Lower-cost solar cells may spring from WashU model

Inspired by four-decades-old research by a colleague, Cynthia Lo, assistant professor in the School of Engineering & Applied Science at Washington University in St. Louis, has developed a new model to evaluate the performance of a solar panel.

Cynthia Lo, PhD
Cynthia Lo

The aMoBT model, made publicly available through the National Science Foundation's nanoHUB, provides researchers with materials design guidelines that could speed development of lower-cost solar cells. The results of the work were recently published in Physical Review B.

Through one of her co-authors, Joel W. Ager III, staff scientist in the Materials Sciences Division of Lawrence Berkeley National Laboratory, Lo learned that another faculty member at WashU, Daniel L. Rode, senior professor in the Department of Electrical & Systems Engineering, had created a model for evaluating semiconductors in the 1970s.

Lo's research focuses on designing low-cost, transparent semiconducting materials for photovoltaics, which convert solar energy into electricity. Finding the ideal semiconducting material that is both conductive and transparent, yet is abundant in nature, is one of the Grand Challenges recently identified by the U.S. Department of Energy, she says.

"You want your material to act as a window that is transparent enough for light to pass through to the 'more important' layers beneath, but also conductive enough to transport current from the devices to the outside world and produce electricity," Lo says.

Finding these materials would require screening thousands of possible elements and compositions for stability and performance, which would be difficult to conduct experimentally, but could be feasible using theory and computer modeling. That's where the aMoBT computer model comes in.

With Alireza Faghaninia, an Engineering graduate student who works in Lo's laboratory and the first author on the paper, Lo and Ager developed a new computer model that first computes the electronic band structures and density of states for any semiconductor using quantum mechanics, then reformulates equations based on Rode's approach to use these computed values instead of experimental approximations.

"Rode's approach is elegant and based on atomic physics, so it was truly pioneering in the 1970s and is still valuable today," Lo says. "We now have essentially updated the model and made it comparable in effort to the other models that researchers use today. We hope that researchers will realize that our new approach is superior, because it minimizes reliance on experimental data, yet gives results that are quantitatively accurate."



The School of Engineering & Applied Science at Washington University in St. Louis focuses intellectual efforts through a new convergence paradigm and builds on strengths, particularly as applied to medicine and health, energy and environment, entrepreneurship and security. With 88 tenured/tenure-track and 40 additional full-time faculty, 1,300 undergraduate students, more than 900 graduate students and more than 23,000 alumni, we are working to leverage our partnerships with academic and industry partners — across disciplines and across the world — to contribute to solving the greatest global challenges of the 21st century.

Faghaninia, A, Ager JW, Lo CS. Ab initio electronic transport model with explicit solution to the linearized Boltzmann transport equation. Physical Review B, 91, 235123 (2015). http://dx.doi.org/10.1103/PhysRevB.91.235123

Funding for this research was provided by the Solar Energy Research Institute for India and the U.S. (SERIIUS).

Meeting a U.S. Department of Energy Grand Challenge

This research focuses on designing low-cost, transparent semiconducting materials for photovoltaics, which convert solar energy into electricity. Read more.