Making a better semiconductor

Making a better semiconductor

Everyday items such as solar cells and LEDs could be improved through a new technique developed at The University of Texas at Austin.

Both solar cells and LEDs (light-emitting diodes) are made from plastic semiconductors. UT Austin researchers have developed a new nanoparticle technique that may help plastic semiconductors work better.

As electrical charges travel through plastic semiconductors, they can be trapped the same way a marble rolling on a bumpy surface becomes trapped in a deep hole. These traps of charges are known as “deep traps,” and they are not well understood.

Deep traps can be desired, as in the case of plastic semiconductors used for memory devices, but they can also decrease the material’s ability to conduct electrical charges. In the case of solar cells, deep traps can decrease the efficiency of the conversion of light into electricity.

To further explore the deep trap phenomenon, a group of scientists led by professors of chemistry and biochemistry Paul Barbara and Allen Bard developed a single-particle technique to study small portions of semiconductor material at the nanoscale.

The scientists reported their findings in the advanced online issue of the journal Nature Materials.

“Our results strongly suggest that deep traps are formed in plastic semiconductors by a charge-induced chemical reaction,” says Dr. Rodrigo Palacios, lead author and postdoctoral fellow at the Center for Nano and Molecular Science and Technology. “These traps were not there in the uncharged pristine material.”

Previous techniques used to study deep traps have generally involved completed semiconductor devices, which Palacios says creates complications due to the complexity of a functional device.

Palacios observed deep traps forming as he electrochemically charged and discharged semiconductor nanoparticles with diameters about one-ten-thousandth that of a human hair. The deep traps led to decreases in light emission from the material.