Perovskite Solar Cells: Solar Panels Of The Future?
The heat is on to transition to renewable energy like solar. However, many hurdles exist in rapidly transitioning to renewable energy, like
manufacturing limitations, material sourcing, and the required investment. But a new technology, perovskite solar cells, seems very promising and could eventually help the world rapidly scale up solar energy generating capacity.
Solar panels rely on semiconductor material to convert sunlight into electricity. Crystalline silicon (c-Si) has dominated the solar cell market as the primary semiconductor material in solar panels for decades, but it requires an expensive, multi-step manufacturing process that consumes a lot of energy. Thin-film solar uses different semiconductors but usually has low efficiency and does not have a large market share. Although the cost of solar panels has plummeted in recent years, it will be difficult to further reduce manufacturing costs without a scientific breakthrough.
These issues have prompted researchers to explore other semiconductor materials, and metal halide perovskite solar cells (PSC) seem especially promising in creating a low-cost, high-efficiency, and durable alternative to silicon solar cells.
However, major engineering challenges exist to improve their performance, durability, and efficiency as this technology is commercialized by dozens of companies. Ideally, solar cells will have a lifespan of at least 25 – 30 years without significant degradation and be highly efficient in converting sunlight to electricity.
What Are Perovskite Solar Cells?
Perovskites are a family of materials with exceptional compositional flexibility, and manufacturers are using them in memory chips, ultrasound machines, and now even solar cells. Many perovskite materials, including methylammonium lead halide perovskites and all-inorganic cesium lead halide, are inexpensive to produce. Scientists have used perovskite materials to create semiconductors with similar properties as silicon.
The photons in the sunlight hit the perovskite absorbers, freeing electrons and creating movement toward the Hole Transporting Layer. That transports the electrons to the conductor, creating power. The electrons are then collected by the Electron Transporting Layer. Unfortunately, some excited electrons might fill holes as opposed to powering the load in a process known as surface recombination.
One of the significant advantages is the potential simplicity in the manufacturing process because this perovskite-based material can be printed on at low temperatures, creating thinner and lighter solar modules. Researchers are examining how perovskite can be modified to create the ideal electrical, physical, and optical properties for various applications.
One variation of perovskite is perovskite-silicon tandem solar cells, which combine crystalline silicon and a perovskite layer. The c-si substrate harnesses long wavelengths, and the perovskites harness short wavelengths. The perovskite tandem cell architectures feature a wide bandgap and show high-performance characteristics.
In a matter of years, PSCs have increased from 4% to 30% efficiency. Much of the research into PSCs is supported by the National Renewable Energy Laboratory (NREL) and the U.S. Department of Energy Solar Energy Technologies Office.
How Do Perovskite Cells Compare To Photovoltaic Solar Panels?
Currently, about 90% of solar panels use silicon as a semiconductor. However, manufacturers cannot process silicon semiconductors in a solution bath because of potential defects in the crystal structure, which can hinder functionality. Perovskites are very fault-tolerant and can be processed from a solution to make a semiconductor ink coating. Likewise, PSCs are also very lightweight and flexible, which is an attractive quality for many solar power applications, such as drones and car roofs.
Yet, silicon solar cells have proven reliable and have a lifespan of 25 – 30 years. Furthermore, even lower-quality solar panels on the market degrade at about 0.8% annually, so at 20 years, the solar panel still has more than 80% of its original capacity. By contrast, perovskite photovoltaics have significant long-term efficiency and power output issues, but further research can help overcome this.
What Are The Hurdles To Widespread Perovskite Adoption?
PSCs have shortcomings compared to silicon solar cells that need to be addressed to make them more commercially viable than the photovoltaic technology that currently dominates the market. Addressing these issues is critical for perovskite solar cells to reach their full potential.
Durability
It is critical to address the long-term performance issues for PSCs to have the lifespan and durability necessary for commercial viability. Currently, PSCs show a lack of stability under real-world applications due to degradation in ambient conditions and have a lifespan of just 2.5 years. Therefore, researchers are investigating ways to develop stable perovskite solar cells by preventing decomposition and extending their lifespan.
Efficiency
Although the power conversion efficiency of PSC has increased dramatically in recent years, the products need to be durable, stable, and have the potential for large-scale manufacturability. However, continued improvement in perovskite solar technology could create both highly efficient and durable solar cells that outperform silicon-based products.
Manufacturing At Scale
Most of the lab-scale production approaches for PSC are not easy to scale up, and low-cost, high-throughput manufacturing processes are essential to reach their full potential. Developing scalable manufacturing approaches that enable mass production is essential for commercial viability. However, roll-to-roll production is a common approach for manufacturing thin-film solar, and research is needed to determine if it is also practical for PSCs.
Environmental Performance
Lead or other heavy metals are commonly used in making perovskite materials. For example, hybrid perovskite solar cells often have hybrid organic-inorganic lead materials in the active layer. Researchers are examining ways to eliminate the use of heavy metals or at least seal in the lead, reducing the human and eco-toxicity concerns. Addressing such concerns will enable PSC to be more sustainable.
Existing Testing Protocols May Need To Be Redesigned
There is concern in the research community that there are no consistent parameters and standards for conducting tests and that tests may not be accurate for PSC. Therefore, it can be challenging to compare data between tests and properly understand degradation mechanisms. Standardized protocols are needed for assessing and reporting the stability of perovskite solar cells.
What Potential Benefits Do Perovskite Solar Cells Offer?
Although there are many hurdles to overcome for PSC to gain a significant market share, perovskites are a promising material.
Highest recorded efficiency: Whereas the most efficient silicon solar cell technology has a conversion efficiency of 25%, researchers have developed PSCs that exceed 30%. Further innovation in efficient perovskite solar cells is likely because there is extensive research in the area of hybrid organic-inorganic perovskite.
Low cost: Despite not being a mature technology, perovskite films already have low production costs, and improvements will likely lead to further reductions. One key advantage is that they can be manufactured at room temperature, saving energy. Determining the most economical way to manufacture PSCs will further lower costs.
Lightweight: Because they are thinner and lighter than even most thin-film solar, PSCs are practical for more applications, including transportation and aerospace. This can lead to further innovation and solar energy deployment.
Low temperature coefficient: PCVs have a much lower temperature coefficient than monocrystalline and polycrystalline solar cells, so they perform better in hot weather. This is especially attractive in hot climates that commonly reach temperatures above 77° Fahrenheit.
Conclusion: Keep An Eye On Perovskite In Coming Years
Although they aren’t quite ready to take the solar energy market by storm just yet, more scientific breakthroughs are likely. Because there is currently extensive research going into perovskite materials and there have been significant advances in recent years, this trend is likely to continue. PSC may eventually overtake silicon solar cells in the coming years, spurring greater solar energy deployment across the globe.
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