Rigid Electron Polymer Chains Could Boost Efficiency of Organic Solar Cells

Researchers studied degradation mechanisms of electron donor and acceptor materials


In a new experiment aimed at improving organic solar cells (OSC) efficiency to maintain long-term stability, scientists found that addressing the issue of electron donor polymer chain twisting can enable these cells to produce affordable and efficient energy over the long term.

In the new work published in the journal Joule, research teams from the University of California Cavendish Laboratory and scientists from the United Kingdom, Belgium, and Italy focussed on the degradation mechanisms for two components used in the light-absorbing layer of organic solar cells: the electron donor and electron acceptor materials.

These two components are needed to split the bound electron-hole pair formed after the absorption of a photon into the free electrons and holes that constitute an electrical current.

They observed polymer twisting in three donor polymers to measure the charge generation yield.

The teams subjected the operational solar cells to ultrafast laser spectroscopy with its illumination equalling that of the sun and discovered that the donor polymer chain twists as a reaction to extreme heat.

The twisted polymer absorbed a photon and underwent an extremely rapid deactivation pathway on femtosecond timescales – a millionth billionth of a second.

The researchers concluded that designing new electron donor materials with more rigid polymer backbones could help reduce the propensity of the polymer to twist and improve the stability of the organic solar cell.

According to the lead author of the paper Alex Gillett, “It was interesting to find that something as seemingly minor as the twisting of a polymer chain could have such a large effect on the solar cell efficiency.”

While organic solar cells exhibit potential for clean energy applications, photovoltaic modules made from organic semiconductors do not maintain long-term efficiency under sunlight for real-world applications.

The researchers claimed that their findings pave ways to drive the design of more stable materials for organic semiconductor-based photovoltaics, thus enabling cheap and renewable electricity generation.

Last month, a team of material scientists at the UCLA Samueli School of Engineering in California claimed to have designed a solar roof with semi-transparent solar cells for a miniature greenhouse prototype, producing sufficient energy from sunlight to grow plants or crops.

In another similar experiment, researchers at IIT Kanpur claimed to have developed organic solar cells consisting of a combination of an organic polymer and PCBM — an organic semiconductor — on steel substrates that can possibly convert a steel roof into an energy-producing device.


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