Producing renewable energy from silicon solar cells costs more than twice as much as using other "green" sources, such as wind and natural gas. For example, a typical polycrystalline silicon photovoltaic cell produces electricity at a cost of around 20 cents/kWh (spread over a 20-year lifetime) while electricity derived from wind and natural gas costs roughly 4–10 cents/kWh and 5–7 cents/kWh respectively. So it is important to reduce the cost of solar cells before they can be used around the world as a source of low-carbon energy. Indeed, the price of silicon may need to drop by three orders of magnitude before this can happen, says team member Cyrus Wadia.
To investigate possible alternatives to silicon, the researchers analysed 23 promising semiconducting materials for photovoltaics, looking at their availability and how expensive it is to extract them compared to silicon. They did this by developing a model that evaluates the maximum amount of energy that each different semiconductor can produce in a year. The model calculates power conversion efficiency and minimum material intensity (the absolute minimum mass of semiconducting material needed to absorb 85% of incoming sunlight).
The team found that 12 of the materials studied have the capacity to meet, or even exceed, the annual worldwide electricity consumption of 17,000 TWh. What's more, nine could be significantly cheaper than crystalline silicon. The best materials appear to be iron sulphide and copper sulphide, and copper oxide, says Wadia.
Previous work on these materials for use in photovoltaics found that they suffered from low efficiencies. However, there is a trade-off between efficiency and how the material is used, explains Wadia. "We may still benefit from technologies that have a lower efficiency than those commercially available today if we build them with far less material," he told environmentalresearchweb.
Traditionally, solar-cell scientists have only focused on performance and cost and haven't really considered scale. "It is one thing to make a nice solar cell, but an entirely different thing altogether to develop solar technology that can be dispatched to seven billion people," added Wadia. "We performed this study to find overlooked materials that could be the best choice in all ways. And we found the metal sulphides to be just that."
The team is now working in the chemistry laboratory to try to develop these materials further and to look at their toxicity compared with silicon, which is, of course, non-toxic and highly abundant on Earth.
The work was published in Environmental Science and Technology.
1 comment
Comments on this article are now closed.
Comments on this article are now closed.