An Integrated Experimental/Theoretical Study of Structurally Related Poly-Thiophenes Used in Photovoltaic Systems

In this work, a series of eight thiophene-based polymers (exploited as “donors” in bulk heterojunction photovoltaics cells), whose structures were designed to be suitably tuned with the electronic characteristics of the [6,6]-Phenyl C61 butyric acid methyl ester (PCBM), is considered,. The electronic properties of the mono-, di-, trimeric oligomers are reckoned (at the Hartree-Fock and DFT level of the theory) and compared to experimental spectroscopic and electrochemical results. Indeed, electrochemical and spectroscopic results show a systematic difference whose physical nature is assessed and related to the exciton (electron-hole) binding energy (Je,h). The critical comparison of the experimental and theoretical band gaps, i.e., the HOMO-LUMO energy difference, suggests that electrochemical and DFT values are the most suited to being used in the design of a polythiophene-based p-n junction for photovoltaics

An Integrated Theoretical/Experimental Study of Quinolinic-Isoquinolinic Derivatives Acting as Reversible Electrochromes

A series of compounds, featuring an ethenylic bridge and quinoline and isoquinoline end capping units possessing systematically varied substitution patterns, were prepared as molecular materials for electrochromic applications. The different structures were optimized in order to maximize the electrochromic contrast in the visible region, mostly by achieving a completely UV-absorbing oxidized state. Density functional theory (DFT) calculations are exploited in order to rationalize the correlation between the molecular structure, the functional groups' electronic properties, and the electrochemical behavior. It is shown that the molecular planarity (i.e. ring/ring pi conjugation) plays a major role in defining the mechanism of the electrochemical charge transfer reaction, while the substituent's nature has an influence on the LUMO energy. Among the compounds here studied, the (E)-10-methyl-9-(2-(2-methylisoquinolinium1- yl)-vinyl)-1,2,3,4-tetrahydroacri-dinium trifluoromethanesulfonate derivative shows the most interesting properties as an electrochromophore

Maxwell’s demon: the illogical machine or <i>Addendum</i> 2 to the <i>Corrigendum</i> to: Giant Linear and Nonlinear Excitonic Responses in an Atomically Thin Indirect Semiconductor Nitrogen Phosphide

The list of authors reported in the paper J. Phys. Chem. C, 2021, 125, 23, 12738–12757 and their order are not related, in any way, to the actual scientific contribution given to that work. In Addendum 1 we explained the facts and our considerations in detail. Here we report about subsequent developments.</p

Gedankenexperiment: a guide to rational thinking or Addendum 3 to the Corrigendum to: Giant Linear and Nonlinear Excitonic Responses in an Atomically Thin Indirect Semiconductor Nitrogen Phosphide

The list of authors and their order in the paper J. Phys. Chem. C, 2021, 125, 23, 12738–12757 do not reflect, in any way, the actual scientific contribution given to that work. In Addendum 1, we provided a detailed explanation of the facts and our considerations. Here, we further deepen our considerations by commenting the results of a systematic bibliographical study.</p

Conflicting effect of chemical doping on the thermoelectric response of ordered PEDOT aggregates

Poly(3,4-ethylenedioxythiophene) (PEDOT) semiconductor plays a relevant role in the development of organic thermoelectric (TE) devices for low-power generation. While dopant counterions are usually needed to provide electrical conductivity, their overall effects on the thermoelectric response of the systems are unknown and uncontrolled. Here, we present a first principles study of the electronic and thermal transport of PEDOT crystalline assemblies, specifically analysing the role played by tosylate dopants on the thermoelectric figure of merit of the doped system. Our results demonstrate that, beside the desired charging effect, the presence of dopants impacts the bulk configuration by inflating the packing structure and worsening the intrinsic transport properties of the PEDOT host. This provides a rationale for the necessity of controlling the optimal amount and the structural incorporation of dopant in order to maximize the thermoelectric response of organic materials

Thermoelectric figure of merit of polymeric systems for low-power generators

The request of thermoelectric materials for low-power and flexible applications fosters the investigation of the intrinsic electron and thermal transport of conducting polymeric chains, which are building blocks of the complex variety of organic composites proposed in experimental samples. Using calculations from first principles and the Landauer approach for both electron and phonon carriers, we study the thermoelectric figure of merit zT of three representative and largely used polymer chains, namely poly(3,4-ethylenedioxythiophene), polyaniline and polyfluorene. Our results provide an upper-limit estimate of zT, due to the intrinsic electronic and vibrational properties of the selected compounds, and pave the way to a microscopic understanding of the mechanisms that affect their electronic and transport characteristics in terms of structural distortions and chemical doping

A novel synthetic strategy for magnetite-type compounds. A combined experimental and DFT-computational study

The dynamics of the early stage reaction between benzyl alcohol and Fe(acetylacetonate)3 is studied by exploiting the Dynamic Reaction Coordinate (DRC) approach, at the PBE0/6-31G* level of theory. Analysis of the DRC trajectory provides a detailed molecular insight into the catalytic effect observed in the acidic reaction environment, compared to the neutral one. The presence of an additional proton in the reaction system, meant to simulate an acidic reaction environment, dramatically affects the reaction path: both by decreasing the activation energy of the complex dissociation and leading to the formation of acetone