Film formation dynamics of spin-coated organic photovoltaics with processing additives

Organic photovoltaics (OPVs) are a promising class of solar technology with potential for lightweight, flexible devices and sustainable manufacturing. The performance and stability of OPV devices are closely linked to the micro-structure of the active layer, which is formed during solution processing and thermal annealing. Recently, the use of processing additives has become widespread in high-performing OPV systems, yet the mechanisms by which these additives influence film formation and change active layer microstructure remains poorly understood.1 This proposal aims to investigate the dynamics of film formation in OPV systems using in-situ GI-WAXS at the NCD-SWEET beamline of the ALBA Synchrotron. Five OPV high performance active layer architectures have been selected, including Y6 homojunctions, binary bulk heterojunctions with PM6 and D18 as donors, and ternary bulk heterojunctions with a novel acceptor.2 These will be combined with five processing additives selected to explore a wide range of physical and chemical properties. By capturing the structural evolution during spin-coating and thermal annealing, this study will provide insight into how additives influence crystallite growth, molecular packing, and phase separation. The results will contribute to a broader understanding of general film formation mechanisms and how those are affected by processing additives, unlocking the potential to build generalisable film formation models. These insights will inform the design of more efficient, replicable, and stable OPV devices, ultimately contributing to the commercial viability of organic solar technologies.