Appropriate Molecular Interaction Enabling Perfect Balance Between Induced Crystallinity and Phase Separation for Efficient Photovoltaic Blends

Two Compatible Acceptors as an Alloy Model with a Halogen-Free Solvent for Efficient Ternary Polymer Solar Cells

A ternary strategy of halogen-free solvent processing can open up a promising pathway for the preparation of polymer solar cells (PSCs) on a large scale and can effectively improve the power conversion efficiency with an appropriate third component. Herein, the green solvent o-xylene (o-XY) is used as the main solvent, and the non-fullerene acceptor Y6-DT-4F as the third component is introduced into the PBB-F:IT-4F binary system to broaden the spectral absorption and optimize the morphology to achieve efficient PSCs. The third component, Y6-DT-4F, is compatible with IT-4F and can form an "alloy acceptor", which can synergistically optimize the photon capture, carrier transport, and collection capabilities of the ternary device. Meanwhile, Y6-DT-4F has strong crystallinity, so when introduced into the binary system as the third component can enhance the crystallization, which is conducive to the charge transport. Consequently, the optimal ternary system based on PBB-F:IT-4F:Y6-DT-4F achieved an efficiency of 15.24%, which is higher than that of the binary device based on PBB-F:IT-4F (13.39%).

Dual-Functionalized MIL-101(Cr) for the Selective Enrichment and Ultrasensitive Analysis of Trace Per- and Poly-fluoroalkyl Substances

The presence of per- and poly-fluoroalkyl substances (PFASs) even at trace levels poses a potential threat to ecological safety and human health. PFASs often require an extraction pretreatment for enrichment before detection and analysis, which is still challenged by the relatively low efficiency because of the limited specific interactions involved. Here, we deliberately introduced multiple interactions into the solid-phase microextraction (SPME) process via a dual-functional modification of MIL-101(Cr), i.e., amination and subsequent fluorination, which is then used as an adsorbent for the efficient enrichment of PFASs. In combination with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), ultrasensitive quantitative analysis is available for nine selected PFASs with high linearities above 0.9941 in the ranges of 0.5-1500 ng/L, low limits of detection of 0.004-0.12 ng/L, satisfactory repeatability and reproducibility with a relative standard deviation (RSD) < 11.6%, as well as excellent performance in complicated real water samples (recovery ratio of 76.2-108.6%). This work represents a rational design of a solid extractant with the desired structure and functionality for the selective enrichment and analysis of PFASs at trace concentrations in real applications.

Significantly Boosting Efficiency of Polymer Solar Cells by Employing a Nontoxic Halogen-Free Additive

Traditional additives like 1,8-diiodooctane and 1-chloronaphthalene were successfully utilized morphology optimization of various polymer solar cells (PSCs) in an active layer, but their toxicity brought by halogen atoms limits their corresponding large-scale manufacturing. Herein, a new nontoxic halogen-free additive named benzyl benzoate (BB) was introduced into the classic PSCs (PTB7-Th:PC₇₁BM), and an optimal power conversion efficiency (PCE) of 9.43% was realized, while there was a poor PCE for additive free devices (4.83%). It was shown that BB additives could inhibit PC₇₁BM's overaggregation, which increased the interface contact area and formed a better penetration path of an active layer. In addition, BB additives could not only boost the distribution of a PTB7-Th donor at the surface, beneficial to suppressing exciton recombination in inverted devices but also boost the crystallinity of a blend layer, which is conducive to exciton dissociation and charge transport. Our work effectively improved a device performance by using a halogen-free additive, which can be referential for industrialization.

Effect of Diethylene Glycol on the Inkjet Printability of Reactive Dye Solution for Cotton Fabrics

Digital inkjet printing technology plays an increasingly important role in textile printing. The printing printability of reactive dye inks is the key to improving the quality of printed fabrics. In this study, an eco-friendly and simple method to improve the inkjet printability of reactive dye solutions was proposed. The influence of diethylene glycol on the surface tension, rheology, and dye molecule aggregation properties for three reactive dye solutions was investigated. The jetting performance of dye solutions was explored by observing droplet formation. Moreover, the color performance of printed cotton fabrics, including reactive dye solution penetration, colorimetric values, and color strength, was evaluated. Addition of diethylene glycol could change the aggregation of dye molecules by hydrophobic forces and hydrogen bonds. Diethylene glycol could inhibit formation of satellite droplets by changing the viscosity and surface tension of solutions, which made the pattern printed on cotton fabrics show regular edge sharpness. Furthermore, the dye solutions containing 10% DEG not only satisfied various properties of reactive dye inks but also had the highest color strength and the deepest and brightest colors.

The Crystallinity Control of Polymer Donor Materials for High-Performance Organic Solar Cells

Bulk heterojunction (BHJ) organic solar cells (OSCs) can be regarded as one of the most promising energy generation technologies for large-scale applications. Despite their several well-known drawbacks, the devices where polymers are employed as the donor are still leading the OSC universe in terms of performance. Such performance generally depends upon various critical factors such as the crystallinity of the material, the crystallization process during the film formation, and also the final film morphology. Despite a few reviews on the structure of the polymer donor materials and device performance, not enough attention has been paid toward the crystallinity problem. Herein, the structure and crystallinity of the representative polymer donor materials and the corresponding device properties have been briefly reviewed. Furthermore, several typical methods for controlling the crystallinity of materials have been summarized and illustrated as well. Moreover, the obstacles lying in the way of successful commercialization of such polymer solar cells have been systematically discussed. The in-depth interpretation of the crystallinity of the polymer donors in this article may stimulate novel ideas in material design and device fabrication.

Aggregation Tuning with Heavily Fluorinated Donor Polymer for Efficient Organic Solar Cells

The fluorination/sulfofication-induced effect in the photovoltaic polymer solar cells (PSCs) needs to be paid much attention. In this work, a new donor polymer PBDB-PS2F was synthesized by heavily fluorinated and decorated S atom on the side chain of benzo[1,2-b:4,5-b']dithiophene (BDT) unit to explore the internal combined effect of F&S on the photoelectric performance. It was found that the heavy fluorination on the side chain could make PBDB-PS2F achieve a low highest occupied molecule orbital (HOMO) energy level of -5.72 eV and weaken the torsion of the main chain and effectively increase the intermolecular π-π* transition. Encouragingly, compared with the counterpart polymer PBDB-PS without the fluorination, PBDB-PS2F exhibited a much intense aggregation at room temperature but showed a tendency of reduced aggregation at high temperatures. This feature gives excellent solution processability and uniform morphology in the active layer of a PBDB-PS2F-based device, enabling an outstanding photovoltaic performance with the power conversion efficiency (PCE) of 13.56% (V_OC = 0.90 V, J_SC = 21.53 mA/cm², FF = 69.68%). Compared with that of the counterpart polymer PBDB-PS with no heavy fluorination, the V_OC of PBDB-PS2F increased by 15.4% and the PCE increased by 30.9%. Thus, the heavy-fluorination-induced effect to construct photovoltaic polymers could be used to improve the performance of polymer solar cells.

Effect of ethylene glycol and its derivatives on the aggregation properties of reactive Orange 13 dye aqueous solution

The aggregation behavior of dyes especially in the dyeing and printing of different textile materials is an important phenomenon which affects the process of dye adsorption and diffusion. In order to avoid the aggregation of dyes, scientists are looking for materials which can inhibit the aggregation process by fabricating the dye solution. Organic solvents have found important influence in the aggregation of dye molecules. Therefore, herein, we report the fabrication of reactive orange 13 dye solutions with the aid of ethylene glycol and its derivative organic solvents to investigate the aggregation behavior of dye molecules by UV-vis absorption spectrum, fluorescence spectrum, surface tension, rheological and particle size measurements. IR spectra were performed to understand the effect of hydrogen bonding on the aggregation behavior of dye molecules. Moreover, transmission electron microscopy was also tested to confirm the effect of organic solvents on the surface morphology of dye molecules. The results show that the reactive Orange 13 dye molecules show aggregation in terms of dimeric and multimeric structures at high dye concentrations due to π–π interaction of naphthalene rings. Moreover, on introducing the ethylene glycol and its derivatives, the dye molecules disaggregate by hydrophobic interactions of dye molecules and organic solvents which destroyed the ice-like structure between the dye molecules and the water molecules. Among the three organic solvents, DME solvent caused more disaggregation of reactive Orange 13 dye molecules due to extra hydrophobic methyl groups in its structure. The results also show that the interaction between Orange 13 dyes and ethylene glycol and its derivatives could decrease the surface tension and particle size of the dye, and increase the quantum yield and viscosity. This research will help to understand the aggregation behavior of dyes and help the textile industries to choose the suitable formulations of dye solutions for coloration of different textile substrates via dyeing and printing methods.

The interaction between Orange 13 dye and ethylene glycol and its derivatives was determined by the dispersion force.

Comparing Benzodithiophene Unit with Alkylthionaphthyl and Alkylthiobiphenyl Side-Chains in Constructing High-Performance Nonfullerene Solar Cells

Using single-bonded and fused aromatic rings are two methods for extending the π-conjugation in the vertical direction of benzo [1,2-b:4,5-b'] dithiophene (BDT) unit. To investigate which method is more efficient in nonfullerene systems, two novel polymers based on alkylthionaphthyl and alkylthiobiphenyl substituted BDT named PBDTNS-FTAZ and PBDTBPS-FTAZ are designed and synthesized. Two polymers only exhibit small differences in structure, but huge differences in photovoltaic properties. They are studied by blended with 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)indanone)-5,5,11,11-tetrakis(4-hexylphenyl)dithieno [2,3-d':2,3'-d']-s-indaceno [1,2-b:5,6-b'] dithiophene (ITIC). The device based on PBDTNS-FTAZ:ITIC showed the best power conversion efficiency (PCE) of 9.63% with the Voc of 0.87 V, a Jsc of 18.06 mA/cm2 and a fill factor of 61.21%, while the PBDTBPS-FTAZ:ITIC only exhibit a maximum PCE of 7.79% with a Voc of 0.86 V, a Jsc of 16.24 mA/cm2 and a relatively low fill factor of 55.92%. Therefore, extending π-conjugation with alkylthionaphthyl is more effective against constructing nonfullerene solar cells.