What Are Solar Panels Made Of?

If you are purchasing solar panels for your home, you may be wondering how soon the panels will pay for themselves. Knowing what solar panels are made of can actually help you answer this question.

Solar panel materials factor into how much the panels cost and how much energy they can produce. That, in turn, factors into how efficient the panels are at converting sunlight into electricity.

This article will help you understand what solar panels are made of and how the cost and payback time of any solar investment depends on your choice of solar panel.

Parts of a Solar Panel

Solar panels are made of many different components:

• An aluminum frame
• A glass cover
• Two encapsulants providing weather protection
• Photovoltaic (PV) cells
• A backsheet to provide more protection
• A junction box connecting the panel to an electric circuit
• Adhesives and sealants between the parts
• Inverters (only in certain cases)

The key components to pay attention to are the inverters and the photovoltaic cells. Differences in these parts have the greatest effect on the efficiency and cost of your solar investment.

Inverters

An inverter converts the direct current (DC) electricity that solar panels generate into the alternating current (AC) that homes and the electric grid run on. Inverters come in two forms: string inverters and micro-inverters.

String inverters are the more traditional type of inverter and are sold separately from solar panels themselves. A string inverter is a stand-alone box of circuitry that is installed between the array of solar panels and the house's electrical panel. It is less costly but potentially less efficient than a micro-inverter. Just as an entire string of Christmas lights, wired in a series, can go out if one of the bulbs goes out, a string inverter is affected by the output of the weakest solar panel in the array.

Some solar panel manufacturers build micro-inverters directly into the back of each of their panels. The array's micro-inverters run in parallel with each other, just as Christmas lights that run in parallel stay lit even if one bulb goes out. Micro-inverters are thus more efficient, as the electricity they produce is the sum of all the different panels rather than the percentage of the least efficient one. But micro-inverters are also more expensive.

Silicon Solar Cells

The core of a solar panel is the individual photovoltaic (PV) cells that are connected together to generate electricity. About 95% of PV cells manufactured today are made of silicon wafers, the thin slices of silicon that are used as semiconductors in all electronics.

The silicon in those wafers is shaped into crystals with a positive and a negative charge so that energy from the sun gets converted into an electrical current. Those crystals come in two main types—monocrystalline and polycrystalline. You can often tell the difference between the two because monocrystalline panels are black-colored while polycrystalline panels are blue. As with inverters, different PV cells have different efficiencies and different costs.

As their name suggests, monocrystalline silicon wafers have a single crystal structure. By contrast, polycrystalline silicon is made from different fragments of silicon crystals fused together. It is easier for electrons to move around in a single crystal structure than it is for them to move in the more ragged structure of a polycrystalline structure, making monocrystalline wafers more efficient in producing electricity.

On the other hand, it is easier to fuse crystal fragments together than to carefully slice a single crystal structure, meaning monocrystalline cells are more expensive. Again, as with inverters, higher efficiency leads to higher costs.

Newer Solar Cell Technologies

One of the limits of silicon wafers is the maximum efficiency with which silicon can convert sunlight into electricity. In solar panels available today, that efficiency stands at under 27%.

Bifacial solar panels—with solar cells facing both front and back of the panels—are becoming increasingly popular, because they can generate up to 9% more electricity than single-sided panels, but they are better suited for ground-mounted solar arrays rather than for rooftops.

Research is also underway to use new combinations of materials to create more efficient panels and make them commercially available. Perovskites or organic PV cells may reach commercialization soon, while more inventive methods such as artificial photosynthesis show promise but are still in earlier stages of development. Research in the lab continues to produce increasingly efficient PV cells, and bringing that research to market is key to the future of solar technology.

Solar Panel Manufacturing

Quality matters. A highly efficient panel is worth little if the manufacturer uses inferior wiring and a panel catches fire.

The independent Renewable Energy Test Center tests the quality of solar panels from different manufacturers and puts out an annual PV Module Index Report. Its top five performers for “high achievement in manufacturing” for 2022 were (alphabetically): Hanwha Q CELLS, JA Solar, Jinko Solar, LONGi Solar, and Trina Solar.