Improving photovoltaics by adding extra terminals to extract hot carriers

Abstract

Photovoltaic cells usually have two terminals, one collecting electrons and the other collecting holes. Can more terminals improve such solar cells? Energy-filtering terminals could collect "hot" carriers (electrons or holes not yet relaxed to the band edge), with other terminals for low-energy carriers. When collection is faster than carrier-phonon relaxation, we predict that four-terminal cells have higher power output than optimal two-terminal cells, often 20-40% higher. Similar effects will occur in multi-terminal thermoelectrics exploiting non-equilibrium distributions.

Version 2: Conclusions are unchanged, but they are better justified by new plots (Fig. 4) & a new discussion of a Shockley-Queisser model in the End Matter. [9 pages, 6 figures]