A new coating made of germanium, which separates the photovoltaic and thermal bands of sunlight, increases the efficiency and service life of photovoltaic cells.
Cleveland (USA). The lifespan of current crystalline solar cells is estimated to be around 30 years. However, the efficiency of photovoltaic systems decreases with increasing age . When it comes to quality cells, manufacturers usually give a performance guarantee of 80 percent after 25 years.
Scientists from Case Western Reserve University (CWRU) and the University of Rochester (UR) have now presented a new coating designed to increase the service life of photovoltaic cells and the efficiency of the cells.
15 nanometers of germanium
According to their publication in the journal Nature Nanotechnology , the coating made of the semimetal germanium is only 15 nanometers thick. Their optical properties make it possible to separate the photovoltaic and thermal bands of sunlight. The coating can therefore simultaneously reflect and transmit colors or wavelengths of light. Previous coatings could only do one of them.
No overheating of the solar cells
The new coating can therefore transmit the photovoltaically relevant areas of light from which the solar cells generate electricity, while the thermal bands of the light are reflected. “If only the usable area of the solar spectrum is directed at a solar cell, it will prevent it from overheating,” explains Chunlei Guo. Experiments measured a low 30 degrees Celsius. According to Giuseppe Strangi, such a temperature could enable photovoltaic cells to have an “up to six times longer service life”.
According to Guo, the energy of the reflected thermal bands of sunlight can also be used, for example for water treatment or water heating. It is also possible to store the thermal energy to generate electricity at night.
Other possible uses of the optical coating
“These optical coatings can clearly do a lot more that other coatings cannot,” explains Guo. “We have done something that has not yet been done in a century of the development of optical coatings – and even we do not know all the applications that could result from them,” adds Strangi.
According to its developers, further experiments are necessary to find out which uses the new optical coating can still be used. As Guo explains, “it will be a while before we or other laboratories investigate this further and find further applications.”