In most industrialized countries, solar panels account for only a quarter to a third of the overall cost of building a solar farm. But there’s more to consider than just the panels themselves. Additional hardware, financing, installation, permitting, and other expenses make up the bulk of the cost. That’s why it’s important to invest in efficient panels that can convert more of the incoming light into electricity.
However, the current cutting-edge silicon panels can only achieve about 25 percent efficiency, and there’s no way to push the material past 29 percent. The specialized, hyper-efficient photovoltaic hardware used in space is much more expensive than these panels.
But there’s hope for a middle ground. Recent reports have shown progress in the development of two-layer perovskite/silicon solar cells with efficiencies well above 30 percent. Although these cells are not yet durable enough for practical use, they offer potential for the future.
Wearing layers
The concept behind two-layer, or tandem, photovoltaic devices is simple. The top layer should absorb high-energy photons and convert them to electricity while remaining transparent to other wavelengths. The layer underneath should absorb lower energy photons. Silicon is a great candidate for the lower layer due to its peak absorption towards the red end of the spectrum. The challenge lies in finding the right material for the top layer.
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Perovskites are a promising option. They are a class of materials that can be made from a wide range of unrelated chemicals, allowing for potentially inexpensive source materials. Additionally, perovskites can be formed from a solution, making it possible to apply a photovoltaic perovskite coating to various surfaces.
However, the main drawback is that many perovskite crystals are not stable and break down over time. While progress has been made in extending their lifespan, manufacturing perovskite panels is not yet feasible.
Another advantage of perovskites is the ability to tune the peak wavelength absorbed by the crystal by carefully selecting the raw materials. This allows for a wavelength that complements silicon. Although there have been demonstrations of tandem perovskite/silicon cells, their efficiencies have not surpassed what silicon can achieve on its own.
Perovskite and silicon solar cells have recently achieved new efficiency records, enabling advanced and efficient solar power generation.
Building on breakthroughs achieved in organic-inorganic hybrid perovskites and traditional solar cells, scientists from the University of Oxford and other institutions have achieved new world records in solar cell efficiency, exceeding 30% in photovoltaic efficiency. The research teams have exceeded their own previously set records by taking two different approaches.
In the first approach, they developed a three-layer, back-contact solar cell of 1 cm2 manufactured in a “conventional” silicon substrate. This cell achieved a photovoltaic efficiency of 30.2%. Scientists then independently confirmed their results through an international program, setting a new world record.
The second approach involved creating a “multi-junction” device that achieved a photovoltaic efficiency of 33.5%. This device was based on a tandem perovskite-silicon solar cell array, in which the perovskite solar cell was placed atop a silicon cell and connected through an interlayer.
The breakthroughs in solar cell efficiency are groundbreaking and provide an opportunity to further advance the technology of solar power generation. Perovskite and silicon solar cells are now only limited by their cost of production and the challenges of making them durable and reliable. With improvements to affordability and robustness, we could be looking at a future in which vast swathes of energy production is based on solar power.
Overall, the achievement of a combined 33.5% efficiency in photovoltaic cells is a major milestone in solar power technology. With additional research and development, perovskite and silicon solar cells may provide us with an advanced and reliable source of clean energy.
