Organic and hybrid photovoltaics devices have emerged as promising, solution processed thin film solar cells. In such devices, the active layer is composed of blend of an electron donor and electron acceptor species mixed on the nano-scale and termed bulk heterojunction (BHJ). When light is absorbed by the donor, an electron is promoted to an excited stated generating an exciton (e-h pair). Excitons at the donor:acceptor interface dissociate into free carriers by electron transfer to the acceptor. The carriers then migrate in the electric filed and along the respective phases, electrons on the acceptor and holes on the donor, to the electrodes. Therefore, the performance of such devices strongly depends on the BHJ morphology which is complex and includes ordered, disordered and mixed domains. The aim of this presentation is to show how electron microscopy techniques are used to characterize the nanostructure morphology of organic and hybrid BHJs and allow a structure-performance correlation. Few example will be demonstrated including: the use of HRSEM EDS to calculate the mass of an inorganic acceptor in the organic donor; EFTEM to determine the size and distribution of all-organic donor and acceptor domains; and HAADF STEM to follow the distribution of organometallic complexes in the BHJ.
