In order to understand how a solar panel works, it’s important to know what a panel is made from. When discussing photovoltaics (another word for solar panels), the vast majority of panels are made from silicon.

It’s one of the most abundant substances available for use. Silicon dioxide goes through several different processes before it’s manufactured into usable silicon. Also, it’s been used in technology for several decades, so it’s a well-understood material.

How is a Solar Panel Made?

After silicon is gathered, it’s heated inside of a large vat. A silicon “seed” is dipped into the molten silicon and is slowly drawn out. The result is a silicon ingot, a cylinder of 99.9% pure silicon. This is called the Czochralski process.

Very thin wafers of silicon are cut from the ingot and then carried off to where they go through the doping process which establishes what’s called the p/n junction, a very important step in the process of converting light into usable energy.

How Do Solar Cells Work?

The p/n junction is the “magic process” for solar panels. Solar cells operate with what’s known as the bandgap, which is a difference in energy between two atomic energy bands known as the conduction band and the valence band. The gap size, measured in electron volts, determines the conductivity of the material. At 3eV, the material in question functions as a fantastic insulator since electrons do not have enough energy to jump the bandgap. If there is no band gap, meaning the conduction and valence bands overlap, the material works as a fantastic conductor.

Silicon is a semiconductor, so it falls somewhere in the middle. The bandgap measurement for silicon is 1.11 eV, so valence electrons, given enough energy, can pass through the bandgap with the help of photons, or units of light. When photons strike silicon, free electrons jump from the valence band to the conduction band where they are transferred to DC power.

Kinds of Solar Cells

Currently, the best solar cells are manufactured from monocrystalline silicon. There are many other technologies that are used in solar cell manufacturing. But why this specific kind? Here are a few other technologies used in solar cell production that don’t make the cut.

• Copper, Indium, Gallium, Selenium - CIGS for short - is a newer technology that operates on thin-film wafers. Although research with CIGS is heavy, there are a lot of toxicity concerns with Indium and other substances used in manufacturing.

• Polycrystalline Silicon - Solar cells are often made from multiple crystals of silicon (thus poly) which is a less time-intensive process and thus cheaper to manufacture. However, poly panels are rated less efficient than their mono counterparts and produce less energy.

• Thin-film - These are more popular for residential applications since they’re easy to transport and are more ideal for roofs because of wider surface area and irregular roof shapes. They’re not very fit for solar lighting applications. 

• CdTe - Cadmium Telluride cells are generally cheaper than their silicon brethren, but at a cost: they’re about 10% efficient, much less than silicon. In addition, Cadmium is also a highly toxic metal. It’s stable when combined with Telluride within a solar cell, but there are environmental considerations with these panels since Cadmium is a known carcinogen found in cigarette smoke.

• Perovskite - In addition to being a toxic chemical, cells manufactured with this material tend to have a very short lifespan, too short to justify a return on investment. Commercialization of cells from perovskite is also very far off.

The reason why mono-Si solar cells are still the best choice on the market is because of their long lifespan (25 years), high efficiency (25% maximum in lab results), and suitable panel sizing for commercial projects. Solar cells that need large array sizes don’t work well simply because the panels are too large for proper wind resistance. Silicon is a well-researched substance for electronics since it’s used in microprocessor production. Also, it’s comparatively less toxic than Cadmium or Indium. 

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3 Tips to Pick Quality Solar Panel from the Manufacturer

If you don’t have quality panels, you’ll lose significant ROI on your projects. Low-quality panels degrade over time for different reasons:

• Microcracks - small cracks in the silicon wafers from poor-quality silicon

• Thermal cycling - heat and cold causes material to expand and shrink, thus warping panels over time

• Humidity -  can potentially destroy the glue holding the cells to the panels

• Potential Induced Degradation  - when electrons tend to behave erratically because of panel age and use

• UV Damage - cheap glue doesn’t have proper UV blockers which can cause the panels to fall apart

• Freezing - If your panels aren’t IP68, water can get inside the glass, freeze, and cause expansion, leading to further damage

Here are 3 things to do and look for when browsing manufacturers for the right type of solar light.

1. As before, Look for manufacturers that utilize monocrystalline panels. Otherwise, you may be purchasing risky materials that won’t last long or won’t provide enough power for your lights.

2. Ensure your manufacturer has a selection process for panels with qualified engineers that know what to look for in components. Not all panels made are of quality, and if you find a company that is picky about which panels they use, that’s usually a strong sign.

3. Some common materials to ask about in the selection process include: 

• Glue - if cheap glue is used to adhere the panel, it could wear off over time and cause damage 

• Backing Material - a quality back sheet protects the panel from UV radiation, temperature fluctuations, and moisture.

• Quality and Thickness of Glass - you’ll want a glass thickness of 3 to 4 millimeters to enhance transmissivity, reduce reflection, and increase strength. Bad (smooth) solar panel glass can cause delamination. Look for panels that use tempered glass. Also, be sure to check if the panels have IEC and UL1307 certificates.

• Wafer Etching - a quality, wet-chemical wafer etch turns solar panels black to absorb more than 98% of direct sunlight. This is a process invented by NREL.

• Panel Bracket - ask how strong the anodization process is for the bracket. Also, avoid brackets that have closed-in cavities and sharp edges.

Adhering to these guidelines will ensure that the manufacturer and their products will deliver the best return on investment and last a long time.

Greenshine New Energy is a solar lighting company that develops and manufactures industry-leading solar-powered lighting systems. We utilize monocrystalline silicon to provide the highest efficiency on our solar panels. Solar lighting is a cost-effective solution for commercial, residential, and industrial projects. Contact our engineers today to find out more about solar panels you can use for your projects.