As of today, organic solar cells can achieve an efficiency level of 12% in terms of converting sunlight into available electricity, this is compared to a double efficiency level of 25-20% in silicon-based cells. Now, researchers have discovered that controlling the spin of the electrons in these cells significantly improves their performance,
Organic solar cells, a new family of solar cells that mimic the natural process carried out in green plants, photosynthesis, may bring about a revolution in the field of renewable energy, provided they can be economically more competitive compared to commercial silicon cells currently used in this market.
Currently, organic solar cells can achieve an efficiency level of 12% in terms of converting sunlight into available electricity, compared to a double efficiency level of 25-20% in silicon-based cells. Now, researchers have discovered that controlling the spin of the electrons in these cells significantly improves their performance, achieving an essential breakthrough in the quest to develop cheap and efficient solar energy technologies. The research, carried out by scientists from the Universities of Cambridge and Washington, was published in the prestigious journal Nature.
Organic solar cells mimic the process of photosynthesis using large molecules based on carbon atoms that are able to utilize sunlight, instead of the inorganic semiconductors normally used in commercial solar cells based on silicon. The organic cells can be thin, light-weight and very flexible, and can be developed with the help of printing them with ink, in a similar way to printing newspapers, a process that enables faster and cheaper production than the existing processes in the industry today.
Despite these important advantages, organic solar cells have a serious problem - many scientists, until now, have been hard-pressed to understand why, unexpectedly, some molecules perform extremely well, while others perform extremely poorly.
Researchers from the University of Cambridge have developed laser-based methods in order to trace the movement and interactions between the electrons flowing in these cells. Much to his surprise, the team of scientists discovered that the differences in performance between different materials could be related to the quantum property known as "spin" (electronic spin). Spin is a property of particles related to their angular momentum, where electrons can have two types of spin: spin up and spin down. Electrons inside the solar cells can undergo a recombination process where they lose their energy (the excited state they were in) and "fall" back into a hollow state known as a "hole".
The researchers discovered that by arranging the spins of the electrons in a defined way, they can prevent the loss of energy following the unification process and thereby increase the current received from the cell. "This discovery is very exciting, since we now understand how to utilize the physics of spin in order to improve the efficiency and performance of solar cells, an insight that we did not previously think was possible at all. We expect to soon see new materials and solar cells that take advantage of this innovative mechanism," said Dr. Akshay Rao, principal investigator from the University of Cambridge. The team of researchers believes that the design ideas that will emerge from this research can help close the gap between organic cells and silicon cells, and finally bring them into commercial production. In addition, some of the new insights could be applied in organic light-emitting diodes (organic LEDs), which today constitute a new display technology that is growing at a fast pace and which enables the development of more efficient displays in phones and portable computers as well as in television screens, displays such as a flexible and foldable surface that can be worn on the arm or fingers even .
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