Most solar panels that cover roofs, fields, and deserts today have the same composition: crystalline silicon. Its raw material is polysilicon, which is processed into wafers and made into photovoltaic cells, which convert sunlight into electricity. But in recent years, the solar industry's dependence on this single technology is becoming a burden, and supply chain bottlenecks are slowing the global deployment of new solar installations.
Fortunately, crystalline silicon is not the only material that can use solar energy. In the United States and China[China's commercial production of cadmium telluride thin film power generation glass has a conversion efficiency of 15.8%], scientists and manufacturers are working to expand the production of cadmium telluride solar technology. Cadmium telluride is a kind of "thin film" solar cell. As the name suggests, it is much thinner than traditional silicon cells. Today, panels using cadmium telluride supply about 40% of the U.S. utility-scale market and about 5% of the global solar market.
Energy consulting company Wood Mackenzie pointed out that the photovoltaic industry has entered a very unstable period, especially for the crystalline silicon supply chain. In the coming year, cadmium telluride manufacturers have great potential to occupy more market shares.
In June of this year, American solar manufacturer First Solar said it would invest US$680 million to build a third cadmium telluride solar plant in northwest Ohio. After the facility is completed in 2025, the company will be able to produce 6 GW of solar panels. This is enough to power approximately 1 million American homes. Another Toledo solar company based in Ohio recently entered the market and is producing cadmium telluride panels for residential roofs. The U.S. Department of Energy and its National Renewable Energy Laboratory (NREL) have launched a US$20 million program to accelerate the development of cadmium telluride research and supply chain. The goal is to help the U.S. solar market develop from the global supply chain. Limit.
Researchers from NREL and First Solar have been collaborating to develop cadmium telluride technology since the early 1990s. Cadmium and tellurium are by-products of smelting zinc ore and refined copper, respectively. Silicon wafers are connected together to make a battery, and cadmium and tellurium are used as a thin layer of material—about one-tenth the diameter of a human hair—and applied to the glass along with other conductive materials. First Solar is currently the world's largest thin film manufacturer, exporting thin film battery modules to 45 countries.
NREL scientist Lorelle Mansfield (Lorelle Mansfield) said that the technology has certain advantages over crystalline silicon. For example, thin film processes require less material than wafer-based methods. Thin film technology is also very suitable for flexible panels, such as panels covering backpacks or drones, or panels integrated into building exterior walls and windows. The important thing is that thin-film panels perform better at high temperatures, while silicon panels may overheat and cause low power generation efficiency.
But crystalline silicon has the upper hand in other areas, such as their higher average efficiency (the percentage of sunlight that solar panels absorb and convert into electricity). Historically, the efficiency of silicon panels is higher than that of cadmium telluride technology, but the gap is narrowing. The efficiency of today's industrially produced silicon panels can reach 18% to 22%, and First Solar reports that the average efficiency of its latest commercial panels is 18%.
However, the main reason silicon dominates the global market is relatively simple: it all comes down to cost. The cost of producing crystalline silicon per watt of solar energy is about US$0.24 to US$0.25, which is lower than other technology paths. First Solar said that it no longer reports the cost per watt of producing cadmium telluride panels, but that the cost has been "substantially reduced" since 2015 (the company reported a cost of $0.46 per watt at the time), and it is falling every year. Polysilicon raw materials are also used in computers and smart phones, and are more widely available than cadmium and tellurium, and the price is lower. With the expansion of silicon panel and related component factories, the total cost of manufacturing and installing this technology has fallen. At present, about 80% of the world's crystalline silicon manufacturing supply chain is in China.
As the manufacturing industry expands, the cost per watt of cadmium telluride and other thin film technologies is also expected to drop. First Solar said that when its new production line facility in Ohio opens, the company will provide the lowest cost per watt in the entire solar market. But cost is not the only important indicator. The current supply chain problems facing the solar industry show this.
First Solar CEO Mark Widmar (Mark Widmar) said that the company plans to spend 680 million US dollars to expand, which is to establish a self-sufficient supply chain and make the US solar industry "decouple" from China. Part of the big effort. The company's existing solar panel recycling program allows it to reuse materials multiple times, further reducing its dependence on foreign supply chains and raw materials.
Scientists at First Solar and NREL continue to test and improve the cadmium telluride technology and collaborated to develop a new method of "doping" thin film materials with copper and chlorine to achieve higher efficiency. NREL announced the results of a 25-year field test conducted at an outdoor facility in Golden, Colorado. A 12-panel array consisting of cadmium telluride panels operates at 88% of its original efficiency, which is consistent with the performance of a silicon system. NREL stated that its goal is not to replace crystalline silicon with cadmium telluride, nor to establish a technology that is superior to another. They all have a place in the market, and they all have their own applications.