Solar is the cheapest source of energy currently available to the world. It is an abundant resource that is now being used to meet the growing energy needs of people in all parts of the world. However, despite the various advantages of this source of energy, solar energy does not have the most efficient harvesting method.

The highest conversion energy of a solar panel recorded is 22%. Solar panels, which were first invented in 1954, have not come as far as one would expect. However, this 22% conversion efficiency ratio is capable of harvesting much more power than any other energy source. This is due to the singular manufacturing method of solar panels.

There are a variety of solar panels available on the market: monocrystalline, polycrystalline, PERC, and thin film. However, they are all made from the same material: solar cells. 

Before we understand the manufacturing steps of solar panels, let us look at the five main parts of a solar panel.

Five components of a solar panel

  1. Solar cells: Made out of silicon, these solar cells absorb the light from the sun and convert it into electrical energy used to power our electronics.
  2. Glass: A transparent glass frame is installed on top of the solar cells to protect them from harsh conditions including rain, snow and wind.
  3. EVA: The EVA sheet is installed both above and below the solar cells. The thermal and radiation insulation provided by the sheet ensures that the power generated by the solar cells is not lost.
  4. Back sheet: The back sheet is integrated below the lower EVA sheet (i.e. the side that does not face the sun) and acts as an additional layer of protection for the solar cells. This can be one or more layers of polymeric sheet depending upon the solar panel’s design.
  5. Frame: The final and critical component of the solar panel, the frame protects all components from physical damage. The frames are often made from aluminium or any other metal framework to ensure structural integrity.

In most solar panels, the latter four components are the same. The number of solar cells, their size and their distribution are what affect the efficiency. The final assembly of these solar cells changes according to product specifications and thus, you can see the difference in conversion efficiency from solar manufacturer to solar manufacturer. Therefore, to understand why solar panels vary from one another, understanding how they are made is a must.

How are solar panels made? 

Step 1: Processing of raw materials

Solar cells, the critical component of solar panels, are made of silicon. Commonly known as sand, it is one of the most elements on this earth. While pure silicon is hard to find in nature, it can be purified from the sand. It is estimated that in 2020, 8 million metric tons of pure silicon were made specifically for the manufacturing of solar panels. The process of manufacturing pure silicon is stringent and can be broken down into two broad steps:

  1. Sifting: 

The sand procured for the manufacturing of silicon is sifted first to remove any metallic and plastic debris. Oftentimes, large silicon-rich rocks are selected for the manufacturing of pure silica.

2. Ingot moulding: 

Once the rocks are selected, they undergo reactions at high temperatures to be melted and purified. The final product is a pure silicon ingot that is sold directly to the solar panel manufacturing company.

Step 2: Solar wafer manufacturing

A very critical step in the manufacturing of solar panels, this step involves slicing the silicon ingot into thin wafers. These wafers are often the same thickness as a piece of paper i.e. 0.05 to 0.10 millimeters. Once they are sliced this thin, the quality of the silicon is seen clearly. 100% pure silicon wafers often appear transparent. This is the prime reason why they can be used for energy harvesting.

Step 3: Conversion of a solar wafer to solar cells

Once solar wafers undergo stringent quality checks, they are treated with proprietary chemicals to ensure high quality. The treatment is conducted to increase the electrical capacity of the solar cells. Oftentimes, metal conductors are integrated onto the wafer’s surface to increase the conductivity. This coating ensures higher absorption of light.

The treatment can also be conducted in a high-temperature oven where metal atoms diffuse and adhere to the surface of the wafer. This creates a negative junction that ensures electrical conductivity. When removed from the oven, these solar wafers are called solar cells.

Step 4: Processing

Solar cells require processing before they are integrated into a solar panel. While the processing varies from one solar panel manufacturer to another, they often complete the same processing techniques:

  1. Cutting: The solar cells are cut according to required dimensions based on the design of the solar panel. The solar cells don’t necessarily have to be square.
  2. Polishing: The solar cells are polished to ensure the cell surface is smooth and transparent. Irregular and opaque surfaces often reduce energy efficiency.
  3. Inspections: The final inspection of the solar cells are completed based on the product guidelines. Inspections often include electrical conductivity, transparency, thickness, surface tension, area, etc.

Once the solar cell is approved, it is passed onto the final stage.

Step 5: Assembly

In this final stage, the solar cells are assembled with the four other components mentioned above: EVA sheet, backing, glass and frame. The number of solar cells integrated with each solar panel varies. Solar panels for residential use often have only 48 cells, whereas those for large-scale EPC projects often include 72 solar cells. Electrical connections are also integrated into the assembly. 

Once the assembly is complete, the solar panel undergoes multiple visual inspections and electrical tests to ensure it performs according to the requirement.

This is the simplified manufacturing process followed by most solar panel manufacturing companies. The manufacturing process is tweaked according to the company’s product requirement to ensure proprietary products. However, the process given above is the backbone of the solar product installed in most homes.