Researchers develop new material for efficient and sustainable organic solar cells

July 12th, 2016, Published in Articles: EE Publishers, Articles: Energize

 

A team of researchers from Friedrich Alexander University (FAU), Nuremberg, led by photovoltaics researcher and materials scientist Prof. Dr. Christoph Brabec have achieved an important milestone in the quest to develop efficient solar technology as an alternative to fossil fuels.

Fig. 1: Rooftop photovoltaic panels.

Together with colleagues from Imperial College London and the King Abdullah University of Science and Technology (KAUST), they have investigated a new molecule which could be used to increase the lifetime of organic solar cells considerably, while also making them more efficient. In their new technology the researchers succeeded in combining the factors that the energy market considers the most important for producing sustainable energy: module efficiency, lifetime and cost per watt.

Organic solar cells

Organic solar cells are considered a competitive alternative to the standard silicon cells that are currently being used in photovoltaics. They are incredibly thin, flexible and translucent, and can be integrated into window-glass or used by architects as design elements in large lighting installations.

solar-energy-thin-film-solar-cell

Fig. 2: Film film solar cell.

In contrast to the silicon cells that are often installed in photovoltaic systems on the roofs of buildings, organic solar cells are made of special semiconductor-based polymers called fullerenes – minute carbon molecules that look like footballs. Using fullerenes makes the cells highly efficient but also less durable, meaning that they are unable to match the standard technology over periods longer than 30 years, for example. Prof. Dr. Christoph Brabec, Chair of Materials for Electronics and Energy Technology, says the environmental stability of these kinds of solar cells is currently insufficient. However, that is about to change. FAU researchers led by Prof. Brabec and materials scientist Nicola Gasparini, a doctoral candidate at FAU, have now managed to find an alternative to fullerenes.

An alternative to fullerenes

Brabec says the researchers have identified a new organic molecule which is not based on fullerenes. Compared with other acceptors – which are an essential element in photovoltaics – it is in a class of its own in terms of functionality, he says. While fullerenes only absorb a very small amount of light, the new molecule the group have discovered is able to convert a very large amount. The more sunlight absorbed, the higher the efficiency of the cell. Brabec says this is a major breakthrough for the international research community which has been looking for new cell technologies that can replace fullerene, and could reduce the cost of producing solar energy.

According to Brabec, this is what will make producing energy using photovoltaics a competitive alternative to fossil fuels. When determining the cost of producing energy, all of the costs that are required to convert the energy from the source (in this case the sun) into electricity are taken into account.

In their study the researchers demonstrated the record stability and efficiency of their newly developed polymer. Brabec says the group measured a significantly higher air-stability, even at temperatures of up to 140°C, and expects to be able to produce stable solar cells with an efficiency of over 10% using these materials.

Another significant benefit is that the process used to print the new organic materials is less expensive. Instead of using costly semiconductor technologies, the photovoltaic elements, which consist of thin polymer substrates, are produced on a production line where they are printed and coated. In addition, the solar films can be made in different colours. This will give architects greater freedom when choosing colour combinations for their design and enable car manufacturers to install the special organic solar cells in glass roofs in vehicles, for example.

The new technology also opens up a whole new range of possibilities for the chemical industry to improve existing applications and develop new ones. In light of all this, it is clear that the FAU researchers have succeeded in taking a major step forward in solar energy research. These new findings highlight the excellent work and high standards of FAU researchers who work together in interdisciplinary teams, Brabec says. This is considered to be an important milestone in the development of next-generation photovoltaic technologies and is a testament to the group’s superb research skills.

The new solar modules were developed in close collaboration with Dr. Derya Baran from Imperial College London, who spent time researching at FAU after she completed her doctoral degree. The researchers also collaborated with King Abdullah University of Science and Technology (KAUST), Saudi Arabia, and Stanford University, USA.

Contact Prof. Brabec, Friedrich Alexander University, christoph.brabec@fau.de

 

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