPhone via sunlight,’ said project lead Prof Yang Yang of UCLA.

‘In the near future, we would like to increase the efficiency of the polarising organic photovoltaics and eventually we hope to work with electronic manufacturers to integrate our technology into real products,’ he added.