Photovoltaics as a Branch of Opto-electronics:Solar Cells, Heat Engines, Electroluminescent Refrigerators

The photovoltaic cell and the LED are really the reciprocal of one another. The slogan: "A great solar cell has to be a great LED" has led to all the new solar cell efficiency records. Very efficient light emitting diodes (LED's), surprisingly, do actually become cold as they operate, since LED light carries away entropy. This refrigeration requires superb LED efficiency, which is enabled by 2d photonic crystal patterning, for luminescence extraction.