FAU researchers develop new material that can increase the lifetime of organic solar cells considerably

Organic solar cells are expected to replace standard silicon cells used in photovoltaics soon. The organic cells are thin, flexible and translucent and can be used as window glass or a design element by architects.

A team of FAU researchers led by Prof. Dr. Christoph Brabec have achieved an important milestone in the quest to develop efficient solar technology as an alternative to fossil fuels.

Together with colleagues from Imperial College London and the King Abdullah University of Science and Technology (KAUST), they have investigated a new molecule that can be used to increase the lifetime of organic solar cells considerably – while also making them more efficient.

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 longer periods than 30 years, for example. ‘The environmental stability of these kinds of solar cells is not yet sufficient,’ says Prof. Dr. Christoph Brabec, Chair of Materials for Electronics and Energy Technology.

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. They recently published their findings in the journal Nature Communications.

Christoph Brabec said ‘We have identified a new organic molecule that 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.’

While fullerenes only absorb a very small amount of light, the new molecule is able to convert a very large amount. The more sunlight absorbed, the higher the efficiency. This is a major breakthrough for the international research community which has been looking for new cell technologies that can replace fullerene, reducing the cost of producing solar energy said the researchers in a statement.

According to Professor Brabec, this will make producing energy using photovoltaics a competitive alternative to fossil fuels.

Researchers demonstrated the record stability and efficiency of their newly developed polymer. ‘We measured a significantly higher air-stability, even at temperatures of up to 140 degrees,’ Professor Brabec explains. ‘And we expect to be able to produce stable solar cells with an efficiency of over ten percent using these materials.’

Instead of using expensive semiconductor technologies, the photovoltaic elements consisting 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 allow 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 their vehicles.