A solar panel, or photovoltaic (PV) module, converts sunlight directly into electricity using semiconductor materials, most commonly silicon. While silicon is the primary component that absorbs light and generates electrons, the module cannot function without a variety of metals. These metallic elements perform the tasks of collecting the generated electrical current, transferring it out of the panel, and providing the structural integrity needed to withstand decades of outdoor exposure. The metals are integral to the panel’s efficiency, durability, and overall performance.
Metals Essential for Electrical Current Collection
The efficiency of a solar panel depends directly on the swift and unimpeded collection of electrons generated by the silicon cells. This task is primarily handled by highly conductive metals, which form a network of contacts and wires throughout the module. The most prevalent metal used for the electrical contacts on the front surface of crystalline silicon cells is silver.
Silver is utilized in a conductive paste that is screen-printed onto the cell to form thin lines, known as fingers and busbars. This metal is chosen because it possesses the highest electrical conductivity of any metal, minimizing energy loss as the current is collected. Furthermore, silver exhibits excellent stability and corrosion resistance, which is necessary for the long lifespan expected of a solar panel. Although silver is expensive, the small amount used is a necessary trade-off for maximizing efficiency.
Copper is another metal that plays a significant role in electrical current transfer, particularly outside the individual solar cell. It is the core material for the internal wiring that connects the cells within the module, as well as the cables leading from the junction box. Copper’s high electrical and thermal conductivity, second only to silver, makes it an excellent choice for efficiently transferring the bulk current away from the cell array. Researchers are also working on methods to replace silver entirely with copper in the cell’s front contacts to reduce manufacturing costs.
Metals Used for Structural Support and Housing
The physical integrity and protection of the fragile solar cells are provided by a housing structure primarily made of metals. Nearly all solar panels feature a frame made from aluminum, which encircles the glass and silicon layers. Aluminum is highly valued in this application for its low density, making the overall module lighter for transportation and installation, especially on rooftops.
This metal naturally resists corrosion by forming a protective oxide layer when exposed to air, ensuring the frame remains robust over the panel’s 25-year service life. The frame protects the glass and internal components from mechanical stress, such as wind, snow loads, and handling during installation. Aluminum’s malleability also allows it to be easily extruded into the complex profiles required for mounting systems.
For the larger mounting systems that hold the panels in place, especially in large ground-mounted arrays, steel is frequently incorporated. Steel offers superior strength and load-bearing capacity compared to aluminum, which is beneficial in regions prone to high winds or heavy snow. To prevent rust, steel is typically galvanized or coated to ensure long-term resistance to environmental degradation. The choice between aluminum and steel for the supporting racks often depends on the specific project’s scale, location, and required structural strength.
Trace Metals in Semiconductor Layers and Thin Film Technology
Beyond the structural and conductive metals, specific elements are incorporated into the semiconductor material itself to create the photovoltaic effect. In standard crystalline silicon cells, elements like Boron and Phosphorus are introduced as dopants to establish the p-n junction that drives the current. Although these elements are metalloids, they are intentionally added to the silicon to alter its electrical properties, with boron creating the p-type layer and phosphorus the n-type layer.
Alternative solar technologies, known as thin-film panels, rely on entirely different metallic compounds for their active layers, which replace the bulk silicon wafer. One prominent thin-film type is Cadmium Telluride (CdTe), where a thin layer of the compound acts as the primary light-absorbing material. Cadmium is a metal, and tellurium is a metalloid, which together form a highly efficient semiconductor that requires significantly less material than crystalline silicon.
Another major thin-film technology is Copper Indium Gallium Selenide, commonly referred to as CIGS. This material is a mixture of four elements, three of which are metals: copper, indium, and gallium, combined with the metalloid selenium. These metallic compounds are deposited in ultra-thin layers, sometimes along with a back contact layer of molybdenum, to create the active photovoltaic component. CIGS cells are noted for their high absorption coefficient, which allows for very thin films and potentially flexible solar panel designs.