Breakthrough in Lightweight and Affordable Solar Cells
Breakthrough in solar energy: New solar cells could soon be stuck to facades like wallpaper or even onto clothing. Researchers at Cambridge University have now proven the functionality in the laboratory for the first time. Photo: Unsplash
Researchers at Cambridge University have achieved a breakthrough in solar energy. They have found a simpler way to generate electricity from sunlight, using materials that hardly anyone had previously considered for this purpose.
What they have discovered could change the future of solar energy: solar cells made from just a single material that are lightweight, inexpensive to manufacture, and highly efficient.
The Difference from Conventional Solar Cells
When sunlight hits a solar cell, electrons are set in motion. These electrons are tiny, negatively charged particles in atoms. When they move, electrical current is generated that we can use.
Classic solar cells, like those seen on many roofs, consist of multiple materials. In these solar panels, one material typically donates electrons while a second one accepts them. The current flow occurs at the boundary between these two layers. This interface is technically tricky, expensive to manufacture, and limits the cell's efficiency.
Researchers have therefore long dreamed of building solar cells that work without this complicated material boundary. A cell that does everything in one: absorb light, move electrons, and generate electricity. Many teams have failed at this because it normally doesn't work with organic materials.
Organic materials are carbon-based molecules, similar to plastics or dyes. They are lightweight, flexible, and often inexpensive to manufacture, unlike inorganic crystals such as silicon.
P3TTM: A Molecule with a Special Trick
The Cambridge team has now studied an organic material with an unwieldy name: P3TTM. This material belongs to a group called "radical organic semiconductors." Each molecule has an unpaired electron that is particularly reactive. It can be set in motion when light falls on the material.
In their study, the researchers have now discovered that when these molecules lie close together, they influence each other, to put it simply. The electrons naturally move from atom to atom. This behavior was previously only known in materials like metals or crystals, but not in this way in organic materials like P3TTM.
And this discovery is groundbreaking. When light now hits the material, an electron jumps from one molecule to the next and current flows.
Solar Cell Still Needs External Power
This is the first discovery of an organic solar cell that can generate electricity from just one material. Previously, the rule was: organic solar cells need at least two materials, each performing a different task. One donates electrons, the other captures them. This combination was always a bottleneck because energy is lost at the boundary between the two materials.
In the new solar cell, almost every absorbed light particle was directly converted into electrical current in an experiment. The yield was therefore very high. This could at least be demonstrated in principle, with one significant limitation.
This laboratory breakthrough only succeeded with applied voltage. External energy was therefore needed to achieve the high efficiency. Otherwise, without external voltage, the yield was rather small. However, the researchers led by study leader Biwen Li emphasize that their experiment provides the "proof of concept". That is, proof that the principle works.
Now the material must be optimized so that the yield remains high even without external energy. The cell is therefore not yet ready for practical use, but the research shows that developing such a material is possible.
A Piece of Quantum Magic from Sir Nevill Mott
The research leaders connect their discovery with old theories and ideas from physicist Sir Nevill Mott. Mott had researched how electrons influence each other in dense materials roughly 100 years ago. These interactions are incredibly small and follow the rules of quantum mechanics - the physics of the tiny.
This old theory describes exactly the behavior of the new material. In P3TTM, the electrons don't stand still but influence each other. When light hits them, they begin moving, and this movement can be directly converted into electricity. "It's as if the electrons suddenly hold hands and dance together," describes lead researcher Richard Friend.
Friend had worked with Nevill Mott in his younger years. In a statement, he now speaks of how this closes a circle for him. According to Friend, Mott would have been very pleased to see his theories about electron movement now coming alive in completely new materials. And not just for science, but for everyday life.
The Goal: Affordable Solar Cells Like Wallpaper
Solar energy is currently one of the best tools against climate change, but it also has limitations: cell manufacturing is expensive, they require rare materials, and recycling is difficult. If organic solar cells now achieve the same or higher efficiency but consist of simple and inexpensive substances, the price of solar energy could drop significantly.
This would make electricity more affordable for everyone, even in areas where conventional cells have barely been used so far. Ultra-lightweight, flexible films are conceivable that can be applied everywhere like wallpaper: on windows, building facades, tents, or even clothing. Everything that captures light could provide electricity. The material could also enable a leap forward in space travel.
A Long Road, but Clear Progress
This is still music of the future. The Cambridge team has only shown for now that the idea works in principle. However, it's still a long way from the laboratory to mass production. In addition to further material development, the cells must then also prove themselves in everyday use. They must withstand sun, wind, and rain. Questions about production, environmental impact, lifespan, and recycling must also be clarified.
If all this succeeds, it would be an enormous step for solar energy. Professor Hugo Bronstein, who co-developed the molecules, speaks of a new chapter in the textbook. Because until now it was considered certain that organic materials cannot achieve charge separation without a partner. Now it turns out: yes, they can. And if such solar wallpapers could one day be applied simply and cheaply to all roofs and facades, that would be a small revolution in energy supply.
Sources
Nature Materials: Intrinsic intermolecular photoinduced charge separation in organic radical semiconductors
University of Cambridge: New organic molecule set to transform solar energy harvesting
Science Daily: Scientists unlock a 100-year-old quantum secret to supercharge solar power
Nature: A new kind of solar cell is coming: is it the future of green energy?
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