Theoretical study of exciton migration in polymer-based solar cells

Poster apresentado no "11º Encontro Nacional de Química Física - 11ºENQF", Porto, Portugal, 09-10 maio 2013. ; Organic solar cells (OSC) are one of the most promising green technologies for energy harvesting. In these devices the active layer is composed of an organic blend of two polymers or by low weight molecule and a polymer. In either case, due to the nature of the materials used, especially of the polymer, the blend morphology at nanoscale strongly affects the main optoelectronic processes that govern OSC functioning. Polymer chains tend to twist and bend, forming nanodomains of conjugated segments with different lengths, which can present different orientations relative to each other and the surrounding medium. Atomistic calculations suggest that the nature of these conjugated segments can affect exciton and charge dynamics in the organic bulk. The dependence of the molecular properties of the conjugated segment on its length dictates the energetic disorder inside the organic network, while the distribution of conjugated segments with different lengths and orientations affects the spatial disorder (see Figure 1). In this communication we will unravel the effect of energetic and spatial disorder in polymer-based solar cells functioning, namely on exciton migration, which is a crucial mechanism on the performance of OSC. To perform our study, we developed a multi-scale model that uses, as input parameters, the results obtained from atomistic calculations, and consider the main physical processes that mediate exciton migration. The model presented here, establishes a clear link between polymer morphology at nanoscale and its influence on exciton migration, which is a breakthrough compared to other computational models published in the literature. ; Fundação para a Ciência e Tecnologia (FCT)