Solar panels are categorized into three different generations and differ according to their cost and efficiency. They are categorized as first, second and third generation solar cells. Each generation has a different manufacturing process, different Material composition and has its own advantages and disadvantages.
First-generation solar cells:
These solar cells are manufactured in a fashion like silicon used in the semiconductor industry, involving extremely pure silicon. These types of solar cells are mostly categorized as monocrystalline and Polycrystalline solar cells. The PV market is currently dominated by these first-generation solar panels. Monocrystalline and polycrystalline solar panels essentially perform the same function, i.e., capture sunlight and turn it into electricity. The key difference is the type of silicon structure they use. Monocrystalline solar cells are made from a single crystal of silicon. As a single continuous crystal, the electrons inside the cell can move quite easily generating more current and giving out higher cell efficiency. In the case of polycrystalline solar cells, they are manufactured with a nonregular silicon structure as monocrystalline, then electrons cannot move quite easily which leads to reduced cell efficiency. These first-generation solar cells usually have an atypical thickness of around 170 µm. This is said to decrease even further according to ITRPV. Theoretically, for first-generation solar panels, the thermodynamic efficiency limit for a single junction cell is 33%. Crystalline silicon PV cells have laboratory energy conversion efficiencies of over 25% for single-crystal cells and over 20% for Polycrystalline cells. However, industrially produced solar modules currently achieve efficiencies ranging from 18%–22% under standard test conditions.
Pros and Cons of crystalline solar panels.
- Monocrystalline is best for efficiency and they are of high purity as mentioned before.
- Both monocrystalline and Polycrystalline panels can last up to 25 years due to the stable and inert properties of the silicon.
- The price point is high for monocrystalline panels compared to their other counterpart the Polycrystalline ones.
- Even though Polycrystalline panels are cheaper they are not as efficient as monocrystalline panels. Lower efficiency ranges from 13% to 17% as the silicon has more impurities in it.
Figure 1 : (a,c) Multicrystalline solar cell /panel and (b,d) Monocrystalline solar cell /Panel respectively.
Second-generation solar cells:
These are most frequently thin film solar cells, designs that use minimal materials and cheap manufacturing processes. The most popular materials used for this type are
- copper indium gallium selenide (CIGS) – These cells are made by placing layers of copper, indium, gallium, and diselenide on top of each other. They are high efficiency but one of the biggest disadvantages is the presence of the toxic material cadmium Sulfide which is used as a buffer layer in the cell.
- cadmium telluride (CdTe) – These panels are the most common type of thin-film modules available in the market. After crystalline panels, these are the most widely used type in the world.
- amorphous silicon - (a-Si) solar is the oldest thin-film technology, making it the most well-developed type of thin-film PV tech
Film thickness varies from a few nanometers (nm) to tens of micrometers (µm) much thinner than first-generation solar cells. The cell efficiency is not on par compared to its crystalline counterparts. Typical efficiency in the market currently ranges from 11- 15%. The decrease in efficiency makes up for the easier manufacturing process. These thin film solar panels are lightweight and easy to use and move around. Flexibility and portability are the two most important factors with these kinds of panels. Although they can be installed easily these kinds of solar panels are not best suited for rooftops or large solar farms like monocrystalline or Polycrystalline solar panels. These panels can be installed on the rooftop of buses/RVs to power small appliances. One of the biggest differences between thin film solar panels vs crystalline panels is that in the latter the panels contain either mono/multi crystalline solar cells whereas in the former the entire surface has one whole layer of PV material.
Figure 2 : Second generation thin film solar cell
Third-Generation Solar Cells:
Third-generation solar cells can essentially overcome the theoretical efficiency limit of 33% for single-band gap solar cells like monocrystalline and Polycrystalline solar cells. Common third-generation systems include multi-layer ('tandem') cells made of amorphous silicon or gallium arsenide. Emerging third-generation solar cells include
- A dye-sensitized solar cell, also known as 'Grätzel cell'
- Organic solar cell
- Perovskite solar cell
- ·Quantum dot solar cell
Although these solar cells are still not as efficient as the commercial panels available in the market. Particularly perovskite solar cells have been of intense research and interest lately and research efficiencies have increased up to 20%.
Figure 3 : Organic solar cell
Source: Shutterstock
Table 1 provides the current efficiencies of different commercial PV modules. PV systems can be connected to the utility grid or operated in stand-alone applications. They can also be used in building-integrated systems (BIPV) or be ground-mounted, for example, in large-scale, grid-connected electricity production facilities.
Table 1: List of current efficiencies of different commercial PV modules. Source: IEA
(sc/mc/a- Si ) Single crystalline , multicrystalline, amorphous silicon respectively.
Future trends and prospects
R&D is predicted to continuously progress in improving existing technologies and developing new technologies. It is predicted that a broad range of different PV technologies will be available in the market depending on specific applications. Figure 2 shows the efficiency rates of modules available in the market when it started around 2010 and the emergence of different PV technologies.
Figure 4 : PV technology status and future prospects .
Source : IEA
AE Solar offers a wide range of crystalline solar panels ranging from mono-facial to bifacial to half-cut panels. They provide panels in the efficiency range from 16 – 21 % both mono and Polycrystalline solar panels. You can check out the range of products available on the website below. https://ae-solar.com/products-list/. Ultimately there is no one size fits all solution when it comes to choosing solar panels as mentioned above the kind of panel to be sued will depend upon the application itself.