A Three-Dimensional Non-Fullerene Acceptor with Contorted Hexabenzocoronene and Perylenediimide for Organic Solar Cells

Although fullerene derivatives such as [6,6]-phenyl-C61/C71-butyric acid methyl ester (PC61BM/PC71BM) have dominated the the photoactive acceptor materials in bulk heterojunction organic solar cells (OSCs) for decades, they have several drawbacks such as weak absorption, limited structural tunability, prone to aggregation, and high costs of production. Constructing non-fullerene small molecules with three-dimensional (3D) molecular geometry is one of the strategies to replace fullerenes in OSCs. In this study, a 3D molecule, contorted hexa-cata-hexabenzocoronene tetra perylenediimide (HBC-4-PDI), was designed and synthesized. HBC-4-PDI shows a wide and strong light absorption in the whole UV-vis region as well as suitable energy levels as an acceptor for OSCs. More importantly, the 3D construction effectively reduced the self-aggregation of c-HBC, leading to an appropriate scale phase separation of the blend film morphology in OSCs. A preliminary power conversion efficiency of 2.70 % with a champion open-circuit voltage of 1.06 V was obtained in OSCs with HBC-4-PDI as the acceptor, which was the highest among the previously reported OSCs based on c-HBC derivatives. The results indicated that HBC-4-PDI may serve as a good non-fullerene acceptor for OSCs.

Water-Resistance-Based S-Scheme Heterojunction for Deep Mineralization of Toluene

Deep mineralization of low concentration toluene (C7 H8 ) is one of the most significant but challenging reactions in photocatalysis. It is generally assumed that hydroxyl radicals (⋅OH) as the main reactive species contribute to the enhanced photoactivity, however, it remains ambiguous at this stage. Herein, a S-scheme ZnSn(OH)6 -based heterojunction with AlOOH as water resistant surface layer is in situ designed for tuning the free radical species and achieving deep mineralization of C7 H8 . By employing a combination of in situ DRIFTS and materials characterization techniques, we discover that the dominant intermediates such as benzaldehyde and benzoic acid instead of toxic phenols are formed under the action of holes (h+ ) and superoxide radicals (⋅O2 - ). These dominant intermediates turn out to greatly decrease the ring-opening reaction barrier. This study offers new possibilities for rationally tailoring the active species and thus directionally producing dominant intermediates via designing water resistant surface layer.

Three Isomeric Tetraphenylethylene-pyridine Compounds: Synthesis, Crystal Structures, and Photophysical Properties

Many aggregation-induced emission (AIE) molecules based on tetraphenylethylene (TPE) structure have been synthesized, but a clear understanding of the photophysical difference between different isomeric pyridyl-based tetraphenylethylene molecules remains elusive. Herein, we designed a series of isomeric tetraphenylethylene-pyridines (o-Py-TPE, m-Py-TPE, p-Py-TPE) to investigate the influence of the position of N atoms in the pyridine subunit on the photophysical property of the whole molecule by detailed DFT calculations and single-crystal structures analysis. All compounds show typical AIE properties, and notably, the meta pyridyl isomer (m-Py-TPE) shows the highest solid photoluminescence quantum yield (PLQY) up to 64.56 %. Further investigation and DFT calculations indicate that the center C=C bond dihedral angles of the TPE subunit in the solid state of these compounds, which are affected by C-H⋅⋅⋅π interaction, play a vital role in their emission and PLQY properties. This work provides underlying principles for the design of pyridyl-based TPE molecules with high photoluminescent performance in the future.

BODIPY Based OFF-ON Fluorescent Probe for Endogenous Carbon Monoxide Imaging in Living Cells

Carbon monoxide (CO) is one of the signaling molecules that are ubiquitous in humans, which involves in the regulation of human physiology and pathology. In this work, the probe PEC was designed and synthesized based on BODIPY fluorophore that can selectively detect CO through reducing the nitro group to amino group, resulting in a "turn-on" fluorescence response with a simultaneous increase in the concentration of CO. The response is selective over a variety of relevant reactive free radicals, ions, and amino acid species. PEC has the advantages of good stability, good water solubility, and obvious changes in fluorescence signals. In addition, PEC can be used to detect and track endogenous CO in living cells.