Solar Panel Technology Advances: From Perovskites to Thin-Film

Solar energy is growing amazingly fast. From 2019 through 2022, the total amount of solar capacity in the world nearly doubled. And it’s not hard to see why solar is so popular. Besides being a clean energy source, it’s one of the least expensive ways to generate electricity. It’s actually cheaper to build a whole new solar farm than to keep running an existing coal power plant.

One reason for solar power’s low cost is advances in solar panel technology. In the 1980s, commercial solar panels were only about 10% efficient. That is, they converted about 10% of the sunlight that struck them into electricity. Today’s panels are nearly 25% efficient. That’s a huge gain, but it’s only the beginning of what’s possible for solar. New technologies promise to boost solar efficiency even higher while reducing costs still more.

Solar panel basics

The principle behind solar panels is called the photovoltaic effect. In essence, it means that certain materials produce an electric current when exposed to light. The best materials for this purpose are semiconductors. They transmit current better than insulators, such as wood, but not as well as conductors, such as metal. Most solar panels are made from crystals of a semiconductor called silicon.

When light strikes a photovoltaic (PV) cell, some of its energy transfers to the semiconductor material. If the amount of absorbed energy is big enough, it knocks an electron loose from the material. PV cells have one surface treated to make it more receptive to electrons, so these free electrons migrate toward it. Thin wires connected to both surfaces pick up and direct this electrical current.

Each individual PV cell is tiny, but cells can be wired together to create larger modules, or panels. These, in turn, can link up to form arrays of varying size—anywhere from two PV panels to hundreds. In 2022, solar panels generated 1,310 terawatts (TW) of energy worldwide—about 4.4% of all the world’s electricity. That’s not much, but it’s a more than tenfold increase from just 96 TW ten years earlier.

The growth of solar power has lots of benefits for the environment. Unlike the fossil fuels that provide most of the world’s energy, solar power produces no air pollution. It doesn’t emit the greenhouse gases responsible for climate change. And it requires less water than most energy sources, including many other renewable energy sources.

Another benefit of solar is its low cost, which has fallen dramatically over time. Back in 1980, it cost around $30 to produce one watt of solar energy. By 2010, that had dropped to $2 per watt. And from 2010 through 2020, it fell to a mere $0.02 per watt.

One major limitation of solar energy is the amount of space it requires. A solar farm with traditional silicon panels covers 19 square meters per megawatt (MW) of energy generated. That’s far more space than most energy sources, making solar impractical in heavily developed areas. However, making PV panels more efficient could greatly reduce these land requirements. Today’s solar panels, though much better than yesterday’s, are still less than 25% efficient. Boosting that number to 50% would halve the space needed to produce each MW of electricity. That could help solar energy spread to areas where it’s not useful now.

Advances in solar panel technology

Several factors affect a solar panel’s efficiency. One major factor is the material used and how much light it absorbs. The design of the cell also affects how much sunlight it can capture. In recent years, scientists have discovered ways to tweak both these factors, improving PV cells’ efficiency. They’ve also experimented with solar cell designs that aren’t more efficient, but are cheaper, thinner, lighter, or easier to install.

Multijunction and tandem solar cells

Different types of photovoltaic materials are better at absorbing different wavelengths, or colors, of light. One way to improve a PV cell’s efficiency is to combine different materials that are good at absorbing different wavelengths. The result is known as a multijunction solar cell. The difference in color spectrum between the materials is called the bandgap. The bigger the bandgap is, the bigger the boost in the cell’s efficiency.

Dual-junction solar cells, also known as tandem solar cells, contain two different materials. However, it’s possible to achieve even greater efficiency gains by combining more than two materials in one PV cell. In 2020, scientists tested a six-junction solar cell that could capture a whopping 39% of solar energy in real-world conditions.

The biggest challenge with multijunction solar cells is cost. Most of the materials used to make them cost more than even the highest-quality silicon crystals used today. However, researchers are working on ways to make them with less expensive materials—such as perovskites.

Perovskite solar cells

Perovskites are minerals with a specific type of dense crystalline structure. Some perovskites are semiconductors that create a current when exposed to light. A layer of perovskite material over another layer of charge-carrying material creates a functional solar cell.

The earliest perovskite solar cells, created in 2009, were only about 3% efficient. But through experimentation, scientists gradually boosted their efficiency to rival, and then surpass, silicon PV cells. In 2022 and 2023, several groups of scientists created perovskite-silicon tandem solar cells that were over 30% efficient.

One big benefit of perovskites is their low cost. Not only are the raw materials inexpensive, but they also have a high defect tolerance. In silicon PV cells, crystals must line up perfectly for the cell to function. Any damage makes the cell unusable. But perovskites can simply be layered onto a surface, making manufacturing cheaper and easier.

The biggest limitation of perovskites is their durability. Perovskite cells are small and fragile, and they break down quickly when exposed to heat, moisture, or oxygen. Scientists are working to overcome this problem by combining perovskites with various other materials to improve their stability. In 2022, scientists at Princeton University announced a breakthrough: a perovskite cell that could last up to 30 years.

Other advancements in solar panel efficiency

New materials aren’t the only way to boost solar panel efficiency. Bifacial solar panels are traditional silicon panels configured to capture light on both sides. This allows them to absorb light that reflects off the ground or other materials. Bifacial solar panels cost more to manufacture than traditional one-sided panels. However, they can also capture anywhere from 3% to 27% more energy. This cuts the overall cost required to produce one megawatt-hour (MWh) of electricity by 6% to 23%. And, as a bonus, bifacial solar panels have a longer lifespan.

Bifacial panels can significantly boost energy production for solar farms, especially when coupled with solar trackers that maximize sun exposure. However, they’re not that practical for most homeowners. To allow both sides to get sunlight, the panels require special mounting hardware that adds to the cost of the array. And bifacial panels require more frequent cleaning to function optimally.

Another interesting development is solar panels that work at night. This feat isn’t based on the photovoltaic effect. Instead, it takes advantage of the way the earth loses heat to outer space at night. A device called a thermoelectric generator converts this heat flow to electricity. However, the energy it captures is only a small fraction of what the same panel can produce by absorbing sunlight. At present, this technology exists only in the lab. But with some refinement, it could one day allow solar panels to provide at least some energy 24/7.

Thin-film solar technology

Efficiency isn’t the only way to improve solar panels. For example, thin-film solar panels replace silicon crystals with thin layer of semiconductor spread over a base. Most of these aren’t as efficient as crystalline silicon panels, and they’re generally more expensive. But they have one big advantage: thin-film panels are very lightweight and flexible. This allows them to fit into places crystalline panels can’t, such as curved surfaces. They’re also cheaper to install because they’re lighter and more maneuverable. Thus, even if the panels themselves cost more than crystalline panels, the total cost of an array can be lower.

Several types of semiconductors are used to create thin-film solar panels. Each of these materials has its own set of pros and cons.

• Cadmium telluride (CdTe). This is the most common material for thin-film panels. It’s also the cheapest: around $0.40 per watt. CdTe panels can be up to 22% efficient, not that much worse than crystalline silicon. But they’re challenging to make because they use rare tellurium and toxic cadmium.
• Copper indium gallium selenide (CIGS). CIGS panels are up to 23.4% efficient, a bit better than CdTe panels. They also perform better in low temperatures. However, they’re significantly more expensive at $0.60 per watt. Despite the cost, their high efficiency and low weight make them a popular choice for solar shingles.
• Amorphous silicon (a-Si). Unlike traditional solar panels made from silicon crystals, a-Si panels have thin layers of silicon spread over glass or plastic. Silicon is an abundant and nontoxic material, but panels made this way are only up to 14% efficient. That brings their cost per watt to $0.69.
• Gallium arsenide (GaAs). This is the most efficient material for thin-film panels. GaAs panels can be up to 29% efficient, beating the best silicon panels. However, they’re also extremely expensive—around $50 per watt. They’re mostly used for outer-space applications.

Organic photovoltaics (OPV)

Organic photovoltaics (OPV) is an experimental process that involves replacing the silicon in solar panels with organic materials. Many materials can be used for this purpose, including some that are very abundant and cheap. The process of making the panels is also much simpler. Both these factors have the potential to lower costs significantly.

Another advantage of OPV panels is that they’re extremely thin, flexible, and lightweight. They can be integrated into many kinds of building materials, including transparent materials used for solar windows.

However, OPV solar panels also have major drawbacks. The best ones created so far have been only 18.2% efficient—much lower than silicon panels. And their lifespan is much shorter because organic materials degrade faster when exposed to the environment. Until scientists overcome these problems, OPV solar panels aren’t likely to be commercially viable.

Environmental and economic impact

New technologies have the potential to overcome one of solar energy’s biggest limitations: the amount of land it uses. More efficient tandem cells, perovskites, and dual cells can reduce land requirements by producing more energy per panel. That makes it possible to produce the same amount of energy with fewer panels, occupying less area.

Thin films and OPV panels aren’t any more efficient than silicon—in fact, they’re generally worse. However, they address land use in a different way. These light and flexible panels can be used in locations where other panels can’t. They make it possible to convert existing surfaces—walls, windows, even the bodies of cars—into solar arrays. That means solar energy could be produced in built-up areas, rather than requiring large tracts of open land.

New solar technologies can also bring costs down. Solar panels are already one of the cheapest ways to produce energy—around $31 for 1 MWh of grid-connected solar. (Off-grid solar is cheaper still, at about $23.50 per MWh.) But the cheaper it gets, the more cost-effective it becomes to build solar farms and retire polluting fossil fuel plants.

The solar energy industry is already growing fast. Reducing costs and land use could shoot its growth into overdrive. This would expand the many environmental benefits of solar—its low carbon emissions, pollution, and water use—to more places. And it would speed our transition away from fossil fuels and toward a greener, more sustainable future.

How individuals can support solar energy advances

You may wonder: If solar panels are getting better all the time, should you wait to go solar? Will you save money by waiting for these cheaper, more efficient panels to hit the market?

The answer is almost certainly no. The solar panels available today already offer huge cost saving and environmental benefits. Plus, there are government incentives, such as the federal Investment Tax Credit (ITC), to reduce their up-front cost. However, the ITC and some other incentives are only available for a limited time. So if you’re thinking of installing solar panels, it makes sense to do it as soon as possible. You’ll be able to claim your tax break and also start saving on your electric bill sooner.

If installing your own solar panels isn’t an option for you, you can get the same benefits with community solar. A community solar subscription lets you support clean energy production from a local solar farm, while receiving a discount off your own electricity bill. You don't need to purchase or install rooftop panels, and it's free to join through Perch.

Another way to promote new solar technology is to invest in the solar industry. You can buy stock in companies that manufacture solar panels or in companies that operate solar farms. You can also invest in funds devoted to solar energy or clean energy in general.

One last way to help is by reducing your personal energy consumption. The less energy we all use, the easier it becomes to replace all that energy with clean sources like solar. That will make it easier for society to kick fossil fuels to the curb.

The future of solar panel technology

Solar panels have come an amazingly long way in the past couple of decades. Costs have fallen to just pennies a watt. The solar industry has grown from a fringe technology to a small but significant player in global energy production. And it’s sure to play an even bigger role in the future as the world shifts away from fossil fuels.

New breakthroughs in solar panel technology will make solar even more appealing. Tandem cells, perovskites, and dual cells will improve efficiency, squeezing more power out of each panel. Thin films and OPV will make it possible to install panels in more places. And lower-cost materials like OPV and perovskites will make the solar panels of the future even more cost-effective than today’s.

Solar is one of the keys to building a clean energy future. It’s an essential ingredient for halting climate change and preserving water resources for generations to come. Individuals can be part of this change by going solar now. By increasing demand for solar panels today, we encourage businesses and governments to invest in the solar panels of the future.