Photoinduced processes of functionalized perylene bisimides

Abstract

Photoinduced electron transfer at the interface of a donor and acceptor material is the primary step in organic solar cells in which photons are used to create free charge carriers. Because the lifetime and diffusion length of photoexcitations in organic materials is limited, efficient charge separation can only be obtained when the electron donor and acceptor materials are in close, nanometer, proximity. A second requirement for efficient solar cells is that the generated charges can be transported to the two electrodes. Hence, it is important that both materials form a continuous phase, extending from the interface to the electrode. Both conditions can be fulfilled in composites of electron donor and acceptor materials. However, the morphology of these composite organic semiconductors is difficult to control. Often, large domains of the components are formed, which have a small interfacial area precluding efficient charge generation. In contrast, too well mixing provides a large interface but is prone to give discontinuities in the transport pathways, resulting in charge recombination. Creating and maintaining nanoscale bicontinuous order of the two chromophores are therefore important to obtain efficient organic solar cells. A possibly elegant approach to control the morphology of donor and acceptor is by incorporating the two components into block copolymers that are able to provide a predefined bicontinuous nanostructure via self-organization, since the covalent bond between donor and acceptor defines the dimension of the two phases. This thesis describes the synthesis and photophysics of such novel donor-acceptor polymers and related architectures based on electron deficient perylene bisimides and ?primarily? electron rich oligo(p-phenylene vinylene)s.