LAUSR

The molecular packing structure of conjugated polymers are crucial in determining their optoelectronic properties. The intra and intermolecular interactions (J- and H-type aggregation) in the conjugated polymer films were found to readily facilitate the electron and hole transport, respectively. However, how those different aggregation types influence the photocurrent generation process at the heterojunction is still mysterious, especially for the newly developed semicrystalline conjugated polymers. Here, the prototypical copolymer PM6 is used as a model semicrystalline polymer to tune the relative content of aggregation types with various halogen-free processing solvents. Various measurements reveal that the toluene-processed PM6 film exhibits the increased H-aggregates and crystallinity in the π-π stacking direction compared to its o-Xylene- and trimethylbenzene (TMB)-processed counterparts. This is partly resulted from the weak steric effect and good solubility in the PM6 solution prepared with toluene bearing small molar volume, which strengthens the intermolecular interaction of adjacent polymer segments. After analyzing the photovoltaic properties of the different PM6/Y6 bilayer devices, the faster charge carrier transport, smaller charge recombination, lower energy losses and interfacial energetic disorder can be observed in the toluene-processed device, leading to the synergistically improved short-circuit current density (JSC ) and open-circuit voltage (VOC ). Our findings indicate that the control of the molecular packing structure in terms of aggregation types is a powerful strategy to promote the photocurrent generation process at the conjugated polymer-based heterojunction. This article is protected by copyright. All rights reserved.