Monitoring morphology in organic photovoltaic blend systems
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Solution processed organic solar cells based on a bulk-heterojunction morphology have attracted attention as a promising source of energy, featuring materials that can be integrated into devices with the potential for scalable production at low cost. This dissertation discusses the processing of blends of conjugated polymers and discrete molecules, which are typically electron donating and accepting materials, respectively, for thin-film photovoltaic applications. Critical to the performance of the blend film is the nano- and micro-scale morphology, which is dictated by inter- and intra-molecular interactions among the blend components. This morphology can be controlled during the solution processing step, which is the focus of this dissertation. Traditionally, spin-coating has been used to process the active layer, but due to the dynamic nature of the coating process, this technique is not considered to be industrially scalable. Thus, the work featured herein makes use of blade coating to deposit the active layer and explores techniques to understand the dynamics of the blade coating process. Dynamic measurement techniques and detailed X-ray scattering analysis are used to monitor the solidification process and the developing morphology of pristine materials and their blends.