  Improving the conversion efficiency of solar energy to electricity is most
important to mankind. For single-junction photovoltaic solar-cells, the
Shockley-Queisser thermodynamic efficiency limit is extensively due to the heat
dissipation, inherently accompanying the quantum process of electro-chemical
potential generation. Concepts such as solar thermo-photovoltaics and
thermo-photonics, have been suggested to harness this wasted heat, yet
efficiencies exceeding the Shockley-Queisser limit have not been demonstrated
due to the challenge of operating at high temperatures. Here, we present a
highly efficient converter based on endothermic photoluminescence, which
operates at relative low temperatures. The thermally induced blue-shifted
photoluminescence of a low-bandgap absorber is coupled to a high-bandgap
photovoltaic cell. The high absorber's photo-current and the high cell's
voltage results in 69% maximal theoretical conversion efficiencies. We
experimentally demonstrate tenfold thermal-enhancement of useful radiation for
the high-bandgap cell and 107% enhancement in average photon energy. This paves
the way for introducing disruptive-innovation in photovoltaics.
