New quantum theory promises higher efficiency solar cells

30 Jan 2014

Canadian-US partnership driving organic solar cell performance beyond 10%.

A new theoretical model developed by professors at the University of Houston, TX, US, and Canada’s Université de Montréal may hold the key to methods for developing better materials for organic solar cells.

Professors Eric Bittner, of UH's College of Natural Sciences and Mathematics, and Carlos Silva, at the Université de Montréal, say the model could lead to new solar cell materials made from improved blends of semiconducting polymers and fullerenes.

The researchers describe their findings in a paper titled “Noise-Induced Quantum Coherence Drives Photo-Carrier Generation Dynamics at Polymeric Semiconductor Heterojunctions,” published this week in Nature Communications.

Bittner said, “Scientists don't fully understand what is going on inside the materials that make up solar cells. We are trying to get at the fundamental photochemistry or photophysics that describes how these cells work.”

Typically, organic solar cells made from blends of materials reach only about 3% efficiency. Newer materials based on fullerene-polymer blends can raise this figure to about 10%.

He added, “There is a theoretical limit for the efficiency of the ideal solar cell known as the Shockley-Queisser limit. The theory we published describes how we could exceed this theoretical limit by taking advantage of quantum mechanical effects.”

Silva added, “In polymeric semiconductors, where plastics form the active layer of solar cells, the electronic structure of the material corresponds to the vibrational motion within the polymer chain. Quantum-mechanical effects due to such vibrational-electron coupling give rise to many interesting physical processes that can be controlled to optimize solar cell efficiencies.”

The idea for the model was developed while Bittner was a Fulbright Canada Scholar and visiting professor at the Université de Montréal collaborating with Silva, an expert in the field of ultrafast laser spectroscopy and organic semiconductors. Bittner says the benefit of their model is that it provides insight into what is happening in solar cell systems.

The work at UH was funded by the Robert Welch Foundation and the National Science Foundation. The work in Canada was supported by the National Sciences and Engineering Research Council of Canada.

About the Author

Matthew Peach is a contributing editor to optics.org.