Thin-film solar cell technology, based on printable plastic polymers, holds promise of becoming the next wave of cheap, reliable clean energy for the solar sector.

But until efficiency levels can compete with those of conventional silicon modules, the hope of one day covering entire buildings with flexible transparent solar panels remains in the distant future.

This challenge has spurred researchers from the University of Adelaide’s Chemistry Department to study the molecular nature of these conductive plastics to better understand how they absorb and convert light into energy.

They aim to tune the molecules up to a level where they harvest more photons from the sun, making them more energy efficient.

“There is a whole category of new ‘plastic’ materials, called organic semi-conductors and, like normal plastics, they are made from hydrocarbon chains or polymers. But unlike normal plastics, they can conduct electricity,” explains lead researcher Patrick Tapping, PhD candidate in the School of Physical Sciences.

“These materials are flexible and cheap to manufacture – they can be printed out as giant sheets. But at the moment they are not currently very good at turning absorbed light into harvestable electricity. They don’t transport electrons to electrodes as efficiently as they should.”

The team are using ultra-fast laser spectroscopy to shoot rapid pulses of light into polymer solar cells and measuring the reactions on a molecular level with an electronic detector. A sophisticated computer model then allows the researchers to “watch” the results occurring at an atomic level.

“We’re conducting experiments and using computer simulations to look at the arrangements of the polymer chains to see how they affect the electricity-generating properties of the materials,” says Tapping.

“By the speed and intensity of the changes to light-absorption, we can gain insight to where potential sources of energy loss may be occurring. This can then guide changes in order to better harvest the sun for more efficient energy generation.”

Tapping and his supervisors, Dr Tak Kee and Dr David Huang, hope their work will help further the dream of office blocks coated with giant semi-transparent solar films, providing enough energy to power entire buildings.

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