Solar Cell Enhancement from Supercritical CO2 Dye Surface Modification of Mesoporous TiO2 Photoanodes.

In recent years, in an effort to reach Net Zero Emissions, there has been growing interest by various academic and industry communities to develop chemicals and industrial processes that are circular, sustainable and green. We report the rapid, simple and effective surface modification of a porous metal oxide with organic dyes using supercritical carbon dioxide (scCO2). Titanium dioxide (TiO2) photoanodes were coated in very short times, under mild conditions and the excess dye recovered afterwards for reuse. The process obviates the need for conventional toxic solvents, the generation of unwanted waste streams, and more importantly, we see an unexpected device performance enhancement of 212 and 163 % for TerCOOTMS, 2 a and TerCN/COOTBDMS, 4 dyes, respectively, when compared to the conventional solvent deposition method.

Presence of Short Intermolecular Contacts Screens for Kinetic Stability in Packing Polymorphs.

Polymorphism is pervasive in molecular solids. While computational predictions of the molecular polymorphic landscape have improved significantly, identifying which polymorphs are preferentially accessed and experimentally stable remains a challenge. We report a framework that correlates short intermolecular contacts with polymorphic stability. The presence of short contacts between neighboring molecules prevents structural rearrangement and stabilizes the packing arrangement, even when the stabilized polymorph is not enthalpically favored. In the absence of such intermolecular short contacts, the molecules have added degrees of freedom for structural rearrangement, and solid-solid polymorphic transformations occur readily. Starting with a series of core-halogenated naphthalene tetracarboxylic diimides, we establish this framework with the packing polymorphs of more than 20 compounds, ranging from molecular semiconductors to pharmaceutics and biological building blocks. This framework, widely applicable across molecular solids, can help refine computational predictions by identifying the polymorphs that are kinetically stable.

Structural elucidation of a hy-droxy-cineole product obtained from cytochrome P450 monooxygenase CYP101J2 catalysed transformation of 1,8-cineole.

1,8-Cineole is an abundant natural product that has the potential to be transformed into other building blocks that could be suitable alternatives to petroleum-based chemicals. Mono-hydroxy-lation of 1,8-cineole can potentially occur at eight different carbon sites around the bicyclic ring system. Using cytochrome P450 monooxygenase CYP101J2 from Sphingobium yanoikuyae B2, the hy-droxy-lation can be regioselectively directed at the C atom adjacent to the methyl-substituted quaternary bridgehead atom of 1,8-cineole. The unambiguous location of the hydroxyl functionality and the stereochemistry at this position was determined by X-ray crystal analysis. The mono-hydroxy-lated compound derived from this microorganism was determined to be (1S)-2a-hy-droxy-1,8-cineole (trivial name) or (1S,4R,6S)-1,3,3-trimethyl-2-oxabi-cyclo-[2.2.2]octan-6-ol (V) (systematic), C10H18O2. In the solid state this compound exhibits an inter-esting O-H⋯O hydrogen-bonding motif.

Ambient Protection of Few-Layer Black Phosphorus via Sequestration of Reactive Oxygen Species.

Few-layer black phosphorous (BP) has emerged as a promising candidate for next-generation nanophotonic and nanoelectronic devices. However, rapid ambient degradation of mechanically exfoliated BP poses challenges in its practical deployment in scalable devices. To date, the strategies employed to protect BP have relied upon preventing its exposure to atmospheric conditions. Here, an approach that allows this sensitive material to remain stable without requiring its isolation from the ambient environment is reported. The method draws inspiration from the unique ability of biological systems to avoid photo-oxidative damage caused by reactive oxygen species. Since BP undergoes similar photo-oxidative degradation, imidazolium-based ionic liquids are employed as quenchers of these damaging species on the BP surface. This chemical sequestration strategy allows BP to remain stable for over 13 weeks, while retaining its key electronic characteristics. This study opens opportunities to practically implement BP and other environmentally sensitive 2D materials for electronic applications.

Chemically Altering the Solubility and Durability of Dyes for Sensitized Solar Cells.

By designing dyes with fluoroalkyl groups, the optical and electronic properties of the alkyl analogue were maintained while dramatically altering the solubility. Dyes, F-TABTA (8) and its masked derivative F-TABTSi (9), that enable them to be deposited under conventional organic solvent and scCO2 conditions, respectively, were developed. In liquid DSSC devices, the fluoroalkyl dye (F-TABTA, 8) performs slightly better than its alkyl analogue (D21L6, 10), and interestingly, it was found that the former device showed better stability over time. Deploying the silyl-masked precursor F-TABTSi (9), this dye was deposited onto TiO2 photoanodes from scCO2 in very short contact times (2.5 h), and ECEs of 7.70% were obtained that exceed the performance of the alkyl dye when deposited by conventional methods.

An N-ethylated barbituric acid end-capped bithiophene as an electron-acceptor material in fullerene-free organic photovoltaics.

A new evaporable electron acceptor material for organic photovoltaics based on N-ethyl barbituric acid bithiophene (EBB) has been demonstrated. Bilayer devices fabricated with this non-fullerene acceptor and boron subphthalocyanine chloride (SubPc) donor produce power conversion efficiencies as high as 2.6% with an extremely large open-circuit voltage approaching 1.4 V.

Indan-1,3-dione electron-acceptor small molecules for solution-processable solar cells: a structure-property correlation.

A structure-device performance correlation in bulk heterojunction solar cells for new indandione-derived small molecule electron acceptors, FEHIDT and F8IDT, is presented. Devices based on the former exhibit higher power conversion efficiency (2.4%) and higher open circuit voltage, a finding consistent with reduced intermolecular interactions.

Nucleobase mediated, photocatalytic vesicle formation from an ester precursor.

We report the use of photoinduced electron transfer to drive reductive cleavage of an ester to produce bilayer-forming molecules; specifically, visible photolysis in a mixture of a decanoic acid ester precursor, hydrogen donor molecules, and a ruthenium-based photocatalyst that employs a linked nucleobase (8-oxo-guanine) as an electron donor generates decanoic acid. The overall transformation of the ester precursor to yield vesicles represents the use of an external energy source to convert nonstructure forming molecules into amphiphiles that spontaneously assemble into vesicles. The core of our chemical reaction system uses an 8-oxo-G-Ru photocatalyst, a derivative of [tris(2,2'-bipyridine)-Ru(II)](2+).

The design and synthesis of porphyrin/oligiothiophene hybrid monomers.

In an effort to build effective photovoltaic cells based on porphyrin-functionalised polythiophenes we have focused on synthetic routes to three monomer types. By controlling the geometric structure of the monomer, oxidation of these materials should produce polymers with different architectural structures, and as a result, different opto-electronic properties. Employing Wittig protocols allowed access to monomers in which the porphyrin moiety is connected to the beta-position of the thiophene via an alkene linkage. In addition, monomers were constructed using porphyrin condensation methods to afford alpha-thiophene meso-substituted porphryins. Another set of monomers was also prepared via porphyrin condensation routes, but instead utilising beta-formylthiophenes. By utilising different formyloligothiophenes we were able to generate a series of monomers that can be used to control the loading of the porphyrin in the polythiophene matrix.

Toward functionalized conducting polymers: synthesis and characterization of novel beta-(styryl)terthiophenes.

Metal-catalyzed coupling methodologies have been employed in the synthesis of the key building block 3'-formyl-2,2':5',2"-terthiophene. Wittig olefinations with this aldehyde have produced five novel beta-styryl-substituted terthiophene monomers. These materials have been fully characterized by NMR spectroscopy, microanalysis, mass spectrometry, and X-ray crystal structure analysis. The results from the UV/visible spectroscopy and cyclic voltammetric investigations are reported.

7-Bromoquinolin-8-ol.

Structure analysis of the title compound, C(9)H(6)BrNO, has established that bromination of an 8-hydroxyquinoline derivative occurred in the 7-position. Intermolecular and weak intramolecular O-H.N hydrogen bonds are present, the former causing the molecules to pack as hydrogen-bonded dimers in the solid state.