Influence of the recombination mechanism via band tails on the electric performance of a bulk heterojunction solar cell

Trap assisted recombination via tail states model was simulated and the results were compared with those obtained from direct recombination model. It is shown that the dark ideality factor of the first one depends directly on both the Urbach energies and charge carrier capture coefficients. These parameters were directly related to the loss of efficiency in organic solar cells. When either one of capture coefficients or Urbach energies increase, the density of traps increases as well, and solar cell ideality factor deviates from 1 to 2. On the contrary, the ideality factor is close to unity as long as the density of states is low, in such case the recombination becomes band to band type. Under our assumptions, the dark ideality factor is influenced by trap assisted recombination model and under illumination, solar cell parameters are strongly reduced by trap assisted model via band tails recombination as we will demonstrate in our results.