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What Are Solar Panels Made From?

Wondering what are solar panels made from?


When light interacts with a photovoltaic (PV) cell, also known as a solar cell, it can either be reflected, absorbed, or pass through the cell. The PV cell is constructed from semiconductor material, which means it conducts electricity better than an insulator but not as well as a good conductor like metal. There are various semiconductor materials used in PV cells that solar panels are made from.


When the semiconductor is exposed to light, it absorbs the energy and transfers it to negatively charged particles called electrons in the material. This additional energy enables the electrons to flow through the material as an electrical current. This current is then extracted through conductive metal contacts (the grid-like lines on a solar cell) and can be utilised to power homes and the electric grid.


The efficiency of a PV cell is the amount of electrical power it produces compared to the energy from the incoming light. This indicates how effectively the cell converts energy from one form to another. The electricity generated by PV cells depends on the characteristics (such as intensity and wavelengths) of the available light and various performance attributes of the cell.


A critical characteristic of PV semiconductors is the bandgap, which determines the wavelengths of light the material can absorb and convert to electrical energy. If the semiconductor's bandgap aligns with the wavelengths of light hitting the PV cell, the cell can efficiently utilise all the available energy.



an image of a solar panel close up


Below, you can learn more about the commonly used semiconductor materials for PV cells:


SILICON


Silicon is the most prevalent semiconductor material in solar cells, accounting for about 95% of the modules sold today. It is also the second most abundant material on Earth (after oxygen) and is widely used in computer chips. Crystalline silicon cells consist of interconnected silicon atoms forming a crystal lattice, which provides an organized structure enhancing the conversion of light into electricity.


Solar cells made from silicon currently offer a combination of high efficiency, low cost, and long lifespan. These modules are expected to last for 25 years or more, still producing over 80% of their original power.


THIN-FILM PHOTOVOLTAICS


Thin-film solar cells are created by depositing one or more thin layers of PV material onto a supporting material like glass, plastic, or metal. The two main types of thin-film PV semiconductors on the market are cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS). Both materials can be deposited directly onto the module surface.


CdTe is the second most common PV material after silicon and can be produced using cost-effective manufacturing processes. While this makes them a budget-friendly alternative, their efficiencies are still not as high as silicon. CIGS cells have promising properties for a PV material and show high efficiencies in the lab, but the complexity of combining four elements makes transitioning to large-scale manufacturing more challenging. Both CdTe and CIGS require more protection than silicon for long-lasting outdoor operation.


PEROVSKITE PHOTOVOLTAICS


Perovskite solar cells are a type of thin-film cell named after their characteristic crystal structure. They consist of layers of materials printed, coated, or vacuum-deposited onto a supporting layer called the substrate. They are generally easy to assemble and can achieve efficiencies comparable to crystalline silicon. In the lab, perovskite solar cell efficiencies have improved at a rapid pace, from 3% in 2009 to over 25% in 2020. To be commercially viable, perovskite PV cells need to become durable enough to withstand 20 years of outdoor exposure, so researchers are working on enhancing their durability and developing cost-effective manufacturing techniques.


ORGANIC PHOTOVOLTAICS


Organic PV (OPV) cells are made of carbon-rich (organic) compounds and can be customised to enhance specific functions of the PV cell, such as bandgap, transparency, or colour. Currently, OPV cells are only about half as efficient as crystalline silicon cells and have shorter operational lifetimes, but they could be less expensive to manufacture in large volumes. They can also be applied to various supporting materials, such as flexible plastic, making them suitable for a wide range of applications.


QUANTUM DOTS


Quantum dot solar cells conduct electricity through tiny particles of different semiconductor materials, only a few nanometers wide, known as quantum dots. Quantum dots offer a new approach to processing semiconductor materials, but creating an electrical connection between them is challenging, so their efficiency is currently limited. However, they are easily adaptable for use in solar cells and can be deposited onto a substrate using various methods.


Quantum dots come in different sizes, and their bandgap can be customised, enabling them to capture light that is typically challenging to collect. They can also be paired with other semiconductors, like perovskites, to optimize the performance of a multijunction solar cell.


MULTIJUNCTION PHOTOVOLTAICS


Another method to enhance PV cell efficiency involves layering multiple semiconductors to create multijunction solar cells. These cells consist of stacks of different semiconductor materials, as opposed to single-junction cells, which have only one semiconductor. Each layer has a different bandgap, allowing them to absorb different parts of the solar spectrum and make more efficient use of sunlight than single-junction cells. Multijunction solar cells can achieve record efficiency levels because any light not absorbed by the first semiconductor layer is captured by a layer beneath it.


While all solar cells with more than one bandgap are considered multijunction, those with exactly two bandgaps are called tandem solar cells. Multijunction solar cells that combine semiconductors from columns III and V in the periodic table are known as multijunction III-V solar cells.


Multijunction solar cells have demonstrated efficiencies greater than 45%, but they are expensive and challenging to manufacture, so they are primarily used in space exploration. The military utilises III-V solar cells in drones, and researchers are exploring other applications where high efficiency is crucial.


CONCENTRATION PHOTOVOLTAICS


Concentration PV (CPV) focuses sunlight onto a solar cell using a mirror or lens. By concentrating sunlight onto a small area, less PV material is needed. PV materials become more efficient as the light becomes more concentrated, resulting in the highest overall efficiencies with CPV cells and modules. However, this approach requires more expensive materials, manufacturing techniques, and the ability to track the movement of the sun, making it challenging to demonstrate a cost advantage over today's high-volume silicon modules.

Solar panels, an essential component of solar energy systems, incorporate not only photovoltaic cells but also several key structural elements, most notably metal frames. These frames play a crucial role in the overall functionality and durability of the solar panels. Here's a more detailed look at these components:


Solar Panel Frames


Racking Components


The racking system is fundamental to the installation of solar panels. It provides the structural support necessary to hold the panels in place, either on rooftops or in large-scale solar farms. The design of these racking systems varies depending on the installation location and the type of solar panels used. They must be robust enough to withstand environmental factors like wind, rain, and snow loads.


Brackets


Brackets are an integral part of the mounting system, connecting the solar panels to the racking components. They ensure that the panels are securely fastened and properly aligned. The durability of these brackets is vital, as they must endure various weather conditions over many years. They are typically made from high-strength, corrosion-resistant materials such as aluminium or stainless steel.


Reflector Shapes


In some solar panel setups, particularly in concentrated solar power (CSP) systems, reflector shapes play a significant role. These reflectors are designed to focus sunlight onto a smaller area, typically where a photovoltaic cell or a heat collection element is located. The efficiency of these systems heavily depends on the precision of the reflector shapes, which are usually parabolic or other specifically engineered forms.


Troughs


In certain types of solar energy systems, troughs are used to concentrate sunlight. These trough-shaped reflectors are particularly common in CSP installations, where they focus sunlight onto a pipe running along the focal point of the trough. The concentrated light heats a fluid inside the pipe, which is then used to generate steam and produce electricity through a turbine.


These metal components are critical for the efficiency and longevity of solar panels. They not only provide structural integrity but also enhance the effectiveness of the solar energy collection process. The design and material choice for these components are heavily influenced by the specific application, environmental considerations, and the need for durability and maintenance ease. As solar technology evolves, these components are continually being refined to improve the overall efficiency and sustainability of solar energy systems.

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