In any conventional silicon-based solar cell, there is an absolute limit on overall efficiency, based partly on the fact that each photon of light can only knock loose a single electron, even if that photon carried twice the energy needed to do so.
In any conventional silicon-based solar cell, there is an absolute limit on overall efficiency, based partly on the fact that each photon of light can only knock loose a single electron, even if that photon carried twice the energy needed to do so. But now, researchers have demonstrated a method for getting high-energy photons striking silicon to kick out two electrons instead of one, opening the door for a new kind of solar cell with greater efficiency than was thought possible.
While conventional silicon cells have an absolute theoretical maximum efficiency of about 29.1 percent conversion of solar energy, the new approach, developed over the last several years by researchers at MIT and elsewhere, could bust through that limit, potentially adding several percentage points to that maximum output. The results are described today in the journal Nature, in a paper by graduate student Markus Einzinger, professor of chemistry Moungi Bawendi, professor of electrical engineering and computer science Marc Baldo, and eight others at MIT and at Princeton University.
The basic concept behind this new technology has been known for decades, and the first demonstration that the principle could work was carried out by some members of this team six years ago. But actually translating the method into a full, operational silicon solar cell took years of hard work, Baldo says.
That initial demonstration “was a good test platform” to show that the idea could work, explains Daniel Congreve PhD ’15, an alumnus now at the Rowland Institute at Harvard, who was the lead author in that prior report and is a co-author of the new paper. Now, with the new results, “we’ve done what we set out to do” in that project, he says.
Read more at Massachusetts Institute of Technology