40-year-old major flaw in solar panel efficiency finally discovered

4 Jun 2019

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A defect that has left solar panel efficiency lower than what we want has been discovered, solving a 40-year-old mystery.

In our efforts to produce greater quantities of renewable energy, solar is just one method that has expanded significantly in use over the past few decades. However, the majority of solar cells only achieve efficiency of approximately 20pc, meaning much of what’s harnessed from the sun goes to waste.

Now, in a paper published to the Journal of Applied Physics, a team of scientists from the University of Manchester has announced the discovery of a solar cell flaw that could dramatically improve efficiency. The inefficiency problem has plagued engineers and researchers for more than 40 years and, despite being known about, more than 270 research papers have been published with no solution to the problem.

Highlighting the scale of the problem, Prof Tony Peaker, who coordinated this research, said: “During the first hours of operation, after installation a solar panel’s efficiency drops from 20pc to about 18pc.

“An absolute drop of 2pc in efficiency may not seem like a big deal, but when you consider that these solar panels are now responsible for delivering a large and exponentially growing fraction of the world’s total energy needs, it’s a significant loss of electricity-generating capacity.”

Time for an engineering fix

This new discovery, however, highlights a previously unknown material defect in silicon solar cells in the mechanism responsible for light-induced degradation. Using a specialised electrical and optical technique known as deep-level transient spectroscopy, the team uncovered the defect that initially lies dormant within the silicon used to manufacture the cells.

The electronic charge within the bulk of the silicon solar cell is transformed under sunlight as part of its energy-generating process. Yet the team found that this transformation involves a highly effective ‘trap’ that prevents the flow of photo-generated electrons.

Researcher Dr Iain Crowe explained: “This flow of electrons is what determines the size of the electrical current that a solar cell can deliver to a circuit.

“Anything that impedes it effectively reduces the solar cell efficiency and amount of electrical power that can be generated for a given level of sunlight. We’ve proved the defect exists; it’s now an engineering fix that is needed.”

Colm Gorey was a senior journalist with Silicon Republic