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Energy loss within organic solar cells (OSCs) is undesirable as it reduces cell efficiency1–4. In particular, non-radiative recombination loss3 and energetic disorder5, which are closely related to the tail states below the band edge and the overall photon energy loss, need to be minimized to improve cell performance. Here, we report how the use of a small-molecule acceptor with torsion-free molecular conformation can achieve a very low degree of energetic disorder and mitigate energy loss in OSCs. The resulting single-junction OSC has an energy loss due to non-radiative recombination of just 0.17 eV and a high power conversion efficiency of up to 16.54% (certified as 15.89% by the National Renewable Energy Laboratory). The findings take studies of organic photovoltaics deeper into a new regime, beyond the limits of energetic disorder and large energy offset for charge generation.An organic solar cell designed with minimal energetic disorder exhibits very low energy loss due to non-radiative recombination and highly efficient operation.

Polymer-fullerene bulk heterojunction solar cells (PSCs) are currently attracting a great deal of attention and gaining increasing importance, having already shown great promise as renewable, lightweight and low-cost energy sources 1 , 2 , 3 , 4 . Recently, the power-conversion efficiency of state-of-the-art PSCs has exceeded 8% in the scientific literature 5 . However, to find viable applications for this emerging photovoltaic technology, further enhancements in the efficiency towards 10% (the threshold for commercial applications) are urgently required 6 . Here, we demonstrate highly efficient PSCs with a certified efficiency of 9.2% using an inverted structure, which simultaneously offers ohmic contact for photogenerated charge-carrier collection and allows optimum photon harvest in the device. Because of the ease of use and drastic boost in efficiency provided by this device structure, this discovery could find use in fully exploiting the potential of various material systems, and also open up new opportunities to improve PSCs with a view to achieving an efficiency of 10%. Polymer solar cells are lightweight and may represent a low-cost source of energy, although efficiency still prohibits many practical applications. Here researchers demonstrate polymer solar cells with a certified efficiency of 9.2%. This is achieved by employing an inverted structure that aids photogenerated charge-carrier collection and photon harvesting.

Toward commercialization of organic solar cells (OSCs), photoactive materials that enable high efficiency yet possess low cost should be developed. Fully non-fused ring electron acceptors (FNEAs) that extend the conjugated skeleton with carbon–carbon (C–C) single bonds solely have lower synthetic costs than their fused-ring counterparts. However, the power conversion efficiencies (PCEs) of FNEAs are lagging due to low acceptor crystallinity and difficulty in the formation of fibrillary bi-continuous interpenetrating network morphology. Herein, we report four FNEAs (NEH-4F, EEH-4F, NBO-4F, and EBO-4F) through rational design of peripheral substituents. Specifically, the encapsulated central core guarantees the planarity of the conjugated skeleton and improves acceptor crystallinity, while the lengthened outer side chains modulate the molecular stacking and regulate the thermodynamic compatibility between the FNEAs and the polymer donor PTTz. Therefore, nanoscale phase separation morphology with bi-continuous interpenetrating fibril network structures was found in the blend of PTTz:EBO-4F, which promotes exciton diffusion and charge transport in solar cells. A record-breaking PCE of 18.04% is thus obtained, which greatly reduces the efficiency gap between FNEAs and fused-ring electron acceptors. These results demonstrate the promising prospect of fabricating high-efficiency OSCs from low-cost FNEAs through rational molecular design. The performance of devices based on fully non-fused ring electron acceptors has been limited due to the low acceptor crystallinity. Here, authors report these acceptors with peripheral substituents that guarantee the planarity of the skeleton, achieving efficiency of 18.04% in organic solar cells.

The novel and appropriate molecular design for polymer donors are playing an important role in realizing high-efficiency and high stable polymer solar cells (PSCs). In this work, four conjugated polymers (PIDT-O, PIDTT-O, PIDT-S and PIDTT-S) with indacenodithiophene (IDT) and indacenodithieno [3,2-b]thiophene (IDTT) as the donor units, and alkoxy-substituted benzoxadiazole and benzothiadiazole derivatives as the acceptor units have been designed and synthesized. Taking advantages of the molecular engineering on polymer backbones, these four polymers showed differently photophysical and photovoltaic properties. They exhibited wide optical bandgaps of 1.88, 1.87, 1.89 and 1.91 eV and quite impressive hole mobilities of 6.01 × 10−4, 7.72 × 10−4, 1.83 × 10−3, and 1.29 × 10−3 cm2 V−1 s−1 for PIDT-O, PIDTT-O, PIDT-S and PIDTT-S, respectively. Through the photovoltaic test via using PIDT-O, PIDTT-O, PIDT-S and PIDTT-S as donor materials and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) as acceptor materials, all the PSCs presented the high open circuit voltages (Vocs) over 0.85 V, whereas the PIDT-S and PIDTT-S based devices showed higher power conversion efficiencies (PCEs) of 5.09% and 4.43%, respectively. Interestingly, the solvent vapor annealing (SVA) treatment on active layers could improve the fill factors (FFs) extensively for these four polymers. For PIDT-S and PIDTT-S, the SVA process improved the FFs exceeding 71%, and ultimately the PCEs were increased to 6.05%, and 6.12%, respectively. Therefore, this kind of wide band-gap polymers are potentially candidates as efficient electron-donating materials for constructing high-performance PSCs.

Building long-lasting antimicrobial and clean surfaces is one of the most effective strategies to inhibit bacterial infection, but obtaining an ideal smart surface with highly efficient, controllable, and regenerative properties still encounters many challenges. Herein, we fabricate an ultrathin brush–hydrogel hybrid coating (PSBMA-P(HEAA- -METAC)) by integrating antifouling polyzwitterionic (PSBMA) brushes and antimicrobial polycationic (P(HEAA- -METAC)) hydrogels. The smart bacterial killing–releasing properties can be achieved independently by the opposite volume and conformation changes between the swelling (shrinking) of P(HEAA- -METAC) hydrogel layer and the shrinking (swelling) of PSBMA brushes. The friction test reveals that both METAC and SBMA components support great lubrication. By tuning the initial organosilane (BrTMOS:KH570) ratios, the prepared PSBMA-P(HEAA- -METAC) coating exhibits different antibacterial abilities from single “capturing–killing” to versatile “capturing–killing–releasing.” Most importantly, 99% of the bacterial-releasing rate can be easily achieved via 0.5 M NaCl treatment. This smart surface not only possesses long-lasting antibacterial performance, only ∼1.09 × 10 cell·cm bacterial residue even after 72 h exposure to bacteria solutions, but also can be regenerated and triggered between water and salt solution multiple times. This work provides a new way to fabricate antibacterial smart hydrogel coatings with bacterial “killing–releasing” functions and shows great potential for biomedical applications.

Cisplatin-based platinum compounds are important clinical chemotherapeutic agents that participate in most tumor chemotherapy regimens. Through density-functional theory calculations, the formation and stability of the inorganic oxide carrier, the mechanisms of the hydrolysis reaction of the activated platinum compound, and its binding mechanism with DNA bases can be studied. The higher the oxidation state of Pt (II to IV), the more electrons transfer from the magnesia–gold composite material to the platinum compound. After adsorption on the composite carrier, 5d←2p coordination bonds of Pt-N are strengthened. For flat and oblique adsorption modes of cisplatin, there is no significant difference in the density of states of the gold and magnesium oxide film, indicating the maintenance of the heterojunction structural framework. However, there are significant changes in the electronic states of cisplatin itself with different adsorption configurations. In the flat configuration, the band gap width of cisplatin is larger than that of the oblique configuration. The Cl-Pt bond range in the Pt(III) compound shows a clear charge reduction on the magnesia film, indicating the Cl-Pt bond is an active site with the potential for decomposition and hydrolysis. The substitution of chloride ions by water can lead to hydrolysis products, enhancing the polarization of the composite and showing strong charge separation. The hydrolysis of the free platinum compound is endothermic by 0.309 eV, exceeding the small activation energy barrier of 0.399 eV, indicating that hydrolysis of this platinum compound is easily achievable. ADME (absorption, distribution, metabolism, and excretion) prediction parameters indicate that hydrolysis products have good ESOL (Estimated SOLubility) solubility and high gastrointestinal absorption, consistent with Lipinski’s rule. During the coordination reaction process, there are significant changes in the distribution of frontier molecular orbitals, with the HOMO (highest occupied molecular orbital) of the initial state primarily located on the purine base, providing the possibility for electron transfer to the empty orbitals of the platinum compound in the LUMO (lowest unoccupied molecular orbital). The HOMO and HOMO-1 of the transition state and product are mainly distributed on the platinum compound, indicating clear electron transfer and orbital rearrangement. The activation energy barrier for the purine coordination reaction with the hydrolysis products is reduced to 0.61 eV, and the dipole moment gradually decreases to 6.77 Debye during the reaction, indicating a reduction in the system’s charge separation and polarization. This contribution is anticipated to provide a new theoretical clue for developing inorganic oxide carriers of platinum compounds.

One of the challenges for high-efficiency single-component-based photoredox catalysts is the low charge transfer and extraction due to the high recombination rate. Here, we demonstrate a strategy to precisely control the charge separation and transport efficiency of the catalytic host by introducing electron or hole extraction interlayers to improve the catalytic efficiency. We use simple and easily available non-conjugated polyelectrolytes (NCPs) (i.e., polyethyleneimine, PEI; poly(allylamine hydrochloride), PAH) to form interlayers, wherein such NCPs consist of the nonconjugated backbone with charge transporting functional groups. Taking CdS as examples, it is shown that although PEI and PAH are insulators and therefore do not have the ability to conduct electricity, they can form good electron or hole transport extraction layers due to the higher charge-transfer kinetics of pendant groups along the backbones, thereby greatly improving the charge transfer capability of CdS. Consequently, the resultant PEI-/PAH-functionalized nanocomposites exhibit significantly enhanced and versatile photoredox catalysis. Conjugated polymers are commonly used as charge conducting systems in photocatalysts, but the use of nonconjugated polymers is less well understood. Here CdS photocatalysts are coated by non-conjugated polyelectrolyte layers, and the influence of the polymer on charge transfer over CdS is explored.

As one of the most important anisotropic intelligent materials, bi-layer stimuli-responsive actuating hydrogels have proven their wide potential in soft robots, artificial muscles, biosensors, and drug delivery. However, they can commonly provide a simple one-actuating process under one external stimulus, which severely limits their further application. Herein, we have developed a new anisotropic hydrogel actuator by local ionic crosslinking on the poly(acrylic acid) (PAA) hydrogel layer of the bi-layer hydrogel for sequential two-stage bending under a single stimulus. Under pH = 13, ionic-crosslinked PAA networks undergo shrinking (-COO−/Fe3+ complexation) and swelling (water absorption) processes. As a combination of Fe3+ crosslinked PAA hydrogel (PAA@Fe3+) with non-swelling poly(3-(1-(4-vinylbenzyl)-1H-imidazol-3-ium-3-yl)propane-1-sulfonate) (PZ) hydrogel, the as-prepared PZ-PAA@Fe3+ bi-layer hydrogel exhibits distinct fast and large-amplitude bidirectional bending behavior. Such sequential two-stage actuation, including bending orientation, angle, and velocity, can be controlled by pH, temperature, hydrogel thickness, and Fe3+ concentration. Furthermore, hand-patterning Fe3+ to crosslink with PAA enables us to achieve various complex 2D and 3D shape transformations. Our work provides a new bi-layer hydrogel system that performs sequential two-stage bending without switching external stimuli, which will inspire the design of programmable and versatile hydrogel-based actuators.

In this study, biocompatible and biodegradable chitosan (CS) nanocapsules are successfully prepared in abundant and easily using carboxyl-functionalized polystyrene (PS) as sacrificial template and cross-linked CS with glutaraldehyde as the shell. First, the monodisperse functionalized PS templates be about 200 nm are made by emulsifier-free emulsion polymerization. Second, nanocapsules are accomplished by fabricating on the basis of chemical cross-linking on the surface of the PS template and removing the core via tetrahydrofuran. The templates and nanocapsules were characterized by FT–IR, 1 H NMR, FESEM, and TEM. All the results confirmed that the nanocapsules are accomplished via this method. By dissolution of ibuprofen in the chloroform droplets when prepare the carboxyl-functionalized PS, drug-loaded nanocapsules are also fabricated. It is found that the loaded drug can be released again in a sustained manner for up to 80 h. The nanocapsules walls have a prominent effect in slowing down the drug release rate.

Lamination technique is one of the most promising and effective approaches to produce flexible organic solar cells (OSCs), with the combination of high throughput and simultaneous encapsulation. In this study, flexible ITO‐free OSCs were successfully fabricated by lamination technique under the optimized temperature and pressure. It is found that the introduction of hole interface layer of PEDOT:MoO3 helps to improve both the film hydrophobicity and the carrier extraction. A high efficiency improvement of about 30% is obtained in the interface‐modified laminating flexible ITO‐free OSCs compared to the conventional laminated device. This work illustrates that anode interface engineering has a significant effect on the improvement of performance of roll‐to‐roll laminated and self‐encapsulated OSCs. Flexible ITO‐free organic solar cells were successfully fabricated and optimized with lamination technology. The PEDOT:MoO3 hole interfacial layer was introduced into the structure, increasing in the short circuit current and the power conversion efficiency of about 30%. PEDOT:MoO3 is found out to promote both the film hydrophobicity and the carrier extraction.