You’ve probably seen solar panels on rooftops all around your neighborhood, but do you know how they actually work to generate electricity? In this article, we’ll take a look at what a photovoltaic solar cell is – the technology behind a solar panel that makes it possible to create energy from the sun. Specifically, we’ll examine the science of silicon solar cells, the solar cells making up the vast majority of solar panels.
Solar cells: the building blocks of solar panels
A solar panel is made up of six different components, but arguably the most important one is the photovoltaic cell, which actually generates electricity. The conversion of sunlight into electrical energy by a solar cell is called the “photovoltaic effect”, hence why we refer to solar cells as “photovoltaic.”
Solar PV cells generate electricity by absorbing sunlight and using that light energy to create an electrical current. There are many photovoltaic cells within a single solar panel, and the current created by all of the cells together adds up to enough electricity to help power your home. A standard panel used in a rooftop residential system will have 60 cells linked together. Commercial solar installations often use larger panels with 72 or more photovoltaic cells.
Solar cells produce energy in three steps
A solar PV cell works in three general steps:
- Light is absorbed and knocks electrons loose
- Loose electrons flow, creating a current
- The current is captured and transferred to wires
The photovoltaic effect is a complicated process, but these three steps are the basic way that energy from the sun is converted into usable electricity by solar cells in solar panels.
What are the main types of solar cells?
There are two main types of solar cells used today: monocrystalline and polycrystalline. While there are other ways to make solar cells (for example, thin-film cells, organic cells, or perovskites), monocrystalline and polycrystalline solar cells (which are made from the element silicon) are by far the most common residential and commercial options.
Silicon solar cells: monocrystalline and polycrystalline
A monocrystalline solar cell is made from a single crystal of the element silicon. On the other hand, polycrystalline silicon solar cells are made by melting together many shards of silicon crystals. This leads to two key differentiators between mono- and poly- cells. In terms of efficiency, monocrystalline solar cells are generally higher than their polycrystalline counterparts. This is due to the use of a single, aligned crystal of silicon, resulting in an easier flow for the electrons generated through the photovoltaic effect. Polycrystalline cells have shards of silicon aligned in many different directions which makes electricity flow slightly more difficult. However, solar panels made with polycrystalline solar cells are usually less expensive than monocrystalline options. This is because the manufacturing process for a polycrystalline cell is simpler and requires fewer specialized processes.
Thin-film solar cells
Thin-film solar cells are what they sound like: much slimmer, lighter-weight solar cells that are often flexible, while still remaining durable. There are four common materials used to make thin-film solar cells: Cadmium Telluride (CdTe), Amorphous Silicon (a-Si), Copper Indium Gallium Selenide (CIGS), and Gallium Arsenide (GaAs).
Thin-film solar cells are not nearly as popular as traditional crystalline silicon options for residential and commercial installations. Thin-film panels remain behind silicon panels in efficiency, and for most homes and businesses, this means they won’t be able to produce enough electricity from thin-film options. However, companies like First Solar have built entire businesses on producing panels with thin-film solar cells (in their instance, CdTe cells) for primarily large-scale utility or corporate solar installations.
Organic solar cells
Solar panels made with organic solar cells are not commercially viable quite yet, but organic solar panels have many of the same benefits as thin-film panels. The biggest difference-maker for organic solar cells is their composition: while traditional and thin-film solar panels are made from silicon or other similar compounds, organic solar cells are made from carbon-based materials. They’re often referred to as “plastic solar cells” or “polymer solar cells” for this reason.
Organic solar cells are flexible, durable, and can even be made transparent. Heard of solar windows? If they ever become a widespread product, they may very well be built with transparent organic solar cells.
Perovskite solar cells
A “perovskite” is any material that has the same crystal structure as the compound calcium titanium oxide, a semiconducting material much like silicon. Perovskite solar cells use a man-made calcium titanium oxide-based material to create another type of thin-film solar panel.
Like organic solar cells, perovskites are not widely available yet. However, their low production costs and high potential efficiencies make them an intriguing option as the solar industry continues to expand and develop better and better solar production options.
How does a silicon solar cell generate electricity?
Silicon solar cells, through the photovoltaic effect, absorb sunlight and generate flowing electricity. This process varies depending on the type of solar technology, but there are a few steps common across all solar photovoltaic cells.
Step 1: Light is absorbed by the PV cell and knocks electrons loose
First, light strikes a photovoltaic cell and is absorbed by the semiconducting material it is made from (usually silicon). This incoming light energy causes electrons in the silicon to be knocked loose, which will eventually become the solar electricity you can use in your home.
Step 2: Electrons begin to flow, creating an electrical current
There are two layers of silicon used in photovoltaic cells, and each one is specially treated, or “doped”, to create an electric field, meaning one side has a net positive charge and one has a net negative charge. This electric field causes loose electrons to flow in one direction through the solar cell, generating an electrical current.
Step 3: The electrical current is captured and combined with other solar cells
Once an electrical current is generated by loose electrons, metal plates on the sides of each solar cell collect those electrons and transfer them to wires. At this point, electrons can flow as electricity through the wiring to a solar inverter and then throughout your home.
Many photovoltaic cells together produce solar electricity for your home
A photovoltaic cell on its own cannot produce enough usable electricity for more than a small electronic gadget. In order to produce the amount of energy a home might need, solar cells are wired together to create solar panels, which are installed in groups to form a solar energy system. A typical residential solar panel with 60 photovoltaic cells combined might produce anywhere from 220 to over 400 watts of power.
Depending on factors like temperature, hours of sunlight, and electricity use, property owners will need varying amounts of solar panels to produce enough energy. Regardless, installing a solar panel system will likely include several hundred solar photovoltaic cells working together to generate and electrical current. You can use the EnergySage Solar Calculator to get an idea of the savings you might see from a solar panel installation.
Install solar panels today to start generating energy from the sun
Solar photovoltaic cells are the building blocks of solar panels, and any property owner can start generating free electricity from the sun with a solar panel installation. On the EnergySage Solar Marketplace, you can register your property to start receiving solar installation quotes from qualified installers. While all quotes involve solar panels made from photovoltaic cells, panel output can change based on equipment quality. If you are specifically interested in seeing quotes for high-efficiency solar panels, simply leave a note on your profile for installers to see.