Enhanced electrocatalytic properties in dye-sensitized solar cell via Pt/SBA-15 composite with optimized Pt constituent.

The Low utilization and high cost of platinum counter electrode (CE) in the application of dye-sensitized solar cells has limited its large-scale manufacturing in the industry. Herein, a facile pyrolysis combination of Pt and SBA-15 molecular sieve (MS) formed 1.6-1.9 times higher amount and 2-3 times reduced dimension of Pt distributed within porous structure of SBA-15. The composite CE with 20 % of SBA-15 exhibited an enhanced power conversion efficiency of 9.31 %, exceeding that of absolute Pt CE (7.57 %). This superior performance owed to the promoted oxidation-reduction rate of I3-/I- pairs at the CE interface and the increased conductivity of CE materials attributed from well distributed Pt particles. This work has demonstrated the significance of utilizing porous molecular sieves for dispersing catalytic sites when designing a novel type of counter electrode and their application in DSSCs.

High Pressure Rapid Synthesis of LiCrTiO4 with Oxygen Vacancy for High Rate Lithium-Ion Battery Anodes.

Lithium-ion battery based on LiCrTiO4 (LCTO) is considered to be a promising anode material, as they provide higher safety and durability beyond than that of graphite electrode. However, the applications of this transformative technology demand improved inherent electrical conductivity of LCTO as well as a simple and rapid synthetic route. Here, LCTO with oxygen vacancies (OVs) is fabricated using high-pressure synthesis technology in only 40 min. The optimal synthesis pressure is 0.8 GPa (LCTO-0.8). The reversible capacity of LCTO-0.8 at 1C is 131 mA h g-1 after 1000 cycles and the capacity retention is nearly 97%, and the reversible capacity of LCTO synthesized at atmospheric pressure (LCTO-P) is 85 mA h g-1 under the same circumstances. Even at 5C, the reversible capacity is 110 mA h g-1 , which is 77% higher than LCTO-P. Furthermore, it is confirmed by theoretical calculations that the introduction of OVs has the occupation of electronic states at the Fermi level, which greatly enhances the intrinsic conductivity of LCTO. Specifically, the electronic conductivity has increased by two orders of magnitude compared with LCTO-P. Therefore, high-pressure synthesis technology endows LCTO with superior characteristics, providing a new avenue for industrialization.

The influence of three diphenylpyran isomer co-sensitizers with different sterical structures on N719-based dye sensitized solar cells.

Aiming to explore the relationship between the molecular structure and photovoltaic performance, three pyran isomer dyes DO, DM and DP were synthesized and applied as a co-sensitizer with N719 dye in dye-sensitized solar cells (DSCs). These sensitizers were investigated by theoretical calculation, UV-vis absorption spectroscopy and cyclic voltammetry measurement to understand their structure, optical and electrochemical properties. The DSC devices based on N719 and the co-sensitizers were characterized using I-V tests, incident photon-to-current conversion efficiency and electrochemical impedance spectroscopy measurements. As compared to the standard N719-based DSCs, the co-sensitization system of N719 and DM with the most sterical structure exhibited an enhancement of the power conversion efficiency (PCE) by 18% from 7.60% to 8.96%. Both the short-circuit photocurrent density (J sc) and open-circuit voltage (V oc) of the co-sensitized systems were increased resulting from the better maintained N719 dye loading amount on TiO2 as well as the prevention of dye aggregation. Co-sensitization of the DO molecule with less steric hindrance reduced the desorbed N719 dye amount by half leading to a decline of the photo-harvesting ability and photocurrent generation in DSCs.

Dipolar Photosystems: Engineering Oriented Push-Pull Components into Double- and Triple-Channel Surface Architectures.

Push-pull aromatics are not popular as optoelectronic materials because their supramolecular organization is difficult to control. However, recent progress with synthetic methods has suggested that the directional integration of push-pull components into multicomponent photosystems should become possible. In this study, we report the design, synthesis, and evaluation of double- or triple-channel architectures that contain π stacks with push-pull components in parallel or mixed orientation. Moreover, the parallel push-pull stacks were uniformly oriented with regard to co-axial stacks, either with inward or outward oriented push-pull dipoles. Hole-transporting (p) aminoperylenemonoimides (APIs) and aminonaphthalimides (ANIs) are explored for ordered push-pull stacks. For the co-axial electron-transporting (n) stacks, naphthalenediimides (NDIs) are used. In double-channel photosystems, mixed push-pull stacks are overall less active than parallel push-pull stacks. The orientation of the parallel push-pull stacks with regard to the co-axial NDI stacks has little influence on activity. In triple-channel photosystems, outward-directed dipoles in bridging stacks between peripheral p and central n channels show higher activity than inward-directed dipolar stacks. Higher activities in response to direct irradiation of outward-directed parallel stacks reveal the occurrence of quite remarkable optical gating.

Electron-deficient fullerenes in triple-channel photosystems.

Fullerenes of increasing electron deficiency are designed, synthesized and evaluated in multicomponent surface architectures to ultimately build gradients in LUMO levels with nine components over 350 meV down to -4.22 eV.

A collection of fullerenes for synthetic access toward oriented charge-transfer cascades in triple-channel photosystems.

The development of synthetic methods to build complex functional systems is a central and current challenge in organic chemistry. This goal is important because supramolecular architectures of highest sophistication account for function in nature, and synthetic organic chemistry, contrary to high standards with small molecules, fails to deliver functional systems of similar complexity. In this report, we introduce a collection of fullerenes that is compatible with the construction of multicomponent charge-transfer cascades and can be placed in triple-channel architectures next to stacks of oligothiophenes and naphthalenediimides. For the creation of this collection, modern fullerene chemistry-methanofullerenes and 1,4-diarylfullerenes-is combined with classical Nierengarten-Diederich-Bingel approaches.

Toward oriented surface architectures with three coaxial charge-transporting pathways.

We report a synthetic method to build oriented architectures with three coaxial π-stacks directly on solid surfaces. The approach operates with orthogonal dynamic bonds, disulfides and hydrazones, self-organizing surface-initiated polymerization (SOSIP), and templated stack-exchange (TSE). Compatibility with naphthalenediimides, perylenediimides, squaraines, fullerenes, oligothiophenes, and triphenylamine is confirmed. Compared to photosystems composed of two coaxial channels, the installation of a third channel increases photocurrent generation up to 10 times. Limitations concern giant stack exchangers that fail to enter SOSIP architectures (e.g., phthalocyanines surrounded by three fullerenes), and planar triads that can give folded or interdigitated charge-transfer architectures rather than three coaxial channels. The reported triple-channel surface architectures are as sophisticated as it gets today, the directionality of their construction promises general access to multichannel architectures with multicomponent gradients in each individual channel. The reported approach will allow us to systematically unravel the ultrafast photophysics of molecular dyads and triads in surface architectures, and might become useful to develop conceptually innovative optoelectronic devices.

Self-organizing surface-initiated polymerization, templated self-sorting and templated stack exchange: synthetic methods to build complex systems.

In nature, spectacular function is achieved by highly sophisticated supramolecular architectures. Little is known what we would obtain if we could create complexity with similar precision, because the synthetic methods to do so are not available. This account summarizes recent approaches conceived to improve on this situation. With self-organizing surface-initiated polymerization (SOSIP), charge-transporting stacks can be grown directly on solid substrates with molecular-level precision. The extension to templated self-sorting (SOSIP-TSS) offers a supramolecular approach to multicomponent architectures. A solid theoretical framework for the transcription of information by templated self-sorting has been introduced, intrinsic templation efficiencies up to 97% have been achieved, and the existence of self-repair has been shown. The extension to templated stack exchange (SOSIP-TSE) offers the complementary covalent approach. Compatibility of this robust method with the creation of double-channel architectures with antiparallel two-component gradients has been demonstrated.

Solution-processed and air-stable n-type organic thin-film transistors based on thiophene-fused dicyanoquinonediimine (DCNQI) deriatives.

π-Conjugated systems 2a and 2b containing thiophene-fused DCNQI with long alkyl and trifluoromethylphenyl groups were synthesized as potential active materials for solution-processed and air-stable n-type organic thin-film transistors (OTFTs). The electrochemical measurements revealed that the lowest unoccupied molecular orbital (LUMO) of the compounds have an energy level less than -4.0 eV, indicating air stable n-type materials. The long alkyl groups endowed the compounds good solubility and solution-processability. X-ray diffraction measurements revealed the difference of the molecular arrangement depending on the alkyl groups, which were also observed in the UV-vis absorptions of the films. A relatively good mobility up to 0.003 cm(2) V(-1) s(-1) for 2a by spin-coating was obtained with good air stability.