Three organic light-emitting transistors displaying different patterns of green light

Devices that include light-emitting semiconductors display a variety of patterns when illuminated by a laser. Credit: L. Hou et al./Nature Nanotechnol.

Materials science

Lasers control a mini-light show

Device achieves resolution thousands of times higher than current display screens.

Researchers have devised a method for creating low-cost, ultra-high-resolution ‘smart’ displays that can be remote-controlled by a laser.

Paolo Samorì at the University of Strasbourg, France, and his colleagues designed light-reactive molecules that, under either ultraviolet or visible light, change to an alternate structure. This reversible switch also changes the molecules’ electronic properties. The team blended the molecules with semiconducting, carbon-based polymers that produce red, green or blue light when a current runs through them.

The team deposited the mixture around interlocking electrodes, and then applied voltage and a green laser to the resulting device. The laser triggered a change in the light-reactive molecules’ structure, which allowed current to flow within the device. That prompted the semiconductor to emit light; training an ultraviolet laser on the device turned the light off.

Using this technique, the team was able to write and erase light emissions with a resolution that, in a display, would be more than 3,000 times better than that of the sharpest displays on the market. The researchers could also control the emission’s brightness and colour.

Because the laser also manipulates the device’s current output, the technique could provide a new way of using light to control other devices, such as digital memory technologies, say the authors.