Library Reader Issue 04: The eBook Edge

Library resource awareness poster covering electronic books, Kill A Wat energy meters, and Staff Pick Rome.https://dune.une.edu/libraryreader/1003/thumbnail.jp

Gap variability upon packing in organic photovoltaics.

The variation of the HOMO-LUMO band gap is explored for varying packing arrangements of the 4mod BT-4TIC donor-acceptor molecule pair, by means of a high-throughput ab-initio random structure search of packing possibilities. 350 arrangements of the dimer have been relaxed from initial random dispositions, using non-local density-functional theory. We find that the electronic band gap varies within 0.3 eV, and that this magnitude, the binding energy, and the geometry are not significantly correlated. A clearly favoured structure is found with a binding energy of 1.75±0.07 eV, with all but three other arrangements displaying values of less than one third of this highest binding one, which involves the aliphatic chain of 4TIC

4,5-Diazafluorene co-oligomers as electrondeficientlight-emitting materials and selectivefluorescence sensors for mercury(II) cations

4,5-Diazafluorene co-oligomers combine improved electron affinity with strong fluorescence and can be used as electron transporting and light-emitting materials, as well as fluorescent sensors for Hg2+ cations.</p

Quantum Computed Green's Functions using a Cumulant Expansion of the Lanczos Method

In this paper, we present a quantum computational method to calculate the many-body Green's function matrix in a spin orbital basis. We apply our approach to finite-sized fermionic Hubbard models and related impurity models within Dynamical Mean Field Theory, and demonstrate the calculation of Green's functions on Quantinuum's H1-1 trapped-ion quantum computer. Our approach involves a cumulant expansion of the Lanczos method, using Hamiltonian moments as measurable expectation values. This bypasses the need for a large overhead in the number of measurements due to repeated applications of the variational quantum eigensolver (VQE), and instead measures the expectation value of the moments with one set of measurement circuits. From the measured moments, the tridiagonalised Hamiltonian matrix can be computed, which in turn yields the Green's function via continued fractions. While we use a variational algorithm to prepare the ground state in this work, we note that the modularity of our implementation allows for other (non-variational) approaches to be used for the ground state.Comment: 20 pages, 12 figure

3,4-Phenylenedioxythiophenes (PheDOTs) functionalized with electron-withdrawing groupsand their analogs for organic electronics. Remarkably efficient tuning the energy levels in flatconjugated polymers

A novel, facile and efficient one-pot, microwave-assisted method of synthesis allowing an access to a new series of 3,4-phenylenedioxythiophene derivatives with electron-withdrawing groups at the benzene ring (EWG-PheDOT) and their analogs (with an expanded side π-system or with heteroaromatic rings, ArDOT) by the reaction of 2,5-dialkoxycarbonyl-3,4-dihydroxythiophenes with electrophilic aromatic/heteroaromatic compounds in dipolar aprotic solvents has been described. Its applicability over a wide range of novel functionalized ArDOTs as promising building blocks for organic electronic materials has been demonstrated. The structures of selected ArDOTs have been determined by single-crystal X-ray diffraction. The electronic structure of conjugated polymers p[ArDOTs] based on synthesized novel thiophene monomers has been studied theoretically by the DFT PBC/B3LYP/6-31G(d) method. The performed calculations reveal that while the side functional groups are formally not in conjugation with the polymer main chain, they have an unprecedentedly strong effect on the HOMO/LUMO energy levels of conjugated polymers, allowing their efficient tuning by over the range of 1.6 eV. In contrast to that, the energy gaps of the polymers are almost unaffected by such functionalizations and vary within a range of only ≤0.05 eV. Computational predictions have been successfully confirmed in experiments: cyclic voltammetry shows a strong anodic shift of p-doping for the electron-withdrawing CF3 group functionalized polymer p[4CF3-PheDOT] relative to the unsubstituted p[PheDOT] polymer (by 0.55 V; DFT predicted the decrease of the HOMO by 0.58 eV), while very similar Vis-NIR absorption spectra for both polymers in the undoped state indicate that their optical energy gaps nearly coincide (ΔEg &lt; 0.04 eV). © 2018 The Royal Society of Chemistry

Using Deep Machine Learning to Understand the Physical Performance Bottlenecks in Novel Thin‐Film Solar Cells

There is currently a worldwide effort to develop novel materials for solar energy harvesting which are efficient, low cost and do not emit significant levels of CO 2 during manufacture. Currently when a researcher fabricates a novel device from a novel material system, it often takes many weeks of experimental effort and data analysis to understand why any given device/material combination produces an efficient or poorly optimized cell. The net result of this is that it can often take the community tens of years to transform a promising material system (e.g. perovskites/small molecule devices) to a fully optimized cell ready for production. In this work, we develop a new and rapid approach to understanding device/material performance which uses a combination of machine learning, device modeling and experiment. The method is able to provide a set of electrical device parameters (charge carrier mobilities, recombination rates etc..) in a matter of seconds, rather than days and thus offers a fast way to directly link fabrication conditions to device/material performance, pointing a way to further and more rapid optimization of light harvesting devices. We demonstrate the method by using it to understand annealing temperature and surfactant choice and in terms of charge transport and recombination constants for organic solar cells made from the P3HT:PCBM, PBTZT-stat-BDTT-8:PCBM and PTB7:PCBM material systems

Quantum Computed Green's Functions using a Cumulant Expansion of the Lanczos Method

In this paper, we present a quantum computational method to calculate the many-body Green's function matrix in a spin orbital basis. We apply our approach to finite-sized fermionic Hubbard models and related impurity models within Dynamical Mean Field Theory, and demonstrate the calculation of Green's functions on Quantinuum's H1-1 trapped-ion quantum computer. Our approach involves a cumulant expansion of the Lanczos method, using Hamiltonian moments as measurable expectation values. This bypasses the need for a large overhead in the number of measurements due to repeated applications of the variational quantum eigensolver (VQE), and instead measures the expectation value of the moments with one set of measurement circuits. From the measured moments, the tridiagonalised Hamiltonian matrix can be computed, which in turn yields the Green's function via continued fractions. While we use a variational algorithm to prepare the ground state in this work, we note that the modularity of our implementation allows for other (non-variational) approaches to be used for the ground state

How does polymorphism affect the interfacial charge-transfer states in organic photovoltaics?

The bulk heterojunction in organic photovoltaic (OPV) devices is a mixture of polymer (electron donor) and an electron acceptor material (typically functionalized fullerenes), and it is crucial for the device operation, as this is where excitons are split into electrons and holes to produce current. Non-fullerene acceptors (NFAs) are promising new materials for improving the device efficiency, and their solid-state arrangement with respect to the electron donor polymer is critical for the charge mobility and the performance of OPV devices. Although there have been numerous studies on NFAs, most of the current understanding comes from empirical considerations, with little atomistic-level interpretation of why and how the packing influences the charge transport properties of these materials. In this work we describe large-scale (with up to 3462 atoms) DFT simulations for ground and excited states on a number of polymer-NFA interfaces of realistic size, whose NFA domains consist of polymorphs of the same materials. Hence, we bridged the gap between experimental evidence and the intuitive expectation on the importance of intermolecular π-π stacking interactions in the NFA phase. We show that low connectivity leads to highly localized excitons, whereas in phases with a higher connectivity excitons are able to delocalize over multiple directions. Remarkably, excitons with a three-dimensional delocalization were also observed, leading to isotropic mobilities, similarly to fullerenes. Furthermore, a lower charge-transfer exciton binding energy and a lower energy loss between the lowest excitation of the polymer and the first charge-transfer state in the interface were both observed in systems characterized by a highly interconnected NFA phase. This suggests a higher probability of exciton splitting for these interfaces, which could potentially lead to higher device efficiencies

Gap variability upon packing in organic photovoltaics.

The variation of the HOMO-LUMO band gap is explored for varying packing arrangements of the 4mod BT-4TIC donor-acceptor molecule pair, by means of a high-throughput ab-initio random structure search of packing possibilities. 350 arrangements of the dimer have been relaxed from initial random dispositions, using non-local density-functional theory. We find that the electronic band gap varies within 0.3 eV, and that this magnitude, the binding energy, and the geometry are not significantly correlated. A clearly favoured structure is found with a binding energy of 1.75±0.07 eV, with all but three other arrangements displaying values of less than one third of this highest binding one, which involves the aliphatic chain of 4TIC