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Formation of a polycrystalline film of donor material on PEDOT:PSS buffer induced by crystal nucleation



Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most popular anode buffer coated on indium tin oxide. It is thought to improve the inorganic–organic contact, but little is known about its role in organic–organic contact. This study addresses the latter issue by examining how the PEDOT:PSS layer affects the crystallization process of the neighboring layer composed of p-type organic semiconductors in an organic photovoltaic device. Low landing voltage scanning electron microscopic analysis of crystals and aggregates of two donor compounds, tetrabenzoporphyrin (BP) and poly(3-hexylthiophene) (P3HT), showed that PEDOT:PSS effectively nucleates the crystallization or aggregation of the donor material on its surface to form a uniformly thick film of polycrystalline BP or aggregated P3HT molecules. By contrast, a graphitic surface cannot induce structural order of the donor molecules on it. This result implies that pinning of the donor molecules to the acidic PEDOT:PSS surface promotes the heterogeneous nucleation at the organic–organic interface. © 2014 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014, 52, 833–841