Including excitons in semiconductor solar cell modelling

Excitonic effects are introduced in standard semiconductor device modelling of solar cells. Previous work by the groups of Green and of Zhang is extended here to also include field dependent exciton dissociation in the space charge layer (SCL) of a n+p diode, and exciton surface dissociation or charge transfer at the contact or at the junction. A clear result is that it is possible to apply the standard semiconductor device modelling frame to situations where excitons are dominant. Even when there is only exciton (and no free eh) generation an almost ideal short circuit current can be collected when there is sufficient exciton dissociation, either at an interface, or in the bulk, or in the SCL. The possible application of this model to organic solar cells is briefly explored.