Improved semiconductors convert sunlight into hydrogen

These semiconducting materials, known as copper oxide (Cu2O), are inexpensive and non-toxic and have long been of interest as a material for directly converting sunlight into hydrogen from water. However, their performance has not been on a par with conventional technology using silicon solar cells linked to an electrolyser that generates the hydrogen.

“Now we have considerably improved performance by developing a new method of producing the copper oxide material,” says Anders Hagfeldt.

Best possible quality

Using a solution-based process, the researchers were able to produce single-crystalline films of copper oxide, which optimises the quality of the semiconductor material. They also provide unique opportunities to study the fundamental processes of light capture, conversion and transport of electric charges in the copper oxide, as well as the process of generating hydrogen from an aqueous solution.

“We have been able to show that the charges move more rapidly and more efficiently in certain directions in the copper oxide crystal and that a certain specific surface yields the best efficiency for conversion into hydrogen,” Hagfeldt continues. “Our tests showed a 70 per cent improvement over the best published results to date for copper oxide. Stability also improved significantly.”

According to the researchers, the results show how low-cost materials can be produced with high-quality properties to drive the transition from fossil fuels to clean and sustainable fuels that can also be stored. They argue that these types of materials can play a crucial role in the energy transition, though much research still remains to be done.

Märta Gross Hulth