Solar cell produces hydrogen directly

09.10.2023
Source: Energy & Management Powernews

A research team at the University of Tübingen has developed a novel solar cell that can split water into hydrogen and oxygen with a high efficiency of 18 percent.

The novel solar cell from the University of Tübingen enables decentralized production of green hydrogen and has the potential for industrial-scale applications. So announced the research team led by Matthias May from the Institute of Physical and Theoretical Chemistry at the University of Tübingen. The solar cell is an integral part of the photoelectrochemical apparatus and works directly with the catalysts for water splitting, they said.

In solar water splitting, often referred to as artificial photosynthesis, hydrogen is produced using energy from the sun. With this setup, the demands on the solar cell also become greater. According to the researchers, small crystal defects, such as those that occur when the solar cell layers grow, are particularly difficult. These also change the electronic structure and can thus lower the efficiency on the one hand and the stability of the system on the other.

Overall, corrosion and thus the long-term stability of the solar cell, which is in water, remains the greatest challenge, he said. "Here we have now made great progress compared to our earlier work," May said. What is special about the solar cell's structure is the high degree of control of the interfaces between the different materials. The surface structures here are fabricated and inspected on a scale of a few nanometers.

Solar cell achieves 18 percent efficiency

The efficiency of solar water splitting is measured in terms of efficiency. Here, efficiency indicates the percentage of energy from sunlight that can be converted into usable energy from hydrogen in the form of the fuel's calorific value. With an efficiency of 18 percent, the Tübingen research team presented the second-highest value ever measured for direct solar water splitting with a solar cell, and even a world record if the area of the solar cell is taken into account.

According to the researchers, several spin-offs at other universities with significantly lower efficiencies have since shown that the technology can be commercialized. Erica Schmitt, first author of the study, said, "What we've developed here is a technology of solar hydrogen production that doesn't require a high-power connection to the electricity grid." As a result, he says, permanent, small-scale stand-alone energy supply solutions are also conceivable.

The Tübingen work is embedded in the collaborative H2Demo project, in which the Fraunhofer Institute for Solar Energy Systems (ISE) is involved, among others. The next steps include improving long-term stability, transferring to a lower-cost silicon-based material system and scaling up to larger areas.

Author: Susanne Harmsen