Ion slippage through Li+-centered G-quadruplex.

Single-ion conductors have garnered attention in energy storage systems as a promising alternative to currently widespread electrolytes that allow migration of cations and anions. However, ion transport phenomena of most single-ion conductors are affected by strong ion (e.g., Li+)-ion (immobilized anionic domains) interactions and tortuous paths, which pose an obstacle to achieving performance breakthroughs. Here, we present a Li+-centered G-quadruplex (LiGQ) as a class of single-ion conductor based on directional Li+ slippage at the microscopic level. A guanine derivative with liquid crystalline moieties is self-assembled to form a hexagonal ordered columnar structure in the LiGQ, thereby yielding one-dimensional central channels that provide weak ion-dipole interaction and straightforward ionic pathways. The LiGQ exhibits weak Li+ binding energy and low activation energy for ion conduction, verifying its viability as a new electrolyte design.

Guanine-Based G-Quadruplexes Templated by Various Cations toward Potential Use as Single-Ion Conductors.

Inspired by the atomic-sized, shape-regulated features of G-quadruplexes comprising guanine motifs with a monovalent metal cation, the G-quadruplex-forming ability, and properties of a guanine-based π-conjugated Y2 molecule containing bithiophene and peripheral dodecyl chain units in the presence of various cation salts (Li+ , Na+ , K+ , and Mg2+ ) were exploited. A series of structural characterization revealed that Y2 yielded desirable G-quadruplexes with all the tested cations as a consequence of the combination of a hydrogen-bonded cyclic G-quartet, π-stacking, and cation-dipole interactions. The radius and nature of the coordinating cations crucially affected the structural characteristics of G-quadruplexes, leading to variations in the ion migration ability inside the cavity of the G-quadruplex (Li+ >Na+ >K+ >Mg2+ ), as characterized through theoretical and experimental investigations. These results not only improve the understanding of G-quadruplex self-assemblies based on guanine but also provide an impetus for their diverse potential applications, especially in the field of Li batteries.

Effects of the Polarity and Bulkiness of End-Functionalized Side Chains on the Charge Transport of Dicyanovinyl-End-Capped Diketopyrrolopyrrole-Based n-Type Small Molecules.

When designing organic semiconductors, side-chain engineering is as important as modifying the conjugated backbone, which has a significant impact on molecular ordering, morphology, and thus electronic device performance. We have developed three dicyanovinyl-end-capped donor-acceptor diketopyrrolopyrrole-based n-type small molecules (C2C9CN, SiC4CN, and EH4PCN) bearing an identical length of alkyl spacer yet different end-functionalized side chains (i.e., alkyl-, siloxane-, and phosphonate-end pendants). The effects of the end-functionalized side chains on the intrinsic molecular properties, microstructure, and charge transport of the small-molecule series were investigated. In comparison with the alkyl-end side chains, incorporating siloxane-end side chains into the backbone facilitates 2D edge-on oriented high intergrain connectivity/crystallinity and compatibility with the substrate surface, whereas the phosphonate-end analogues have an adverse effect on the film-forming quality due to high polarity. Thereby, an organic field-effect transistor fabricated by SiC4CN shows the best electron mobility up to 1.59 × 10-1 cm2 V-1 s-1 along with a high current on/off ratio >105. This study contributes to our understanding of the role of the end-functionalized side chains (e.g., the effects of polarity and bulkiness of the end groups) for the development of high-performance semiconductors.

Multifaceted Role of a Dibutylhydroxytoluene Processing Additive in Enhancing the Efficiency and Stability of Planar Perovskite Solar Cells.

Significant research efforts are currently being devoted to improving both the crystalline quality and stability of lead halide perovskite absorbers to advance the commercial prospects of perovskite-based solar cells. Herein, we report a simple one-step dibutylhydroxytoluene (BHT) additive-based approach for simultaneously improving the crystallinity and resistance of perovskite films under adverse degradation conditions. We found that BHT, commonly known for its antioxidant properties, can considerably improve the performance of methylammonium lead iodide perovskite solar cells by modulating the chemical environment within the precursor medium to form intermediate complexes, and it can also suppress photooxidation, which results in perovskite degradation under environmental operating conditions. Consequently, a device exhibited a significant power conversion efficiency improvement to 18.1% with the BHT-additive-based perovskite absorber, exceeding the 17.1% efficiency achieved for the control device. The BHT additive also improved the perovskite stability by quenching intermediate reactions resulting in perovskite degradation to an undesirable lead iodide phase, as evidenced by detailed analysis of absorption spectra, grazing-incidence wide-angle X-ray scattering, X-ray photoelectron spectra, and photoluminescence measurements.

Organic Photovoltaics with Multiple Donor-Acceptor Pairs.

Compared with conventional organic solar cells (OSCs) based on single donor-acceptor pairs, terpolymer- and ternary-based OSCs featuring multiple donor-acceptor pairs are promising strategies for enhancing the performance while maintaining an easy and simple synthetic process. Using multiple donor-acceptor pairs in the active layer, the key photovoltaic parameters (i.e., short-circuit current density, open-circuit voltage, and fill factor) governing the OSC characteristics can be simultaneously or individually improved by positive changes in light-harvesting ability, molecular energy levels, and blend morphology. Here, these three major contributions are discussed with the aim of offering in-depth insights in combined terpolymers and ternary systems. Recent exemplary cases of OSCs with multiple donor-acceptor pairs are summarized and more advanced research and perspectives for further developments in this field are highlighted.

An Ultrahigh Mobility in Isomorphic Fluorobenzo[c][1,2,5]thiadiazole-Based Polymers.

To understand the effects rendered on the relevant basic physical properties and device function by controlling the regiochemistry of the cyclopenta[1,2-b:5,4-b']dithiophene-fluorobenzo[c][1,2,5]thiadiazole polymer (hereafter referred to as the CDT-FBT polymer), two polymers, the regiorandom polymer (RA) and regioregular version (RR), respectively, are synthesized and characterized. In addition, an efficient route for synthesizing a key monomer for RR using various synthesis scope and optimizing the reaction conditions is discussed. Although RA exhibits optical, electrochemical, and morphological properties similar to RR, it shows better field-effect transistor (FET) performance. Surprisingly, by employing a capillarity-mediated sandwich-casting process on a nanogrooved substrate, an unprecedented mobility of 17.8 cm2 V-1 s-1 is obtained for RA-based FETs; this mobility value is almost twofold greater than those of the corresponding RR-based FETs. For the first time, this study challenges previously reported results in that high carrier mobility is related to the high degree of polymer order induced by the backbone regioregularity.