Lead-free perovskite and ferroelectric, the new solar promise?
(Sustanabilityenvironment.com) – Could ferroelectric photovoltaics be the next generation of solar devices? There are those who are convinced of this despite this technology having more failures than successes. A group of scientists in the United States is advancing research in this direction thanks to the study of a new crystalline material belonging to the halide perovskite class.
Synthetic perovskites are enthusiastically researching optoelectronics to compete with “classic” semiconductors. In a few years, in fact, perovskite solar cells have reached efficiencies that required, instead, several decades of crystalline silicon. Scientists at the Lawrence Berkeley National Laboratory (Berkeley Lab) of the Department of Energy, in collaboration with the University of Berkeley, have now identified a perovskite with ferroelectric properties. Why is this important progress? Because ferroelectric materials are characterized by a switchable spontaneous polarization. To understand what it means, you have to take a few steps back.
The advantages of ferroelectric photovoltaics
To generate electricity, solar cells need an electric field that separates positive from negative charges. The fv industry achieves this by doping semiconductors with chemicals so that one layer of the device carries a positive charge and another layer a negative charge. This design ensures that electrons flow from the negative to the positive side, a key factor for the stability and performance of the device. But chemical doping and layered synthesis also add extra and expensive steps in production.
In ferroelectric photovoltaics, the semiconductor is already equipped with a built-in electric field, without the need for doping. The new material cultivated in the laboratories of Berkeley is a compound of cesium and germanium – CsGeBr3 or CGB – and is also a lead-free halide perovskite. “If you can imagine a lead-free solar material that not only collects energy from the sun but also has the added benefit of having a naturally and spontaneously formed electric field, The possibilities in the photovoltaic and electronics industry are quite exciting,” said Peidong Yang, co-author of the research published in the journal Science Advances.
Among the various tests carried out on the CGB, the one on photoconductivity measurements produced a surprising result. The researchers found that the absorption of light in the material is tunable, ranging from the visible spectrum to the ultraviolet, an ideal range for the efficiency of solar cells. An aspect, explain the researchers, that is rarely found in ferroelectric photovoltaics.