Monte Carlo simulation of transport coefficient in organic solar cells

The Monte Carlo simulation was used to study the charge transport mechanism inside a three-dimensional bulk heterojunction (BHJ) polymer solar cell having an additional layer on the BHJ active layer. In the BHJ section, the P3HT:PCBM ratio was varied and its optimum value, in which the diffusion coefficient reached its maximum value, was determined. The diffusion coefficient and short-circuit current (J sc) were simulated. In low diffusion coefficients, recombination losses limited the performance, which led to a reduction in the short-circuit current. The results showed that adding a P3HT layer having a thickness of 10 nm over the BHJ layer increased hole mobility and enhanced short-circuit current and performance of the solar cells. On the other hand, adding a PCBM layer between the active layer and the cathode side behaved as an efficient hole blocking layer so that electrons could be selectively extracted.