Spectroscopic Engineering toward Near-Infrared Absorption of Materials Containing Perylene Diimide

The ability to tune the dye structure synthetically has been crucial in the development of materials with tailored properties for given applications. In this contribution, a series of discrete molecules are reported, which are constructed from the perylene diimide (PDI) chromophore and three dyes, namely thienyl diketopyrrolopyrrole (DPPTh2), pyridyl diketopyrrolopyrrole (DPPPyr2), and thienoisoindigo (TII). Through the choice of dye molecule and linking of the dye and PDI through conjugated acetylene bridges, the light-harvesting characteristics can be engineered to exhibit optical absorption in the range 300–900 nm. Each molecule shows ambipolar redox behavior, leading to unique electrochromic behavior

Applying direct heteroarylation synthesis to evaluate organic dyes as the core component in PDI-based molecular materials for fullerene-free organic solar cells

Direct heteroarylation has emerged as a versatile and powerful tool to access π-conjugated materials through atom-economical Pd-catalyzed carbon–carbon bond forming reactions. Employing this synthetic protocol has enabled the facile evaluation of a series of organic dyes in a PDI-dye-PDI framework. Material properties are largely dictated by the PDI components, but the incorporation of either thienoisoindigo, diketopyrrolopyrrole or isoindigo has been shown to influence the ionization potential and absorption profiles of the final materials. Solution-processable organic solar cell devices were fabricated to investigate the influence of the different dye cores on photovoltaic performance when paired with the donor polymer PTB7-Th. It was found that the diketopyrrolopyrrole-based material out-performed the other organic dyes, demonstrating energy losses of less than 0.6 eV, promising efficiencies when cast from non-halogenated solvents and the ability to dictate self-assembly induced by small volume fractions of the high-boiling solvent additive 1,8-diiodooctane to reach best device efficiencies of 4.1%

Direct (Hetero)Arylation Polymerization of a Spirobifluorene and a Dithienyl-Diketopyrrolopyrrole Derivative: New Donor Polymers for Organic Solar Cells

The synthesis and preliminary evaluation as donor material for organic photovoltaics of the poly(diketopyrrolopyrrole-spirobifluorene) (PDPPSBF) is reported herein. Prepared via homogeneous and heterogeneous direct (hetero)arylation polymerization (DHAP), through the use of different catalytic systems, conjugated polymers with comparable molecular weights were obtained. The polymers exhibited strong optical absorption out to 700 nm as thin-films and had appropriate electronic energy levels for use as a donor with PC70BM. Bulk heterojunction solar cells were fabricated giving power conversion efficiencies above 4%. These results reveal the potential of such polymers prepared in only three steps from affordable and commercially available starting material

Effect of side chains on the electronic and photovoltaic properties of diketopyrrolopyrrole-based molecular acceptors

Four molecular electron acceptors based on a common phthalimide end-capped diketopyrrolopyrrole pconjugated backbone, solubilized by different alkyl groups, have been synthesized. The influence of the nature and position of the solubilizing alkyl chains attached at the three constitutive blocks has been investigated. Results collected from UV-Vis absorption spectroscopy, cyclic voltammetry, solar cells fabrication and testing as well as atomic force microscopy show that the mode of substitution has negligible effect at the molecular level but strongly affects the material self-assembling properties, charge carrier transport and in turn, devices performances

Simply Complex: The Efficient Synthesis of an Intricate Molecular Acceptor for High-Performance Air-Processed and Air-Tested Fullerene-Free Organic Solar Cells

A perylene diimide (PDI) flanked diketopyrrolopyrrole (DPP) π-conjugated small molecule has been synthesized through an efficient and sustainable direct heteroarylation protocol. When paired with the donor polymer PTB7-Th, air-processed and tested bulk-heterojunction (BHJ) organic solar cells (OSCs) achieved a high power conversion efficiency (PCE) of 5.6%. The new acceptor showed favorable morphological changes upon solvent vapor annealing leading to a near 3-fold increase in PCE. This result is among the best reported utilizing DPP-based acceptors in air-processed and tested OSCs. All solar cells exhibited good air and light stability over a 35-day evaluation period

The Optimization of Direct Heteroarylation and Sonogashira Cross-Coupling Reactions as Efficient and Sustainable Synthetic Methods To Access π-Conjugated Materials with Near-Infrared Absorption

Two π-conjugated thienoisoindigo-based organic small molecules have been designed to be synthetically accessible through sustainable direct heteroarylation or Sonogashira C–C bond forming cross-coupling reactions utilizing a heterogeneous palladium catalyst. To access these materials, one molecule, TII-ThNaph2, contains a thiophene π-bridge to facilitate direct heteroarylation protocols, whereas the other, TII-AcNaph2, contains an acetylene π-bridge required for Sonogashira couplings. The synthetic route to both final materials was optimized to investigate the reactivity of thienoisoindigo, which to this point has not been significantly explored in comparison to other popular organic dyes such as diketopyrrolopyrrole and isoindigo. Considering the reported interest of thienoisoindigo-based materials in organic solar cells and field-effect transistors, both final materials have been characterized for their optical, electrochemical and thermal properties offering a comparison of the structure–property relationships that manifest as a result of the two different π-bridging units

Thienoisoindigo end-capped molecular donors for organic photovoltaics: Effect of the central π-conjugated connector

The synthesis, characterization and preliminary evaluation of two thienoisoindigo (TII) based molecules as donor materials in air processed bulk heterojunction solar cells are reported herein. The latter were built by grafting TII dyes on two different π-conjugated central cores, namely the cyclopentadithiophene and the fluorene units. Once blended with fullerene derivatives, power conversion efficiencies approaching 3% were measured, ranking amongst the highest reported value for thienoisoindigo-based molecular materials

Thiophene vs thiazole: Effect of the π-connector on the properties of phthalimide end-capped diketopyrrolopyrrole based molecular acceptors for organic photovoltaics

Two phthalimide end-capped diketopyrrolopyrrole based non-fullerene derivatives distinguished by the nature of the π-conjugated connector namely a thiophene or a thiazole ring were synthesized via direct arylation and evaluated as electron acceptor materials in air-processed inverted organic solar cells. It turns out that this simple chemical modification significantly impacts the energetics, the charge transport properties and consequently the photovoltaic performances

The impact of substance use on brain structure in people at high risk of developing schizophrenia

Ventricular enlargement and reduced prefrontal volume are consistent findings in schizophrenia. Both are present in first episode subjects and may be detectable before the onset of clinical disorder. Substance misuse is more common in people with schizophrenia and is associated with similar brain abnormalities. We employ a prospective cohort study with nested case control comparison design to investigate the association between substance misuse, brain abnormality, and subsequent schizophrenia. Substance misuse history, imaging data, and clinical information were collected on 147 subjects at high risk of schizophrenia and 36 controls. Regions exhibiting a significant relationship between level of use of alcohol, cannabis or tobacco, and structure volume were identified. Multivariate regression then elucidated the relationship between level of substance use and structure volumes while accounting for correlations between these variables and correcting for potential confounders. Finally, we established whether substance misuse was associated with later risk of schizophrenia. Increased ventricular volume was associated with alcohol and cannabis use in a dose-dependent manner. Alcohol consumption was associated with reduced frontal lobe volume. Multiple regression analyses found both alcohol and cannabis were significant predictors of these abnormalities when simultaneously entered into the statistical model. Alcohol and cannabis misuse were associated with an increased subsequent risk of schizophrenia. We provide prospective evidence that use of cannabis or alcohol by people at high genetic risk of schizophrenia is associated with brain abnormalities and later risk of psychosis. A family history of schizophrenia may render the brain particularly sensitive to the risk-modifying effects of these substances