Researchers have demonstrated how a non-toxic alternative to lead could form the basis of next-generation solar cells.
The team of researchers, from the University of Cambridge and the United States, have used theoretical and experimental methods to show how bismuth – the so-called “green element” which sits next to lead on the periodic table, could be used in low-cost solar cells. Their results, reported in the journal Advanced Materials, suggest that solar cells incorporating bismuth can replicate the properties that enable the exceptional properties of lead-based solar cells, but without the same toxicity concerns. Later calculations by another research group showed that bismuth-based cells can convert light into energy at efficiencies up to 22%, which is comparable to the most advanced solar cells currently on the market.
Most of the solar cells which we see covering fields and rooftops are made from silicon. Although silicon is highly efficient at converting light into energy, it has a very low “defect tolerance”, meaning that the silicon needs to have very high levels of purity, making it energy-intensive to produce.
Over the past several years, researchers have been looking for materials which can perform at similar or better levels to silicon, but that don’t need such high purity levels, making them cheaper to produce. The most promising group of these new materials are called hybrid lead halide perovskites, which appear to promise a revolution in the field of solar energy.
As well as being cheap and easy to produce, perovskite solar cells have, in the space of a few years, become almost as energy-efficient as silicon. However, despite their enormous potential, perovskite solar cells are also somewhat controversial within the scientific community, since lead is integral to their chemical structure. Whether the lead contained within perovskite solar cells represents a tangible risk to humans, animals and the environment is being debated, however, some scientists are now searching for non-toxic materials which could replace the lead in perovskite solar cells without negatively affecting performance.
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