Browsing by Author "Mitchell, VD"

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    Increased efficiency of organic solar cells by seeded control of the molecular morphology in the active layer
    (Wiley-VCH GmbH, 2022-03-29) Rahaman, MH; Holland, J; Hossain, MA; Duan, LP; Hoex, B; Mota-Santiago, P; Mitchell, VD; Uddin, A; Stride, JA
    The performance of non-fullerene, polymer bulk heterojunction (BHJ) organic photovoltaic devices has a significant correlation with the molecular morphology of the donor and acceptor. The authors show that small organic molecules coordinated to a metal oxide, an electron transport seed layer (ETSL), can profoundly modify the donor:acceptor molecular morphology of inverted organic photovoltaic (OPV) devices. Using grazing incidence wide angle X-ray scattering (GIWAXS), the authors show that a PTB7-Th:IEICO-4F BHJ active layer has a higher degree of face-on molecular alignment on ETSL-1 (biphenyl-4,4′-dicarboxylic acid, coordinated to ZnO), whilst for naphthalene-2,6-dicarboxylic acid coordinated to ZnO (ETSL-2), it is reduced. Devices of PTB7-Th:IEICO-4F BHJ prepared on ETSL-1 had a 19.91% increase in the average power conversion efficiency (PCE), a 1.56% increase in the fill factor (FF), and a 16.66 ± 0.2% enhancement in the short circuit current density. The observed improvements are believed to be due to significant modifications to the oxide-BHJ interfacial region of ETSL-1, namely the elimination of nano-ridges and defect centers, along with an enhanced wettability. These factors can be correlated with the enhanced device performances, leading to the conclusion that the modulation of the molecular morphology of donor:acceptor blends by ETSL-1 has a broad impact on improving OPV cell efficiencies. © 2022 The Authors. Solar RRL published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution Licence
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    Total scattering measurements at the Australian Synchrotron Powder Diffraction beamline: capabilities and limitations
    (International Union of Crystallography, 2023-03-01) D'Angelo, AM; Brand, HEA; Mitchell, VD; Hamilton, JL; Oldfield, DT; Liu, ACY; Gu, QF
    This study describes the capabilities and limitations of carrying out total scattering experiments on the Powder Diffraction (PD) beamline at the Australian Synchrotron, ANSTO. A maximum instrument momentum transfer of 19 Å−1 can be achieved if the data are collected at 21 keV. The results detail how the pair distribution function (PDF) is affected by Qmax, absorption and counting time duration at the PD beamline, and refined structural parameters exemplify how the PDF is affected by these parameters. There are considerations when performing total scattering experiments at the PD beamline, including (1) samples need to be stable during data collection, (2) highly absorbing samples with a μR > 1 always require dilution and (3) only correlation length differences >0.35 Å may be resolved. A case study comparing the PDF atom–atom correlation lengths with EXAFS-derived radial distances of Ni and Pt nanocrystals is also presented, which shows good agreement between the two techniques. The results here can be used as a guide for researchers considering total scattering experiments at the PD beamline or similarly setup beamlines. © 2023 The Authors - Open Access CC-BY Licence 4.0
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    Total scattering measurements at the Australian Synchrotron Powder Diffraction beamline: capabilities and limitations
    (Australian Nuclear Science and Technology Organisation, 2021-11-24) D'Angelo, AM; Gu, QF; Brand, HEA; Mitchell, VD; Hamilton, JL; Liu, ACY; Oldfield, DT
    The PD beamline at the Australian Synchrotron (ANSTO) consistently receives requests to carry out total scattering experiments for various materials including battery electrodes, piezoelectrics and coordination frameworks. In this study we describe the capabilities and limitations of carrying out total scattering experiments on the Powder Diffraction beamline. A maximum instrument momentum transfer of 19 Å-1 can be achieved. Our results detail how the pair distribution function is affected by Qmax, absorption, and counting time duration at the PD beamline. We also trial a variable counting time strategy using the Mythen II detector. Refined structural parameters exemplify how the PDF is affected by these parameters. Total scattering experiments can be carried out at PD although there are limitations. These are: (1) only measurements on stable systems and at non-ambient conditions is possible if the temperature is held during data collection, (2) it is essential to dilute highly absorbing samples (μR>1), and (3) only correlation lengths >0.35 Å may be resolved. A case study comparing the PDF atom-atom correlation lengths with EXAFS derived radial distances of Ni and Pt nanoparticles is also presented, which shows good agreement between the two techniques. The results here can be used as a guide for researchers considering total scattering experiments at the PD beamline. © The Authors