The development of ultra-wide-bandgap polymer donors remains crucial for further advancing the performance of organic solar cells (OSCs). In this work, we propose a side-chain topological allocation strategy (SCTAS) and design a series of ultra-wide-bandgap polymer donors (BM1, BM2 and BM3) with a phenanthridine acceptor core in which the allocation patterns of linear versus branched alkyl chains on the π-bridge and the acceptor core are systematically varied. This combinatorial design establishes a complete framework to investigate how side-chain topological distribution influencesoptical/electrochemical properties, aggregation behavior, crystallinity, and donor/acceptor miscibility are comprehensively investigated. Among the three polymers, BM3 with the optimal topological allocation, linear chain on the π-bridge and branched chain on the acceptor core, achieves an optimal balance between close molecular packing and appropriate donor-acceptor miscibility. This is evidenced by temperature-dependent absorption, contact-angle, and GIWAXS measurements, which reveal enhanced crystallinity, favorable face-on orientation, and suitable phase separation in the BM3:Y6 blend. As a result, optimized OSC devices based on BM3:Y6 deliver a maximum power conversion efficiency (PCE) of 15.51 %, with a VOC of 0.836 V, a JSC of 25.26 mA cm−2, and a fill factor of 73.42 %. This work demonstrates that the topological allocation of side chains on both the acceptor core and π-bridge provides an effective approach to simultaneously regulate crystallinity and compatibility of ultra-wide-bandgap donors, offering useful guidelines for the molecular design of high-performance donor materials.
To investigate the fluorescence properties and potential applications of indole derivatives, two indole-based difluoroboron fluorescent dyes (5-BF2 and 6-BF2) were designed and prepared via a straightforward route. The photophysical properties of the two dyes were investigated, revealing solvatochromism and intramolecular charge transfer in seven organic solvents of different polarities, aggregation-induced emission in ethanol/water mixtures, and notable solid-state photoluminescence properties. Furthermore, the relationship between these photophysical behaviors and molecular structure is rationalized by theoretical calculation results. Importantly, the staining agents prepared from the two fluorescent dyes in ethanol/water mixtures enable the visualization of latent fingerprints on smooth surfaces (e.g., blade and aluminum plate). Further analysis reveals that Level 1, 2, and 3 fingerprint details are clearly resolved in the identical regions of the latent fingerprints deposited on both substrates. Moreover, the two staining agents not only yield stable latent fingerprints imaging over time and under varied temperatures, but also allow for the effective visualization of aged latent fingerprints. Mechanistically, the visualization of LFPs under UV light is predominantly attributed to the specific interaction of the two dyes with oleic acid, complemented by hydrophobic-hydrophobic interactions between the sweat-derived hydrophobic components and the dye molecules. This work opens up new avenues for the application of indole-based fluorescent dyes in latent fingerprint visualization.
The selective recognition of enantiomers is of paramount importance in pharmaceutical analysis and biomedical research. In this study, we present a molecular engineering strategy to construct chiral sensing systems by leveraging the aggregation-induced emission (AIE) phenomenon. Three novel amphiphilic luminogens (1-TPE, 2-TPE and 3-PYR) were rationally designed and synthesized. Upon self-assembly in THF/H2O mixtures, these molecules spontaneously formed uniform nanospheres driven by synergistic π-π stacking and hydrophobic interactions, exhibiting pronounced AIE characteristics. Interestingly, circular dichroism (CD) spectroscopy revealed that the achiral molecule 1-TPE could generate supramolecular chirality via spontaneous symmetry breaking, whereas the chiral counterparts (2-TPE and 3-PYR) exhibited significant CD signal amplification through effective chirality transfer. More importantly, both 2-TPE and 3-PYR demonstrated remarkable enantioselective fluorescence responses toward model chiral analytes such as Mandelic acid (MA) and Ethyl lactate. The recognition behavior was found to be highly dependent on host-guest stoichiometry, the spatial configuration of the chiral center, and non-covalent interactions. Notably, 2-TPE enabled the visual discrimination of (S/R)-MA with high contrast at an optimized molar ratio. This work not only provides a deeper understanding of chirality evolution in AIE assemblies but also offers a promising platform for the development of water-compatible, sensitive, and visual chiral sensors.
