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Significantly Enhanced Molecular Stacking in Ternary Bulk Heterojunctions Enabled by an Appropriate Side Group on Donor Polymer
摘要： Ternary strategy is a promising approach to broaden the photoresponse of polymer solar cells (PSCs) by adopting combinatory photoactive blends. However, it could lead to a more complicated situation in manipulating the bulk morphology. Achieving an ideal morphology that enhances the charge transport and light absorption simultaneously is an essential avenue to promote the device performance. Herein, two polymers with different lengths of side groups (P1 is based on phenyl side group and P2 is based on biphenyl side group) are adopted in the dual-acceptor ternary systems to evaluate the relationship between conjugated side group and crystalline behavior in the ternary system. The P1 ternary system delivers a greatly improved power conversion efficiency (PCE) of 13.06%, which could be attributed to the intense and broad photoresponse and improved charge transport originating from the improved crystallinity. Inversely, the P2 ternary device only exhibits a poor PCE of 8.97%, where the decreased device performance could mainly be ascribed to the disturbed molecular stacking of the components originating from the overlong conjugated side group. The results demonstrate a conjugated side group could greatly determine the device performance by tuning the crystallinity of components in ternary systems.
关键词： ternary systems,ternary bulk heterojunctions,complementary absorption,polymer solar cells,molecular stacking,side chain effect
更新于2025-09-23 15:19:57
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Crystal Multi-Conformational Control Through Deformable Carbon-Sulfur Bond for Singlet-Triplet Emissive Tuning
摘要： Crystal-state luminophores have been of great interest in optoelectronics for years, whereas the excited state regulation at the crystal level is still restricted by the lack of control ways. We report that the singlet–triplet emissive property can be profoundly regulated by crystal conformational distortions. Employing fluoro-substituted tetrakis(arylthio)benzene luminophores as prototype, we found that couples of molecular conformations formed during different crystallizations. The deformable carbon–sulphur bond essentially drove the distortion of the molecular conformation and varied the stacking mode, together with diverse non-covalent interactions, leading to the proportional adjustment of the fluorescence and phosphorescence bands. This intrinsic strategy was further applied for solid-state multicolor emission and mechanoluminescence, probably offering new insights for design of smart crystal luminescent materials.
关键词： Luminescence,Crystal engineering,Noncovalent interactions,Molecular Stacking,Single-crystal conformation
更新于2025-09-19 17:15:36
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Effect of Side-Chain Variation on Single-Crystalline Structures for Revealing the Structurea??Property Relationships of Organic Solar Cells
摘要： The molecular stacking assembly in the active layer plays a significant role in the photovoltaic performance of organic solar cells (OSCs). Here, we report two new small molecular donors with different side chains, FBT-O and FBT-H, and their corresponding fullerene-based OSCs. A slight change in the side chains led to a big difference in the power conversion efficiencies (PCEs). Although the molecular structures of the two donors are similar to each other, PCEs of the devices based on FBT-O were almost three times higher than those of the devices based on FBT-H, with manifold short-circuit current density, fill factor, as well as three orders of magnitude enhancement in the hole mobility. The difference in their single crystal structures was thoroughly investigated, whereby the FBT-O exhibited better planarity leading to appropriate phase separation and domain size. Furthermore, two-dimensional grazing-incidence wide-angle X-ray scattering results of the blend films revealed that the two donors retained a similar stacking structure as compared to the single-crystal structures, thus, establishing a clear relationship between the molecular stacking structure and the device performance.
关键词： side-chain modification,hole mobility,single crystal,molecular stacking structure
更新于2025-09-19 17:13:59
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Alkyl chain-dependent cyano-stilbene derivative's molecular stacking, emission enhancement and fluorescent response to the mechanical force and thermal stimulus
摘要： Two cyano-stilbene derivatives with butyl (C4MPA) and octyl groups (C8MPA) were synthesized to investigate the effects of alkyl chains on molecular stacking, emission enhancement, and mechanofluorochromism. The two compounds displayed weak emissions in monomolecular state and emitted an enhanced fluorescence in crystal state. However, the fluorescence quantum yield of C4MPA (19%) was lower than that of C8MPA (76%). Face-to-face dimer stacking was found only in the C4MPA crystal, in which molecules adopted a nonplanar configuration. The C8MPA crystal presented two kinds of antiparallel 1D arrangement. One involved the antiparallel stacking of nonplanar aromatic moieties. The other consisted of coplanar molecules without π-π stacking, which were responsible for the higher luminescence yield. Moreover, the emission of the C4MPA solid was quenched under mechanical force, whereas the C8MPA solid still emitted a strong fluorescence after grinding. C8MPA lost fluorescence when heated at above 60 °C because of its low melting point, and the supercooling viscous liquid without fluorescence was observed even the sample was cooled to room temperature for 10 h, meaning a very slowly crystallization process. Such non-emissive supercooling viscous liquid might rapidly transform into strongly emissive solid under the mechanical force shearing stimulus. Thus, C8MPA films could be used as sensors for mechanical force and thermal stimuli.
关键词： mechanofluorochromism,emission enhancement,molecular stacking,thermal stimulus,cyano-stilbene derivatives,alkyl chains
更新于2025-09-04 15:30:14