A key solar panel defect has been resolved, which can lead to a significant drop in prices

MIn addition, silicon: an alternative material for solar panels is gaining efficiency, which could result in designs and lower prices so low that they beat fossil fuels.

A researcher from the University of Loughborough has discovered something powerful by exploring cadmium telluride-based panels (a crystalline compound made of cadmium and tellurium): the addition of a new element, Selenium to the mix could help CdTe-based panels produce even more power.

The paper, "Understanding the role of selenium in defect passivation for highly efficient selenium-rich cadmium telluride solar cells," was published in the journal on Monday. Nature Energy.

Cadmium telluride is the second most widely used solar technology in the world; approximately 5% of the market could offer a price advantage over top-ranked silicon due to its manufacturing process. EnergySage notes that cadmium is a byproduct in processes such as the manufacture of zinc, which means that it is relatively abundant, although relatively toxic as well.

These advantages are apparent on the market. Solar panel manufacturer First Solar, based in Tempe, Arizona, claims to have achieved a manufacturing cost per watt of less than 29 cents for its "Series 4" cadmium telluride modules. A standard solar panel, meanwhile, cost about 37 cents per watt at the end of the fourth quarter of 2017.

Silicon currently enjoys an advantage of economies of scale by providing about 95% of global panel production.

Solar panel defects: how a team broke the case

Manufacturers added selenium to cadmium telluride to improve efficiency, from about 19.5% to a new record of 22.1%. But until now, it was not clear Why the addition of this element to the combination has helped increase the efficiency of the panels.

Thomas Fiducia, lead author of the journal and a student PhD student at Loughborough University's Renewable Energy Systems Technology Center, said in a statement, "Although counterintuitive, it's a good, flawless solar cell material. is very effective at emitting light and therefore strongly luminescent ". could use this quirk to show the effect of selenium on energy recovery.

The results were surprising: the team found that selenium overcame a large defect in standard cadmium telluride panels, explaining why selenium was achieving higher yields. Here is the selenium distribution on the left, compared to the luminescence values ​​on the right:

Fiducia tells reverse that the results could benefit other forms of solar panels, or even other technologies dependent on similar processes.

"The lessons learned from this work could potentially be transferable to other solar cell materials, and even to other optoelectronic devices such as LEDs and infrared detectors," explains Fiducia.

This breakthrough could also allow teams to use more selenium to strengthen cadmium telluride panels, perhaps by changing the way they are distributed.

"If efficiency can be improved, it will further reduce electricity prices and have a direct positive impact on regions that adopt the technology," Fiducia said in a statement.

Abstract:

The electricity produced by cadmium telluride (CdTe) photovoltaic modules is the cheapest electricity in the solar industry and is now lower than fossil fuel based sources in many parts of the world. This is due to the recent efficiencies gained from the selenium alloy in the CdTe absorber, which brought the cell efficiency of 19.5% to its current record of 22.1%. Although it is known that the addition of selenium reduces the bandgap of the absorbing material and, therefore, increases the short-circuit current of the cell, this effect alone does not explain improved performance. Here, by means of cathodoluminescence and secondary ion mass spectrometry, we show that selenium allows for higher luminescence efficiency and longer diffusion lengths in the alloy material, indicating that selenium passes through defects. critical in the mass of the absorbent layer. This passivation effect explains the record performance of CdTe devices combined with selenium and is a way to further improve efficiency, which can further reduce the costs of electricity generated by solar energy. .