In the mid-1880s, Charles Fritts built the first solar cell formed by selenium coated with a thin layer of gold and with an energy efficiency of 1%. However, it was not until 1954 that Bell Labs discovered accidentally that would be the first commercial solar cell, with silicon as the base. Since then, the solar cell technology has evolved significantly and today, the future is based on the cells ‘photosynthetic’, a system that mimics the activity of chlorophyll in the leaves of plants. In this work the group ‘Colloids and nanostructured solar cells’, headed by Juan Antonio Anta, University Pablo de Olavide.
Currently in use in research laboratories differentiated three generations of solar cells, which provide different solutions to same problem: using the sun or solar as a renewable energy source. The most common, those of silicon, were the first to hit the market and are also the most advanced from a technical standpoint, for his long career.
Evidence of this is that despite having served 54 years, still continues to work with them. In this sense, the ultimate is to obtain the so-called ‘black silicon’ by researchers from Harvard University, which will manufacture solar cells with sensitivity to light, estimated between 100 and 500 times higher than silicon normal.
The second step has been taken in this respect are the thin-film cells. Continuing the use of inorganic materials, which again underlines the silicon in several variants, these boards have so far had a significantly lower efficiency than the previous generation, but have a good performance in space.
However, the latest line in this field open commitment to the use of organic materials. And is that the difficulty of obtaining quality inorganic elements necessary to serve as a photovoltaic material makes these devices too expensive. Therefore, from the Pablo de Olavide University is working within the framework of several projects, including the Hope Consolider Ministry of Science and Innovation, in optimizing the call Grätzel cell, which mimics the phenomenon of artificial photosynthesis and has, according to tests performed by different laboratories, an efficiency of 11%.
Broadly, Grätzel cells are photovoltaic panel devices introduced in the early ’90s, taking advantage of the combination of a nanos tructured semiconductor (titanium dioxide, mainly) and an organic dye that serves as a collector of sunlight. This dye, as reported by the research team, Elena Guillen, can be both synthetic and natural, and even allows the use of chlorophyll in these cells.
Opting for Ionic Salts
“In recent months we have worked with dyes such as eosin or Mercurochrome, xanthene derivatives, heterocyclic organic compound, but now we are focusing on a separate line, which is based on ionic liquids, the famous green solvents” notes the researcher.
This change is being investigated because, in addition to finding the most suitable dye, an important aspect addressed in this type of technology is the problem of evaporation of liquid compounds in cells. For this, the group led by Anta teacher is working with different types of ionic salts that have the characteristic of not evaporate at room temperature.
Pros and Cons of the New Generation
Although offered for sale are some third-generation solar cells (eg, to recharge cell phones), its practical use is anecdotal, the researchers said. However, their flexibility and variety of colors and shapes the future of these cells is in new market niches that pass through the decoration or use in colored windows that let in light while, used to generate electricity.
Moreover, the rapid recovery of the energy cost of production, it is estimated that within a year of use-it adds a low cost with respect to the materials. “The organic, usually, often cheaper,” says the researcher, although that is still working to find an alternative to organic dye currently used, derived from ruthenium. “The paradox is that if you use these cells because their point is competitive with silicon that are cheaper and widely available, but use as a color one based on precious material, what is the advantage?” Says Elena Guillen.
