Researchers have discovered a method to enhance the performance of cuprous oxide semiconductor materials by a twist, potentially replacing silicon in photovoltaics at a lower cost. The findings were published in Nature on April 24.
Cuprous oxide and cupric oxide are inexpensive and abundant semiconductor materials with good electrical and optical properties. They can be used in manufacturing solar cells, optoelectronic devices, sensors, and are considered potential alternatives to mainstream silicon semiconductors.
However, while cuprous oxide and cupric oxide are effective in capturing sunlight and converting it into charge, they tend to lose charge easily, limiting their performance.
The study published in Nature suggests that low-cost materials also hold promise in driving the transition from fossil fuels.
"Like other oxide semiconductors, cupric oxide has its inherent challenges," said Linfeng Pan, co-first author of the paper and a Ph.D. student in the Department of Chemical Engineering and Biotechnology at the University of Cambridge. "One challenge is the contradiction between the depth of light absorption and the distance charge travels within the material, with much of the oxide beneath the material's top layer essentially being a 'dead zone.'"
Professor Sam Stranks, leading the research at the University of Cambridge, noted that for most solar cell materials, surface defects lead to performance degradation; however, the situation is the opposite for oxide materials: while the surface looks good, internal defects cause performance losses.
"This means that the way crystals grow is crucial to their performance," Stranks explained.
To optimize material performance, researchers used thin film deposition techniques to prepare high-quality cupric oxide crystal films at room temperature and pressure. By precisely controlling crystal growth and flow rates, they "twisted" the material, changing the crystal growth direction to diagonal. Subsequently, high-resolution spectroscopy was used to observe how the crystal growth direction affects the effective movement of charge within the material.
"These crystals are essentially cubes, and we found that when electrons traverse the cube along its body diagonal rather than along the surface or edge, their movement distance significantly increases. The farther electrons move, the better the performance," Pan stated.
"The diagonal direction of these materials is remarkable," Stranks remarked. "Further work is needed to fully understand the reasons and optimize it, but so far, it has led to a significant leap in performance."
Testing of cupric oxide optoelectronic cathodes manufactured using this technique showed a performance improvement of over 70% compared to the most advanced electrochemically deposited oxide cathodes. Additionally, stability was greatly enhanced.
Researchers emphasized the need for further research and development, but believe that this material and its related material family could play a crucial role in energy transition.
"There is still a long way to go, but we are on an exciting trajectory," Stranks concluded.
The research involved scientists from the University of Cambridge in the UK, École Polytechnique Fédérale de Lausanne in Switzerland, Nankai University in China, and Uppsala University in Sweden.
For more information, refer to the related paper: https://doi.org/10.1038/s41586-024-07273-8
