In a discovery that could have profound implications for the future energy policy, Columbia scientists have shown that it is possible to produce solar cells that are more efficient than energy cells existing silicon by using a new type of material , a development that could help reduce the consumption of fossil fuels.
The team, led by Xiaoyang Zhu, professor of chemistry at Columbia University, has focused its efforts on a new class of inorganic ingredients of organic solar cells known as hybrid perovskites (HOIPs). Their results, published in the prestigious journal Science also explain why these new materials are much more efficient than traditional solar cells -solving a mystery that is likely to scientists and prompt engineers to start inventing new solar materials with similar properties in the coming years.
“The need for renewable energy has prompted extensive research on solar cell technologies that are economically competitive with fossil fuel burning,” says Zhu. “Among the materials being explored for solar cells last generation, HOIPs have emerged a superstar. So far nobody has been able to explain why they work so well, and how much better we could do. Now we know that it is possible to make solar cells based on HoIP even more efficient than anyone thought possible. ”
Solar cells are what turn sunlight into electricity. Also known as photovoltaic cells, these semiconductors are made most often from thin silicon layers that transmit energy through its structure, making it current.
silicon panels, which currently dominate the market for solar panels, you must have a purity of 99.999 percent and are notoriously fragile and expensive to manufacture. Even a defect, such as microscopic misplaced ions-in is missing or additional crystalline structure can exert a powerful attraction on charges of cells generated when they absorb sunlight, dissipating the charges before they can be transformed into electric current.
Because they do not have to be pristine, HOIPs can be produced on a large scale and at low cost. The Columbia team has been investigating HOIPs since 2014. Their findings could help boost the use of solar energy, a priority in the era of global warming.
Over the past seven years, scientists have managed to increase the efficiency with which HOIPs can convert solar energy into electricity, to 22 percent from 4 percent. By contrast, researchers took more than six decades to create silicon cells and get them to their current level, and so far silicon cells can convert no more than about 25 percent of the sun’s energy into electricity.
This discovery, Zhu said, meant that “scientists have just begun to tap the potential of HOIPs to convert the sun’s energy into electricity.”
The long theorists demonstrated that solar cells maximum silico efficiency could never REACH the percentage of energy from sunlight that could be converted into electricity that we can use, is roughly 33 percent. hundreds of nanoseconds for energized electrons to move from the part of a solar cell that infuses them with the energy of the sun, the part of the cell harvesting energy and converts it into electricity that can ultimately be fed in need a power network. During this migration through the solar cell, electrons energized rapidly dissipate their excess energy. But those calculations assume a specific rate of energy loss. Columbia team found that the rate of energy loss is slowed by more than three orders of magnitude in HOIPs – so it is possible to collect excess electronic energy to increase the efficiency of solar cells.
“We are talking about could double the efficiency of solar cells,” says Prakriti P. Joshi, Ph.D. student in the laboratory of Zhu, who is a co-author on the paper. “That’s very exciting because it opens a big, big field of engineering.” Zhu added, “This shows that we can boost the efficiency of solar cells much higher than many people thought possible.”
After demonstrating this, the team then turned to the next question: what is the molecular structure of HOIPs that gives them their unique properties? How to avoid electron defects? They discovered that the same mechanism that cooling energy of the electrons also protects slows down electrons encountering defects. This “protection” makes HOIPs turn a blind eye to the ubiquitous defects in a material developed from the environment and processing solution temperature, allowing an imperfect material behaves like a perfect semiconductor.
HOIPs contain lead, and are also soluble in water, ie, solar cells could begin to dissolve and release lead into the environment around them, if not carefully protected from the elements.
The explanation of the mysterious mechanisms that HOIPs its remarkable efficiencies, Zhu knew, materials scientists would probably be able to imitate with more environmentally friendly materials.
“Now we can go back and design materials that are environmentally benign and really solve this problem everyone is worried,” says Zhu. “This principle will allow people to begin to design new materials for solar energy.”
Study: Columbia University
Principal investigator: Xiaoyang Zhu, professor of chemistry at Columbia University
study published by: Science
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