Influence of optical interference and carrier lifetime on the short circuit current density of organic bulk heterojunction solar cells

Based on simple analytical equations, short circuit current density (J(SC)) of the organic bulk heterojunction solar cells has been calculated. It is found that the optical interference effect plays a very important role in the determination of J(SC); and obvious oscillatory behaviour of J(SC) was observed as a function of thickness. At the same time, the influence of the carrier lifetime on J(SC) also cannot be neglected. When the carrier lifetime is relatively short, J(SC) only increases at the initial stage and then decreases rapidly with the increase of active layer thickness. However, for a relatively long carrier lifetime, the exciton dissociation probability must be considered, and J(SC) behaves wave-like with the increase of active layer thickness. The validity of this model is confirmed by the experimental results.