The effect of photonic bandgap materials on the Shockley-Queisser limit

The limiting efficiency of photovoltaic energy conversion was determined by Shockley and Queisser using the theory of detailed balance, which described the balance between absorption and emission of photons. However, when a material is placed on top of a solar cell that modifies the transmission of photons (e. g., a photonic crystal), both the absorption and emission of photons are modified. Here, we show how the addition of a photonic structure can lead to an effective modification of the energy bandgap of the material and can subsequently change its maximum theoretical efficiency. We consider the effect of non-ideal photonic structures and the effect of non-radiative recombination within the cell and find that, with realistic materials, efficiency gains of several percent can be achieved with the addition of photonic structures. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4742983]