{'fraction_non_alphanumeric': 0.03827460510328068, 'fraction_numerical': 0.013365735115431349, 'mean_word_length': 5.484251968503937, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Building Blocks for High-Efficiency Organic Photovoltaics. Interplay of Molecular, Crystal, and Electronic Properties of Post-Fullerene ITIC Ensembles.

Accurate single-crystal x-ray diffraction data offer a unique opportunity to compare and contrast the atomistic details of bulk heterojunction photovoltaic small-molecule acceptor structure and packing, as well as provide an essential starting point for computational electronic structure and charge transport analysis. Here we report diffraction-derived crystal structures and computational analyses on ITIC and seven derivatives (including three new crystal structures: ITIC-C3, m-ITIC-C6, and ITIC-C4-4F. IDTT acceptors typically pack in a face-to-face fashion with π-π distances ranging from 3.28-3.95 Å. Additionally, edge-to-face packing is observed with S⋯π interactions as short as 3.21-3.24 Å. ITIC end group identities and side chain substituents influence the nature and strength of noncovalent interactions (e.g. H-bonding, π-π) and correlate with the observed packing motif, electronic structure, and charge transport properties of the crystals. Density functional theory (DFT) calculations reveal relatively large nearest-neighbor intermolecular π-π electronic couplings (5.85-56.8 meV) and correlate the nature of the band structure with the dispersion interactions in the single crystals and core-end group polarization effects. This combined experimental and theoretical work reveals key insights into crystal engineering strategies for indacenodithienothiophene (IDTT) acceptors, as well as general design rules for organic solar cell post-fullerene small molecule acceptors.