Effect of Organic Binders on the Film Morphology of Hydrogen‐Terminated Nanodiamonds Used for Electron Extraction in Organic Solar Cells

Like other carbon nanoparticles, diamond nanoparticles, also known as nanodiamonds (NDs), tend to aggregate when they are dispersed in solution or when they are cast on a substrate. This is mainly due to the versatility of functional groups present on their surface. Previous studies have reported the use of several techniques, including chemical modification, surface active compound usage, and mechanical milling using tiny zirconia beads, for destroying the ND aggregates. Herein, we focus on the deposition of hydrogen‐terminated NDs (H‐NDs) for use as electron transport layer material in inverted organic solar cells and we investigate different approaches to prevent or to eliminate aggregation during the coating of films of H‐NDs, including the reduction of the ND concentration in the dispersions and the blending of H‐NDs powder with additives or binders such as styrene‐butadiene rubber, carboxymethyl cellulose, a combination of both, fluoride‐based polyvinylidene fluoride, and the conjugated polyelectrolyte poly(9,9‐bis(3′‐(N, N‐dimethyl)‐N‐ethylammonium‐propyl‐2,7‐fluorene)‐alt‐2,7‐(9,9‐dioctylfluorene))dibromide (PFN‐Br), in dispersions. The film morphology and more specifically the device's performance and stability were improved in several cases and single nanoparticles of diamonds with small sizes (<20 nm) were observed.