While solar panels today provide many benefits, they are barely more than 20 percent efficient. New materials and even artificial intelligence may soon increase output tremendously.

Solar Panel Background

The process for converting sunlight into electrical current was discovered way back in 1839 by French physicist Edmond Becquerel. In 1883, New York inventor Charles Fritts created the first solar cell by coating selenium with a thin layer of gold, though it wasn’t until the 1950s that Bell Labs demonstrated the first modern silicon-based solar cells. (A Brief History of Solar Panels in Smithsonian Magazine) 

Ever since that demonstration, progress to increase solar panel efficiency has been slow.

Solar Panel Efficiency

Most solar panels are between 15 percent and 20 percent efficient, according to Solar Labs, though a few high-efficiency solar panels can exceed 22 percent.  That efficiency number is a measurement of the panel’s capacity to convert sunlight into power. A solar panel with a 20 percent rating, for instance, converts 20 percent of the sun’s energy into solar power.

Photo courtesy of Fire Mountain Solar

Solar panel efficiency is primarily determined by two main factors, the photovoltaic cell efficiency based on the cell design and silicon type, and the total panel efficiency based on the cell layout, configuration and panel size. Cell efficiency is calculated by the fill factor, CER explained, which is the maximum conversion efficiency of a photovoltaic cell at the optimum operating voltage and current.
Cell efficiency is affected by the cell structure and type of substrate used, which is generally either P-type or N-type silicon. The type of material, such as monocrystalline silicon or cadmium telluride, has an influence on how light is converted to electricity, Solar Labs explained. The arrangement of wires and "busbars" that capture and transport power on a solar panel affects efficiency too. Solar panels cannot absorb energy from the entire solar spectrum, so some wavelengths of light that solar panels cannot process bounce back off the panels. A solar panel's efficiency may also be reduced if light is reflected away, which can be affected by the glass layer on top of a solar cell.

The Materials to Produce Solar Panels will Change

After incremental progress for so long, the pace of change has increased rapidly over the past decade and innovations are underway that can make solar panels far more powerful.

One of the most promising innovations is the use of perovskites. Researchers from the University of Washington, University of Toledo, University of Toronto, Northwestern University and Swiss Federal Laboratories for Materials Science and Technology collaborated on improving the durability of perovskite solar cells, according to Science Daily. "Perovskite solar cells offer a route to lowering the cost of solar electricity given their high-power conversion efficiencies and low manufacturing cost," said University of Toledo professor Yanfa Yan. The team discovered the ingredient that enhances adhesion and mechanical toughness.

Researchers at Purdue University who are also working with perovskite have created multifunctional ligands that improve the charge transfer, power conversion capability and long-term stability of perovskite solar cells. “Our conjugated ligands have a perfect fit into the perovskite crystal lattice and can help build a 2D-on-3D perovskite heterostructure, which further enhances the solar panel’s stability,” researcher Letian Dou said.

Another innovation combines perovskite semiconductors and quantum dot solar cells to make perovskite quantum dot solar cells. Perovskites are salts that form into a novel class of hybrid semiconductors, while quantum dots are nanoscale semiconductors. Whereas commercial solar panels today generate heat at the cost of energy efficiency, perovskite semiconductors and quantum dot solar cells have unique properties that are able to retain more energy as electricity rather than heat. National Renewable Energy Laboratory scientist Joey Luther has found that perovskite/silicon tandem solar cells have up to 32 percent efficiency.

Researchers at Martin Luther University Halle-Wittenberg recently said they discovered a new method to increase the efficiency of solar cells by an incredible factor of 1,000, by creating crystalline layers of barium titanate, strontium titanate, and calcium titanate. While it is still early days and much more information is needed, the announcement shows that researchers are continuing to look for even better solar panels. If the innovations such as this one are possible, they could upend current methods.

Form Factors and Processes will Evolve

Emerging technologies could turn windows into transparent solar cells that generate electricity, CNET reported. A solar window with a transparent coating or material gathers energy from the light passing through the window and stores it as electricity. While transparent solar technology is less efficient than the photovoltaic panels on rooftops, they could power devices adjacent to the window such as electric blinds. Ubiquitous Energy, which is developing solar windows, uses a special glass coating applied during the normal manufacturing process of windows to capture ultraviolet and infrared light energy.

In Italy, the 3SUN Gigafactory is developing bifacial panels which could use both direct sunlight and sunlight reflected from the ground onto the back of the panel. Research is currently focused on tandem cells, which consist of two overlapping cells, one “traditional,” and the other made of perovskite. The panels have an efficiency level of up to 24 percent and a lifespan of up to 35 years.

The World Economic Forum (WEF) reported that researchers from UNSW Sydney and Exciton Science made a breakthrough in infrared technology that could lead to solar panels that work at night. The researchers successfully tested a thermo-radiative diode that converts infrared heat into electricity, using technology similar to that used for night-vision goggles. While the amount of energy produced is currently small compared to solar panels, about 0.001 percent, it shows the possibility of developing solar panels producing energy even at night.

In the UK, a start-up founded by researchers at the University of Exeter is working on converting solar energy to electricity via an innovative solar glass brick which can be incorporated into the fabric of a building. The bricks fit into either new buildings or as part of renovations in existing properties. Intelligent optics can focus incoming solar radiation onto small solar cells, enhancing the energy generated by each solar cell.

Researchers at Stanford University are working on concentrating the amount of light that hits a solar cell and getting the same amount of light to hit an area a third of the size, which could make solar panels more efficient in indirect light conditions.

AI can Improve Efficiency

Along with using new materials and practices, work is underway to use artificial intelligence (AI) to increase efficiency and reduce costs. Key areas include using AI algorithms to optimize the positioning of solar panels and reduce shading, which improves solar energy production, and using AI-based predictive analytics to identify potential issues with solar panels or inverters before they become major problems, which reduces maintenance costs and downtime. AI is also beginning to be used to analyze weather patterns and solar radiation levels to predict future solar energy production, improve energy planning and grid management. AI could then optimize the performance of energy storage systems and manage the performance of solar panels, inverters, and other components of solar power systems.

Impact

While the timing for full deployment of these innovations and their actual impact or timeline are uncertain, it’s clear that major changes are underway in solar technology. Some observers have even said the pace of innovation might be too fast, as solar cells produced today may be obsolete tomorrow. While companies and consumers planning to install solar panels have long had to consider whether to install today or wait, the considerations in making a decision are becoming even more complex given the scale of innovation underway.