Influence of active region thickness on the performance of bulk heterojunction solar cells: electrical modeling and simulation

In the study of bulk heterojunction solar cells based on poly(3-hexylthiophene) (P3HT) and a methanofullerene derivative (PCBM), P3HT/PCBM device performance is strongly depends on the thickness of active region. In such devices, optoelectronic behaviors such as charge carrier generation and recombination, photocurrent generation and charge transport mechanism is different in devices of different thickness. An electrical model accounting for study the influences of active layer thickness on the device performance, is developed to achieve the device parameter for high performance of the polymer–fullerene bulk heterojunction solar cells. In this model, by solving the drift–diffusion equations by considering the boundary condition and uniform potential energy, the effects of the active region thickness on the performance of P3HT/PCBM bulk heterojunction solar cell has been studied. By using this model, we were able to show that the thickness dependence of electrical characteristics is responsible for a reduction of the overall performance of the solar cells. Simulated current–voltage characteristics as a function of active layer thickness reveals relatively good agreement between the model’s predictions and published modeling and experimental reports.