The third generation of photovoltaic technology aims to reduce the fabrication cost and improve the power conversion efficiency (PCE) of solar cells. Singlet fission (SF), an efficient multiple exciton generation (MEG) process in organic semiconductors, is one promising way to surpass the Shockley-Queisser limit of conventional single-junction solar cells. Traditionally, this MEG process has been observed as an intermolecular process in organic materials. The implementation of intermolecular SF in photovoltaic devices has achieved an external quantum efficiency of over 100% and demonstrated significant promise for boosting the PCE of third generation solar cells. More recently, efficient intramolecular SF has been reported. Intramolecular SF materials are modular and have the potential to overcome certain design constraints that intermolecular SF materials possess, which may allow for more facile integration into devices.

We fabricated polyelectrolyte multilayer (PEM) nanofiltration (NF) membranes using a layerby-layer (LbL) method for effective removal of scale-forming divalent cations (Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+) from feedwaters with different salinities. Two polymers with opposite charges, polycation (poly(diallyldimethylammonium chloride), PDADMAC) and polyanion (poly(sodium 4styrenesulfonate), PSS), were sequentially deposited on a commercial polyamide NF membrane to form a PEM. Compared to pristine and PSS-terminated membranes, PDADMAC-terminated membranes demonstrated much higher rejection of divalent cations and selectivity for sodium transport over divalent cations (Na + /X 2+) due to a combination of both Donnan-and size-exclusion effects. A PDADMAC-terminated membrane with 5.5 bilayers exhibited 97% rejection of Mg 2+ with selectivity (Na + /Mg 2+) greater than 30. We attribute the order of cation rejection (Mg 2+ > Ca 2+ > Sr 2+ > Ba 2+) to the ionic size effect, which governs both the hydration radius and hydration energy of the cations. The ionic strength (salinity) of the feed solution had a significant influence on both water flux and cation rejection of PEM membranes. In feed solutions with high ionic strength, abundant NaCl salt screened the charge of the polyelectrolytes and led to swelling of the multilayers, resulting in decreased selectivity (Na + /X 2+) and increased water permeability. The fabricated PEM membranes can be potentially applied to the pretreatment of mild-salinity brackish waters to reduce membrane scaling in the main desalination stage.

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Cycloparaphenylenes (CPPs) have attracted significant attention from theoretical, synthetic, supramolecular and material chemists owing to their aesthetical structures. Since Jasti and co‐workers reported the landmark synthesis of [9]CPP, [12]CPP and [18]CPP, the past ten years have witnessed a remarkable burst in the development of CPP research, from synthetic methodologies to the applications in optoelectronic devices. In this Focus Review, we highlight the representative synthetic strategies to CPPs and attempts on bottom‐up synthesis of carbon nanotubes (CNTs), and mainly focus on the optoelectronic properties studies of functionalized CPPs as well as heteroatoms doped CPP derivatives. Additionally, the potential applications of CPP derivatives in material science are discussed.