Why Third Generation Solar Cells?
Though the sun’s spectrum is great for putting some color into rainbows, it makes trouble for a conventional solar cell’s efficiency (how much of the sun’s energy it converts to useful electricity). The problem is that light of any color of the rainbow contains energy, but conventional solar cells convert light to electricity best at only one particular color. This color corresponds to some photon energy E0. For photons with E < E0, no light is absorbed by the cell, and for E > E0, light is absorbed, but more and more of its energy is wasted as heat as E increases. This limits the efficiency of conventional cells to a maximum of about 33% in perfect environmental conditions. This ‘conventional’ limit applies to both first and second generation cells. However, third generation solar cell designs are able to overcome this limit using ‘multiple energy threshold’ processes. A number of such processes have been conceived and these will be explored in the talk.