For the past five years, a team of scientists Iowa State, headed by Malika Jeffries-El, has been researching polymers to be used as semi-conductors.

Polymers are created by linking small organic molecules together in a string to create a larger molecule, which is the polymer itself.

“One of the easiest analogies I use to describe polymers is a pearl necklace,” said Jeffries-El, assistant professor of chemistry at Iowa State. “It’s a long strand of material — a molecule. A big molecule that’s made up of a bunch of small molecules linked together. So the pearl would be the critical building block to make the polymer and the pearl necklace itself would be the actual polymer.”

To give the polymers different properties, various organic molecules are bonded together using chemical reactions.

These semi-conducting polymers are being developed to make new materials for light-emitting diodes, also known as LEDs, and for solar energy conversion in photovoltaic cells.

There are currently many products that act as semi-conductors made out of inorganic materials. The advantage of using polymers is that the organic molecules they are made out of occur in higher natural abundance, and that properties can be modified by literally editing the components.

The specific type of polymers Jeffries-El’s team works with are commonly known as heterocyclic compounds. These compounds are easy to create, which makes this particular kind of polymer fairly cheap to produce.

Out of the two dozen new polymers they’ve created, Jeffries-El’s team has discovered one that may be useful in LEDs.

“Based on our initial results, we’re going back to lab, making some modifications to the structure [and] making the second version that should be better,” Jeffries-El said. “But we see some promise in this one for making materials for light-emitting diodes.”

If an LED is used for household lighting, the polymer needs to produce white light.

This, according to Jeffries-El, is difficult. The color that the polymer Jeffries-El’s team has created, however, is blue. This blue polymer can eventually be used to create the LEDs that go into displays like those on TVs.

To create the correct color of the blue, the polymer’s color needs to be within a certain range of color coordinates on the CIE Coordinate Chart, an international map of color coordinates. The blue trying to be obtained, called deep blue, is defined by a certain range of coordinates that the polymer needs to match to be of good enough quality for use in displays. Luckily, for the Jeffries-El team, deep blue is just a few coordinates away.

“Of the three primary colors, blue, it turns out, is one of the ones that is most problematic. There are very few materials that truly emit blue light and the ones that do tend to have what we call a shorter lifetime than the others,” Jeffries-El said.

Currently, the blue light-emitting polymers being created for use in TV displays have lifetimes that are much too short for average consumer needs. Fortunately for the team, there is evidence that this particular polymer — while not quite the right shade and brightness yet — is much more stable than other organic compounds that are being studied for use in LEDs, and will therefore emit light for a longer period of time.

With all the effort that has gone into developing these polymers, the team is excited to have perhaps found a stable blue polymer for use in displays.

“It is really awesome to take what amount to white powders and clear liquids bought from a chemical vendor and through organic synthesis transform them into functional materials,” said Jared Mike, a former graduate student who worked for Jeffries-El. “To see those materials actually function in a device, and add to the understanding of the operation of those devices is very rewarding.”