Probing the pathways of free charge generation and recombination in organic solar cells : the role of excess energy and dispersive effects Organic semiconductors are a promising class of materials. Their special properties are the particularly good absorption low weight and easy processing into thin films. Therefore intense research has been devoted to the realization of thin film organic solar cells (OPVs). Because of the low dielectric constant of organic semiconductors primary excitations (excitons) are strongly bound and a type II heterojunction needs to be introduced to split these excitations into free charges. Therefore most organic solar cells consist of at least an electron donor and electron acceptor material. For such donor acceptor systems mainly three states are relevant; the photoexcited exciton on the donor or acceptor material the charge transfer state at the donor acceptor interface and the charge separated state of a free electron and hole. The interplay between these states significantly determines the efficiency of organic solar cells. Due to the high absorption and the low charge carrier mobilities the active layers are usually thin but also …