Organic electronic semiconductors have shown remarkable ability to act as photoactive components in organic photovoltaic (OPV) devices over the past decade, with widespread efficiencies of 18-19% for binary systems which are rapidly approaching the fabled 20% efficiency threshold needed for OPV technology commercialisation. In recent years, these advancements have also been employed in organic photocathode devices for water splitting applications and the production of green solar fuels such as hydrogen. However, the dramatic rise in OPV device performance has not been in lock-step with increased stabilities of photovoltaic modules, which often show poor tolerance to oxygen, UV-light, thermal stimuli, and water which lead to photo-oxidative and chemical degradation, alongside thermodynamic instabilities in the photoactive blend. Firstly, in this work, a series of deuterated non-fullerene acceptors (NFAs) were synthesised and characterised for use in thin-film OPV devices with P3HT and PCE11 donor polymers, which were selectively degraded under light and thermal stress to probe the origin of the chemical and morphological device instabilities using ToF-SIMS. Next, conjugated nanoparticle blends of NFAs and donor polymers were used as photoactive materials in water processed OPV devices, as well as hydrogen evolution photocatalysts. The internal morphology of the nanoparticle was modulated from a prototypical core-shell structure to a mixed bulk heterojunction (BHJ) internal structure through the use of a conjugated aromatic surfactant to yield a remarkable ten-fold improvement in H2 evolution of over 60,000 μmol h−1 g−1. The final study involved synthesising a series of alkylated and glycolated statistical n-type naphthalene diimide (NDI) copolymers via a novel post polymerisation functionalisation strategy to incorporate azide and phosphonate pendant functional groups for organic photocathode devices. The side chains of the polymers were modified to enable either
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covalent or non-covalent binding of a molecular catalyst to the polymer surface, in turn enhancing the H2 evolution efficiency.