To sustainably power our digital future, the world needs more — and more efficient — sources of renewable energy. Michigan Tech researchers are pioneering one such breakthrough in solar energy: highly efficient quantum dot solar cells.
Society’s growing digital infrastructure and the power-hungry data centers required to support it all have dramatically increased global electricity demand, making efficient renewable energy production more critical than ever. At a time when tech companies and governments are seeking sustainable energy solutions, researchers at Michigan Technological University have paved a new path toward efficient, scalable solar energy.
The research, published recently in ACS Applied Energy Materials, represents a return to fundamentals in solar cell design focusing on material quality rather than structural complexity. Michigan Tech experts in physics and materials science and engineering conducted the study, which was led by Yoke Khin Yap, professor of physics.
Commercial solar cells rely on expensive single-crystal silicon, which is difficult to scale for large-area devices. For the past two decades, researchers have primarily concentrated on developing nanostructured electron transport layers (ETLs) to increase contact surface area and enhance electron flow. This approach, while innovative, has unintentionally resulted in more interface defects, ultimately diminishing rather than improving solar cell performance. Quantum dot (QD) based solar cells present a promising alternative due to their cost-effectiveness and manufacturing scalability. However, these emerging technologies have faced challenges with efficiency losses at the material level and defects within transport layers.
By returning to the basics and focusing on thin film quality rather than complex nanostructures, Yap’s research group was able to enhance the electrical transport efficiency in QD solar cells. They developed solar cells that achieved an efficiency of 11% by employing a ultraviolet (UV) laser technique to create higher-quality thin films, and could potentially double the cells’ performance by incorporating additional QD types.
Yap's team’s novel approach uses UV pulsed-laser deposition (PLD) to improve the quality of both the electron transport layers (ETL) and the hole transport layers (HTL), which are essential for the flow of captured energy in a solar cell. Their system utilizes cadmium selenide quantum dots to capture sunlight, with zinc oxide serving as the ETL and molybdenum trioxide functioning as the HTL. These materials were selected for their stability against humidity, making them suitable for real-world applications.
The UV laser technique produces higher-quality ETL and HTL thin films with fewer defects, thereby minimizing charge trapping and enhancing electron flow. This method achieved 11% conversion efficiency using only one type of QD — 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,” said Yap. “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, thanks to the fine and energetic vapors generated by the UV pulsed laser. Future research will focus on integrating different types of QDs while maintaining the same electrical transport efficiency that made the single-dot system successful.
The research is supported by Michigan Tech’s 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 selected as a supplementary cover graphic of ACS Applied Energy Materials.
Michigan Technological University is an R1 public research university founded in 1885 in Houghton, and is home to nearly 7,500 students from more than 60 countries around the world. Consistently ranked among the best universities in the country for return on investment, Michigan's flagship technological university offers more than 185 undergraduate and graduate degree programs in science and technology, engineering, computing, forestry, business, health professions, humanities, mathematics, social sciences, and the arts. The rural campus is situated just miles from Lake Superior in Michigan's Upper Peninsula, offering year-round opportunities for outdoor adventure.
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