A theoretical study of the ligand-controlled palladium-catalysed regiodivergent synthesis of dibenzosilepin derivatives

Palladium-catalysed ligand-controlled 1,n-palladium migration of silicon-tethering substrates provides a regiodivergent synthesis strategy for constructing silicon-bridged π-conjugated compounds possessing a 6,6-fused or a 5,7-fused scaffold. Density functional theory (DFT) calculations were carried out to elucidate the detailed mechanism of this 1,n-palladium migration involving syn- or anti-carbopalladation. The computational results suggest that alkyne insertion is the regioselectivity-determining step. Upon catalysis without the BINAP ligand, the 1,2-insertion of an alkyne into the Pd-aryl bond leads to the formation of 6,6-fused benzophenanthrosiline, which is more favorable than the 2,1-insertion of alkyne by 4.2 kcal mol^-1. The selective formation of 5,7-fused benzofluorenosilepins via the 2,1-alkyne insertion is facilitated by the BINAP ligand. The 1,2-alkyne insertion with the BINAP ligand is disfavoured due to the steric repulsion between the phenyl group of the substrate and the naphthalene group of the BINAP ligand. The 2,1-alkyne insertion with the BINAP ligand orients the ligand away from the phenyl group of the substrate, which can avoid steric repulsion.

Resist or Oxidize: Identifying Molecular Structure-Photostability Relationships for Conjugated Polymers Used in Organic Solar Cells

Although organic solar cells have started to demonstrate competitive power conversion efficiencies of >18 %, their operational lifetimes remain insufficient for wide practical use and the factors influencing the photostability of absorber materials and completed devices are still not completely understood. A systematic study of two series of structurally similar [XTBT]_n and [XTTBTBTT]_n polymers (16 structures in total) reveals the building blocks that enable the highest material stability towards photooxidation: fluorene, silafluorene, carbazole, diketopyrrolopyrrole, and isoindigo. Furthermore, a direct correlation is evident between the electronic properties of the conjugated polymers and their reactivity towards oxygen. The structures with the lowest highest occupied molecular orbital (HOMO) energies show the highest electrochemical oxidation potentials and appear to be the most resistant towards chemical oxidation. These relationships set important guidelines for the further rational design of new absorber materials for efficient and stable organic photovoltaics.

Advances in Synthesis of π-Extended Benzosilole Derivatives and Their Analogs

Benzosiloles and their π-extended derivatives are present in many important advanced materials due to their excellent physical properties. Especially, they have found many potential applications in the development of novel electronic materials such as OLEDs, semiconductors and solar cells. In this review, we have summarized several main approaches to construct (di)benzosilole derivatives and (benzo)siloles fused to aromatic five- and six-membered heterocycles.

Recent Development on Narrow Bandgap Conjugated Polymers for Polymer Solar Cells

There have been exciting developments in the field of polymer solar cells (PSCs) as the potential competitor to the traditional silicon-based solar cells in the past decades. The most successful PSCs are based on the bulk hetero-junction (BHJ) structure, which contains a bicontinuous nanoscale interpenetrating network of a conjugated polymer and a fullerene blend. The power conversion efficiencies (PCEs) of BHJ PSCs have now exceeded 11%. In this review, we present an overview of recent emerging developments of narrow bandgap conjugated polymers for PSCs. We focus on a few important acceptors used in the donor-acceptor type conjugated polymers for highly efficient PSCs. We also reviewed the emerged donor-π-acceptor (D-π-A) side chains polymers. The band-gaps and energy levels as well as the photovoltaic performances of conjugated polymers are discussed.

Water-soluble poly(2,7-dibenzosilole) as an ultra-bright fluorescent label for antibody-based flow cytometry

Water-soluble PEGylated dibenzosilole-based fluorescent polymers were prepared, and the conjugated antibody showed significantly enhanced signal and sensitivity in flow cytometry.

Design, synthesis and optical properties of small molecules based on dithieno[3,2-b:2′,3′-d]stannole and stannafluorene

A series of stable Sn-containing heteroaromatic conjugated oligomers, dialkyl dithieno[3,2-b:2′,3′-d]stannole (DTSn) and stannafluorene (SnF) derivatives, were designed and synthesized.

Nanoimprinted comb structures in a low bandgap polymer: thermal processing and their application in hybrid solar cells

In this paper, we investigate conjugated polymer layers structured by nanoimprint lithography toward their suitability for the fabrication of nanostructured polymer/metal sulfide hybrid solar cells. Consequently, we first study the thermal stability of the nanoimprinted conjugated polymer layers by means of scanning electron microscopy and grazing incidence small-angle X-ray scattering, which reveals a reasonable thermal stability up to 145 °C and sufficient robustness against the solvent mixture used in the subsequent fabrication process. In the second part, we demonstrate the preparation of nanostructured polymer/copper indium sulfide hybrid solar cells via the infiltration and thermal decomposition of a mixture of copper and indium xanthates. Although this step needs temperatures of more than 160 °C, the nanostructures are retained in the final polymer/copper indium sulfide layers. The nanostructured solar cells show significantly improved power conversion efficiencies compared to similarly prepared flat bilayer devices, which is based on a distinct improvement of the short circuit current in the nanostructured solar cells.

Synthesis and properties of D–A copolymers based on dithienopyrrole and benzothiadiazole with various numbers of thienyl units as spacers

By introducing different numbers of thienyl spacers, the properties of D–A type polymers could be modulated, which provides a simple strategy for designing high-performance D–A type photovoltaic polymers based on the existing polymers.

Engineering the band gap and energy level of conjugated polymers using a second acceptor unit

Three conjugated polymers containing two different acceptor units were prepared and used for field effect transistors and polymer solar cells.

Palladium-catalyzed asymmetric synthesis of silicon-stereogenic dibenzosiloles via enantioselective C-H bond functionalization

A Pd-catalyzed asymmetric synthesis of Si-stereogenic dibenzosiloles is developed through enantioselective C-H bond functionalization of prochiral 2-(arylsilyl)aryl triflates. High chemo- and enantioselectivities are achieved by employing a Josiphos-type ligand under mild conditions.