Scientists in the United States have designed a microwire solar cell that is said to make the link of Singlet -Plending with silicon possible. The key to their performance was an interface that transfers the electrons and holes in succession in silicon instead of both at the same time.
Working with an effect that is known as Singlet Exciton Fission (SF), scientists from the Massachusetts Institute of Technology (MIT) have demonstrated a new silicon solar cell concept that possibly the quantity efficiency limit for conventional PV devices could surpass.
Singlet Exciton splitting is an effect that is seen in certain materials where a single photon can generate two electron hole pairs because it is included in a solar cell instead of the usual. The effect was already observed by scientists in the 1970s and although it has become an important research area for some of the world’s leading institutions in the past decade; Translating the effect into a viable solar cell has proved to be complex.
Singlet -splitting solar cells can produce two electrons from one photon, making the cell more efficient. This is done via a quantum mechanical process in which one single exciton (an electron hole pair) is split into two triplet excitons.
“Until now we have only had indirect evidence that is possible to link Singlet Exciton Splitting to Silicon,” said the corresponding author of the research, Marc A. Baldo, said PV -Magazine. “The breakthrough for us was to design an interface that transmits the electrons and holes successively in silicon instead of both at the same time.”
In the study “Exciton splitting improved silicon solar cell“Which was recently published in Joulethe researchers explained that they have one Microwire (MW) Cell with an interface based on a Hafnium Oxy-Nitride (HFOXNY) Film to improve the link between Tetracene (TC) and Silicon. TC and his derivatives are excellent candidates for SF, because they can form charge transfer and multi-excitonic states.
The interface also included a thin aluminum oxide (ALOX) Passifying layer that prevents the transferred cargo carriers from immediately recumbing to the silicon surface, as well as a zinc falocyanin (ZNPC) layer as an electronic donor material. “To minimize recombination at the rear, a back surface field (BSF) layer with a junction depth of 1 urn and a localized back contact is added,” the scientists said. “A Microgrid electrode is applied as the front electrode to collect carriers efficiently.”
In 2023, researchers from MIT and the University of Virginia announced plans to use ACENEs, which are benzene molecules with unique Opto -electronic properties, in Singlet -splitting solar cells. Their approach consisted of adding carbodicarbenes to acenes that had already been doped with drill and nitrogen.
In 2019, another MIT research group demonstrated how Singlet Exciton splitting could be applied to silicon solar cells and could lead to cell efficiency as high as 35%. They claimed to be the first group to convey the effect of one of the ‘excitonic’ materials that are known to show it, in that case also tetracen. They achieved the performance by placing an extra layer, only a few atoms thick from hafnium oxynitride between the silicon solar cell and the excitonic tetracen layer.
The MIT researchers described their work as “turbo -charging” silicon solar cells and said it differs from the most common approaches to increase the efficiency of solar cells, which are now more focused on tandem cell concepts. “We add more power to the silicon in contrast to making two cells,” they said at the time.
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