Solar power has been for many years one of the fastest growing energy sources coming to represent 2% of the world’s generated electricity in 2018. By the end of that year there was enough installed capacity worldwide to generate 640 terawatts-hour of electricity per year. A larger deployment of solar projects and technology advances has allowed for cost reductions in solar and other renewables to the point where these technologies represent the cheaper option for new power generation capacity in some markets.
The sun provides us with virtually endless energy; but we only harness a minuscule fraction of that. A breakthrough in a new material for solar panels could help us harness more energy thanks to advances in perovskite cells.
Perovskite is a type of crystal which characteristics like high superconductivity, magnetoresistance and ferroelectricity make it attractive to be used in solar cells. Perovskite cells have excellent absorption of incident light even with a very thin perovskite layer and a sharp optical absorption edge which reduces energetic losses. They can also operate with single-junction or multi-junction technologies and are suitable for different applications (small and utility scale solar).
The main advantage for the development of perovskite solar cells is the potential efficiency achieved with this material, plus the components are cheap compared to crystalline silicon which remain the most commercial type of cells. Perovskite cells have reached a 23% power conversion efficiency on a laboratory-scale; in comparison, silicon solar cells that are currently on the market range from 17 to 26% efficiency rating for the most expensive ones. The National Renewable Energy Laboratory NREL along with scientists from the University of Toledo and University of Colorado has achieved the 23% efficiency mark but the laboratory is working on a composite silicon-perovskite cell to create a multi-junction solar cell that could reach 27% efficiency. The most efficient perovskite cells use an absorber layer, 300 to 600 nanometers, which is almost three times thinner than silicon solar cells.
Although perovskite solar cells are promising, the technology still requires further improvements. Some of the main issues that hinder commercialization include thermal stability, ambient degradation (particularly moisture), cell size and toxicity of the components. The most efficient cells use lead-based halide perovskite. The presence of lead is a source of concern because of its toxicity which can become apparent during operation as it could affect stability and also at end of life.
To date, there are only a few pilot lines producing perovskite solar cells; but numerous manufacturers and research institutes are heavily investing to advance the technology and increase power conversion efficiencies as well as pursuing lead-free alternatives or improving recycling methods for lead-based perovskite cells. According to an IHS Markit forecast, perovskite cells will be ready for commercialization in the next 3 to 5 years.
IHS Markit, P.Boix et al. Working principles of Perovskite Solar Cells (2019), W.Ke & M.Kanatzidis. Prospects for low-toxicity lead-free perovskite solar cells (2019), OilPrice.com
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