Hybrid solar cell also supplies electricity at night

A team led by Kasper Moth-Poulsen from the Barcelona School of Engineering has developed a hybrid cell that stores part of the sun’s rays in the form of chemical energy. This can then be used as electrical current after sunset using a thermocouple.

Loss radiation used

The hybrid cell consists of two levels. At the top there is a system called “MOST”, below which is a conventional silicon solar cell, which, as usual, converts part of the sunlight spectrum directly into electricity. MOST uses photons that cannot be used by the solar cell and are normally lost. And MOST captures this radiation and only allows the part of the sunlight that can be used for photovoltaics to pass through.

MOST consists of organic molecules made up of common elements such as carbon, hydrogen, oxygen and nitrogen, and is therefore very inexpensive. They change their structure under the influence of the high-energy photons and at the same time prevent the solar cell underneath from heating up. The temperature reduction is eight degrees Celsius. This means that the solar cell maintains a high level of efficiency – this decreases the more it gets warmer.

Development continues

There is still room for improvement in terms of efficiency. MOST comes in at 2.3 percent, the solar cell at 12.6 percent. This means that just 14.9 percent of the sunlight is converted into electricity. But this is the world’s first hybrid cell of its kind, so significant improvements in efficiency are to be expected. For example, MOST could be made more transparent so that more usable sunlight falls on the silicon cell. Or the composition of the organic storage material could be changed to capture more high-energy photons.

If the scientists succeed in increasing the efficiency of the MOST system in particular, the hybrid cell would become serious competition to batteries that are used to bridge weather-related power gaps. These are expensive and contain problematic materials such as lead or cobalt.