Researchers at the Karlsruhe Institute of Technology (KIT) are studying the use of semi-transparent photovoltaics with precisely adjustable absorption properties, which would increase the overall efficiency of solar panels.

The project establishes that by combining new materials with targeted component design, the absorption of incident light in precisely defined spectral ranges can be achieved with a semi-transparent solar cell.

Organic solar cells use carbon-based semiconductors, typically characterized by narrow-band absorption ranges, making them the best suitable option for use on glass windows of buildings and in agriculture.

The new material concepts and innovations in organic semiconductors are paving ways to achieve higher application-specific efficiency.

Organic semiconductors enable controlling the absorption properties of organic solar cells, according to Christian Sprau from KIT’s Light Technology Institute.

For example, Sprau explained, “In agrivoltaics, only the wavelengths required for growth have to reach the plants, whereas they can be protected from other spectral components of the light and thus be prevented from drying out. On the other hand, the window front of a high-rise building only has to let through the light that the human eye perceives as brightness. In both cases, high energy harvests can be achieved simultaneously with the unused portions of the sunlight.”

With the development of novel acceptors — the electron-accepting molecules in the light-absorbing layer of solar cells — scientists have achieved up to 20% efficiencies in laboratory settings.

The KIT researchers further claimed that double use of space by photovoltaics would play an important role in enabling Germany and Europe to achieve climate neutrality in good time.

In a similar study aimed at improving organic solar cells’ efficiency to maintain long-term stability, scientists at the University of California found that addressing the issue of electron donor polymer chain twisting can enable these cells to produce affordable and efficient energy over the long term.

Earlier, a team of material scientists at the UCLA Samueli School of Engineering in California designed a solar roof with semi-transparent solar cells for a miniature greenhouse prototype, producing sufficient energy from sunlight to grow plants or crops.