The use of solar energy is rapidly increasing as more people look for alternative and renewable sources of energy. One of the main components of solar panels is the contacts that collect and transport the energy generated by the photovoltaic cells. For years, silver has been the primary material for the contacts due to its high conductivity and adhesion properties. However, recent developments have shown that copper may be a better option. This article explores the potential of copper solar panels and the challenges associated with their adoption.
Buried contact solar cells were first introduced in the late 1980s by Australian researchers Stuart Wenham and Martin Green. The contacts used copper instead of silver, and they achieved a record 24.7% efficiency for experimental cells and 20% efficiency for commercial cells. In 1990, a car powered by these solar panels won the World Solar Challenge, which is an annual solar-powered vehicle race through the Australian Outback. The design was revolutionary, and it promised to reduce the cost of solar panels significantly.
Copper has some distinct advantages over silver as a material for solar contacts. Copper is significantly cheaper than silver, which is an important consideration as the demand for solar panels grows. It also has a higher electrical conductivity, which means it can transport energy more efficiently. Copper contacts also have narrower fingers, which means less shading and higher efficiency. With these benefits, copper has the potential to revolutionize the solar panel industry.
Despite the potential of copper solar panels, there are several challenges to their adoption. One of the main issues is that copper is difficult to get to stick to solar panels. Poor contact adhesion has stumped scientists and scared industrialists. Solar panels need to last 25 years and beyond in a variety of climates and in all sorts of weather. Copper’s tendency to peel may reduce the reliability of cells plated with it, so it’s not hard to imagine why manufacturers would be nervous about making the switch.
Another serious concern is performance. While copper contacts may result in higher efficiency, if copper diffuses into the silicon below, the solar panel will experience performance losses. Copper diffusion turns parts of the semiconducting silicon into a conductor, shorting out sections of the panel. In general, the potential for copper diffusion introduces additional risk, which isn’t something you want for a product meant to last for decades. Creating barriers against diffusion is tricky and adds an extra layer of expense in production.
Engineering ways around these problems means adding more steps to the manufacturing process and spending more money, which is one of the main reasons copper hasn’t gained traction, and companies like Suntech and BP Solar failed. Arguably, BP Solar did successfully commercialize its Saturns. In fact, a 2014 study revealed that a group of panels was still working 12 years after their initial deployment with no signs of failure. Researchers couldn’t 100% confirm that the panels hadn’t suffered any copper diffusion, but the data indicates that they were just as durable as their silver counterparts. Despite this, BP had stopped production when its buried contact design couldn’t compete with the lower cost of screen printing silver, which had only gotten cheaper as it evolved.
Despite the challenges, several companies are still pursuing copper solar panels. SunDrive, based in Sydney, is one of them. Their CEO and co-founder, Vince Allen, is a former Ph.D. candidate at the University of New South Wales, where he had been researching copper metallization. After hundreds of attempts, he managed to devise a method of adhering copper to solar cells in thin, densely packed fingers. SunDrive's record-breaking efficiency of 25.54% for commercial silicon solar cells in September 2021 has brought hope for the future of copper solar panels. It broke the previous world record of 25.1% set by the Chinese solar company LONGi Solar in 2019. In December of the same year, SunDrive produced its first full-sized panel, and by September 2022, the company's panel efficiency increased by almost a full percentage point to 26.41%.
SunDrive's CEO, Vince Allen, explained in an interview with the Australian Renewable Energy Agency that small efficiency increases can have "a cascading effect in terms of the final cost" of solar panels. The company prioritizes the residential sector, and with the increased efficiency of their copper panels, they aim to make solar energy more accessible and affordable for homeowners.
SunDrive's success has also caught the attention of industry experts, and another familiar figure, Verlinden, is now on SunDrive's advisory board. Verlinden is the founder of 1366 Technologies, a company that has been working on reducing the cost of solar energy by improving the manufacturing process of solar panels.
However, SunDrive isn't the only company pursuing copper solar panels. In Germany, the Fraunhofer Institute for Solar Energy Systems ISE, Europe's largest solar research facility, has developed its own copper electroplating process. The process has spun off into its own company, PV2+, which aims to establish a pilot program in early 2023.
Bert Thin Films, a startup founded by University of Louisville engineering professor Thad Druffel and former postdoctoral research associate Ruvini Dharmadasa, has also been working on developing copper nanoparticle ink called "CuBert." The team has created a recipe for CuBert that can directly substitute for silver paste without any changes to production tools or a negative effect on the panel's warranty. However, CuBert is still in the testing phase, and the jury is still out on whether it can overcome the challenges of copper oxidation and diffusion.
The use of copper in solar panels is not a new concept, and its potential has been known for decades. However, it has faced several challenges that have made it difficult to commercialize. The most significant challenge is the poor contact adhesion of copper to solar panels, which reduces the reliability of cells plated with it. Copper's tendency to peel also limits its ability to last for 25 years or more, which is necessary for solar panels. In addition, copper diffusion into the silicon below can reduce the performance of the panel, shorting out sections of it.
Despite the challenges, the potential benefits of using copper in solar panels cannot be ignored. Copper is a much cheaper raw material compared to silver, which is widely used in the manufacturing of solar panels. The use of copper could significantly reduce the cost of solar energy, making it more accessible and affordable for consumers. With the success of SunDrive and the development of new technologies like CuBert, the future of copper solar panels is looking brighter than ever.
In conclusion, the challenges faced by the solar energy industry in using copper solar panels have not stopped researchers and scientists from pursuing their development. The recent success of SunDrive and other companies like PV2+ and Bert Thin Films shows that the dream of making solar energy affordable and accessible to everyone is becoming a reality. As more research and development is done, the use of copper in solar panels will undoubtedly become more efficient and reliable.
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