Advancing Solar Technology: Michigan Tech’s Breakthrough in Quantum Dot Solar Cells

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Professor Yoke Khin Yap and his research group are advancing the efficiency of solar cells, one quantum dot at a time. As the world strives to power its digital future sustainably, the demand for more efficient renewable energy sources is crucial. Researchers at Michigan Technological University are leading a significant breakthrough with their development of highly efficient quantum dot solar cells.

The increasing global electricity demand, driven by our expanding digital infrastructure and the energy-intensive data centers that support it, has made efficient renewable energy production more important than ever. In response to this challenge, Michigan Tech researchers have charted a new course toward scalable and efficient solar energy solutions. Their recent research, published in *ACS Applied Energy Materials*, focuses on fundamental solar cell design principles, prioritizing material quality over structural complexity.

Led by Professor Yoke Khin Yap, experts in physics and materials science and engineering at Michigan Tech conducted this pivotal study. Traditional commercial solar cells primarily use expensive single-crystal silicon, which poses significant scalability issues for large-area devices. Over the past two decades, much of the research has concentrated on enhancing electron transport layers (ETLs) through nanostructuring to increase surface area and electron flow. However, this innovative approach has inadvertently resulted in more interface defects, ultimately hindering solar cell performance.

Quantum dot (QD) solar cells offer a promising alternative, thanks to their cost-effectiveness and scalability in manufacturing. Nevertheless, these emerging technologies have encountered challenges with efficiency losses at the material level and defects in transport layers. By returning to basics and focusing on thin-film quality, Yap’s research group successfully enhanced the electrical transport efficiency in QD solar cells. They achieved an impressive efficiency of 11% by employing a ultraviolet (UV) laser technique to create higher-quality thin films, with the potential to double the performance by integrating additional types of QDs.

Yap’s team utilized UV pulsed-laser deposition (PLD) to enhance the quality of both the electron transport layers (ETL) and the hole transport layers (HTL), which are vital for energy flow in a solar cell. They employed cadmium selenide quantum dots to capture sunlight, with zinc oxide serving as the ETL and molybdenum trioxide functioning as the HTL. These materials were chosen for their stability against humidity, making them suitable for practical applications. The UV laser technique results in higher-quality ETL and HTL thin films with fewer defects, reducing charge trapping and improving electron flow. This method achieved an 11% conversion efficiency using only one type of QD, marking a significant improvement over previous cadmium QD solar cell designs.

“ETL nanotechnology is interesting, but there is significant potential to improve thin films for both the ETL and HTL,” Yap noted. “We achieve 11% conversion efficiency using only one type of QD. Theoretically, we could enhance, if not double, the efficiency by adding another type of QD, surpassing the efficiency of commercial solar panels.”

Using the UV PLD method, Yap’s laboratory previously demonstrated the formation of various nanostructures and quantum materials at room temperature, facilitated by the fine and energetic vapors produced by the UV pulsed laser. Future research will focus on integrating different types of QDs while maintaining the same electrical transport efficiency achieved with the single-dot system.

This research is supported by the MTU Elizabeth and Richard Henes Center for Quantum Phenomena and the University’s Jim ’66 and Shelley Williams Applied Physics Annual Fund. The published article was also selected as a supplementary cover graphic for *ACS Applied Energy Materials*.

Michigan Technological University, founded in 1885 and located in Houghton, is an R1 public research university with nearly 7,500 students from over 60 countries. Consistently ranked among the top universities in the U.S. for return on investment, Michigan Tech offers more than 185 undergraduate and graduate programs across various fields, including science, technology, engineering, and the arts.
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