I11-High Resolution Powder Diffraction
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Brinda
Kuthanazhi
,
Debalina
Banerjee
,
Dmitry
Maslennikov
,
Andrij
Vasylenko
,
Jan P.
Scheifers
,
Cara J.
Hawkins
,
Daniel
Ritchie
,
Craig M.
Robertson
,
Marco
Zanella
,
Troy D.
Manning
,
Luke M.
Daniels
,
Marina R.
Filip
,
Matthew S.
Dyer
,
Laura M.
Herz
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Diamond Proposal Number(s):
[37989]
Open Access
Abstract: We explore multiple-cation chalco–halide phase fields evaluated by their synthetic accessibility using machine learning models. Exploratory synthesis guided by computational tools leads to the discovery of two new compounds; CuSn2SI3 and Cu0.35Sn5.29S2I7, their structures, and electronic and optical properties are reported herein. This is the first report of a stable quaternary compound in the Cu–Sn–S–I phase field. The two new compounds show related crystal structures where Sn4S2I4 layers are a common structural motif in both. These Sn4S2I4 layers are connected by Cu2I2 layers and disordered Cu–Sn–I layers, forming the three-dimensional structures of CuSn2SI3 and Cu0.35Sn5.29S2I7 respectively. Electronic band structure calculations using density functional theory show the presence of a direct band gap in CuSn2SI3 and suggest anisotropic transport, in line with the layered structure of the compound. A mixture of the two compounds with ∼86% CuSn2SI3, shows a band gap in the visible region, close to 2.1 eV and a significant photo-induced charge carrier mobility of ∼1.3 cm2 V−1 s−1. This demonstrates Cu–Sn chalco–halides can form a promising phase space to explore for solar absorber materials, with further design and tuning of band gap.
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Mar 2026
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I07-Surface & interface diffraction
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Rahul A.
Nambiar
,
David P.
Mcmeekin
,
Manuel
Kober Czerny
,
Joel A.
Smith
,
Margherita
Taddei
,
Pietro
Caprioglio
,
Amit
Kumar
,
Benjamin W.
Putland
,
Junke
Wang
,
Karim A.
Elmestekawy
,
Akash
Dasgupta
,
Seongrok
Seo
,
M. Greyson
Christoforo
,
Jin
Yao
,
Daniel J.
Graham
,
Laura M.
Herz
,
David
Ginger
,
Henry J.
Snaith
Diamond Proposal Number(s):
[33462]
Open Access
Abstract: Vacuum deposition of metal halide perovskite is a scalable and adaptable method. In this study, we adopt sequential evaporation to form the perovskite layer and reveal how the relative humidity during the annealing step, impacts its crystallinity and the photoluminescence quantum yield (PLQY). By controlling the humidity, we achieved a significant enhancement of 50 times in PLQY from 0.12% to 6%. This improvement corresponds to an increase in implied open-circuit voltage (Voc) of over 100 meV. We investigate the origin of this enhanced PLQY by combining structural, chemical and spectroscopic methods. Our results show that annealing in a controlled humid environment improves the organic and inorganic halides' interdiffusion throughout the bulk, which in turn significantly reduces non-radiative recombination both in the bulk and at the interfaces with the charge transport layers, which enhanced both the attainable open-circuit voltage and the charge carrier diffusion length. We further demonstrate that the enhanced intermixing results in fully vacuum-deposited FA0.85Cs0.15Pb(IxCl1−x)3 p-i-n perovskite solar cells (PSCs) with a maximum power point tracked efficiency of 21.0% under simulated air mass (AM) 1.5G 100 mW cm−2 irradiance. Additionally, controlled humidity annealed PSCs exhibit superior stability when aged under full spectrum simulated solar illumination at 85 °C and in open-circuit conditions.
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Mar 2025
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E02-JEM ARM 300CF
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Diamond Proposal Number(s):
[35560]
Open Access
Abstract: Nanofibrous active layers offer hierarchical control over molecular structure, and the size and distribution of electron donor:acceptor domains, beyond conventional organic photovoltaic architectures. This structure is created by forming donor pathways via electrospinning nanofibers of semiconducting polymer, then infiltrating with an electron acceptor. Electrospinning induces chain and crystallite alignment, resulting in enhanced light-harvesting and charge transport. Here, the charge transport capabilities are predicted, and charge separation and dynamics are evaluated in these active layers, to assess their photovoltaic potential. Through X-ray and electron diffraction, the fiber nanostructure is elucidated, with uniaxial elongation of the electrospinning jet aligning the polymer backbones within crystallites orthogonal to the fiber axis, and amorphous chains parallel. It is revealed that this structure forms when anisotropic crystallites, pre-assembled in solution, become oriented along the fiber– a configuration with high charge transport potential. Competitive dissociation of excitons formed in the photoactive nanofibers is recorded, with 95%+ photoluminescence quenching upon electron acceptor introduction. Transient absorption studies reveal that silver nanoparticle addition to the fibers improves charge generation and/or lifetimes. 1 ns post-excitation, the plasmonic architecture contains 45% more polarons, per exciton formed, than the bulk heterojunction. Therefore, enhanced exciton populations may be successfully translated into additional charge carriers.
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Nov 2024
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I07-Surface & interface diffraction
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Benjamin M.
Gallant
,
Philippe
Holzhey
,
Joel A.
Smith
,
Saqlain
Choudhary
,
Karim A.
Elmestekawy
,
Pietro
Caprioglio
,
Igal
Levine
,
Alexandra A.
Sheader
,
Esther Y.-H.
Hung
,
Fengning
Yang
,
Daniel T. W.
Toolan
,
Rachel C.
Kilbride
,
Karl-Augustin
Zaininger
,
James M.
Ball
,
M. Greyson
Christoforo
,
Nakita K.
Noel
,
Laura M.
Herz
,
Dominik J.
Kubicki
,
Henry J.
Snaith
Diamond Proposal Number(s):
[33462]
Open Access
Abstract: Perovskite solar cells (PSCs) offer an efficient, inexpensive alternative to current photovoltaic technologies, with the potential for manufacture via high-throughput coating methods. However, challenges for commercial-scale solution-processing of metal-halide perovskites include the use of harmful solvents, the expense of maintaining controlled atmospheric conditions, and the inherent instabilities of PSCs under operation. Here, we address these challenges by introducing a high volatility, low toxicity, biorenewable solvent system to fabricate a range of 2D perovskites, which we use as highly effective precursor phases for subsequent transformation to α-formamidinium lead triiodide (α-FAPbI3), fully processed under ambient conditions. PSCs utilising our α-FAPbI3 reproducibly show remarkable stability under illumination and elevated temperature (ISOS-L-2) and “damp heat” (ISOS-D-3) stressing, surpassing other state-of-the-art perovskite compositions. We determine that this enhancement is a consequence of the 2D precursor phase crystallisation route, which simultaneously avoids retention of residual low-volatility solvents (such as DMF and DMSO) and reduces the rate of degradation of FA+ in the material. Our findings highlight both the critical role of the initial crystallisation process in determining the operational stability of perovskite materials, and that neat FA+-based perovskites can be competitively stable despite the inherent metastability of the α-phase.
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Nov 2024
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Open Access
Abstract: All-optical control of terahertz pulses is essential for the development of optoelectronic devices for next-generation quantum technologies. Despite substantial research in THz generation methods, polarization control remains difficult. Here, we demonstrate that by exploiting band structure topology, both helicity-dependent and helicity-independent THz emission can be generated from nanowires of the topological Dirac semimetal Cd3As2. We show that narrowband THz pulses can be generated at oblique incidence by driving the system with optical (1.55 eV) pulses with circular polarization. Varying the incident angle also provides control of the peak emission frequency, with peak frequencies spanning 0.21–1.40 THz as the angle is tuned from 15 to 45°. We therefore present Cd3As2 nanowires as a promising novel material platform for controllable terahertz emission.
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Apr 2023
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I11-High Resolution Powder Diffraction
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Harry C.
Sansom
,
Leonardo R. V.
Buizza
,
Marco
Zanella
,
James T.
Gibbon
,
Michael
Pitcher
,
Matthew S.
Dyer
,
Troy D.
Manning
,
Vinod R.
Dhanak
,
Laura M.
Herz
,
Henry J.
Snaith
,
John B.
Claridge
,
Matthew J.
Rosseinsky
Open Access
Abstract: A newly reported compound, CuAgBiI5, is synthesized as powder, crystals, and thin films. The structure consists of a 3D octahedral Ag+/Bi3+ network as in spinel, but occupancy of the tetrahedral interstitials by Cu+ differs from those in spinel. The 3D octahedral network of CuAgBiI5 allows us to identify a relationship between octahedral site occupancy (composition) and octahedral motif (structure) across the whole CuI–AgI–BiI3 phase field, giving the ability to chemically control structural dimensionality. To investigate composition–structure–property relationships, we compare the basic optoelectronic properties of CuAgBiI5 with those of Cu2AgBiI6 (which has a 2D octahedral network) and reveal a surprisingly low sensitivity to the dimensionality of the octahedral network. The absorption onset of CuAgBiI5 (2.02 eV) barely changes compared with that of Cu2AgBiI6 (2.06 eV) indicating no obvious signs of an increase in charge confinement. Such behavior contrasts with that for lead halide perovskites which show clear confinement effects upon lowering dimensionality of the octahedral network from 3D to 2D. Changes in photoluminescence spectra and lifetimes between the two compounds mostly derive from the difference in extrinsic defect densities rather than intrinsic effects. While both materials show good stability, bulk CuAgBiI5 powder samples are found to be more sensitive to degradation under solar irradiation compared to Cu2AgBiI6.
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Nov 2021
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E02-JEM ARM 300CF
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Mathias
Uller Rothmann
,
Judy S.
Kim
,
Juliane
Borchert
,
Kilian B.
Lohmann
,
Colum M.
O'Leary
,
Alex A.
Sheader
,
Laura
Clark
,
Henry J.
Snaith
,
Michael B.
Johnston
,
Peter D.
Nellist
,
Laura M.
Herz
Diamond Proposal Number(s):
[21734]
Abstract: Hybrid organic-inorganic perovskites have high potential as materials for solar energy applications, but their microscopic properties are still not well understood. Atomic-resolution scanning transmission electron microscopy has provided invaluable insights for many crystalline solar cell materials, and we used this method to successfully image formamidinium lead triiodide [CH(NH2)2PbI3] thin films with a low dose of electron irradiation. Such images reveal a highly ordered atomic arrangement of sharp grain boundaries and coherent perovskite/PbI2 interfaces, with a striking absence of long-range disorder in the crystal. We found that beam-induced degradation of the perovskite leads to an initial loss of formamidinium [CH(NH2)2+] ions, leaving behind a partially unoccupied perovskite lattice, which explains the unusual regenerative properties of these materials. We further observed aligned point defects and climb-dissociated dislocations. Our findings thus provide an atomic-level understanding of technologically important lead halide perovskites.
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Oct 2020
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E02-JEM ARM 300CF
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Colum
O'Leary
,
Emanuela
Liberti
,
Gerardo
Martinez
,
Christopher
Allen
,
Chen
Huang
,
Mathias
Rothmann
,
Hui
Luo
,
Judy
Kim
,
Laura
Herz
,
Hazel
Assender
,
Lewys
Jones
,
Angus
Kirkland
,
Peter
Nellist
Diamond Proposal Number(s):
[20431, 22317]
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Jul 2020
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[12690]
Open Access
Abstract: Hybrid metal halide perovskites are promising new materials for use in solar cells, however, their chemical stability in the presence of moisture remains a significant drawback. Quasi two-dimensional perovskites that incorporate hydrophobic organic interlayers offer improved resistance to degradation by moisture, currently still at the cost of overall cell efficiency. To elucidate the factors affecting the optoelectronic properties of these materials, we have investigated the charge transport properties and crystallographic orientation of mixed methylammonium (MA)/phenylethylammonium (PEA) lead iodide thin films as a function of MA:PEA and thus the thickness of the ‘encapsulated’ MA lead halide layers. We find that monomolecular charge-carrier recombination rates first decrease with increasing PEA fraction, most likely as a result of trap passivation, but then increase significantly as excitonic effects begin to dominate for thin confined layers. Bimolecular and Auger recombination rate constants are found to be sensitive to changes in electronic confinement, which alters the density of states for electronic transitions. We demonstrate that effective charge-carrier mobilities remain remarkably high (near 10 cm2/Vs) for intermediate PEA content and are enhanced for preferential orientation of the conducting lead-iodide layers along the probing electric field. The tradeoff between trap reduction, electronic confinement and layer orientation leads to calculated charge-carrier diffusion lengths reaching a maximum of 2.5 µm for intermediate PEA content (50%).
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Sep 2016
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I19-Small Molecule Single Crystal Diffraction
I22-Small angle scattering & Diffraction
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Johannes
Sprafke
,
Dmitry
Kondratiuk
,
Michael
Wykes
,
Amber
Thompson
,
Marcus
Hoffman
,
Rokas
Drevinskas
,
Wei-Hsin
Chen
,
Chaw
Keong Yong
,
Joakim
Kärnbratt
,
Joseph
Bullock
,
Marc
Malfois
,
Michael
Wasielewski
,
Bo
Albinsson
,
Laura
Herz
,
Donatas
Zigmantas
,
David
Beljonne
,
Harry
Anderson
Abstract: Linear π-conjugated oligomers have been widely investigated, but the behavior of the corresponding cyclic oligomers is poorly understood, despite the recent synthesis of π-conjugated macrocycles such as [n]cycloparaphenylenes and cyclo[n]thiophenes. Here we present an efficient template-directed synthesis of a π-conjugated butadiyne-linked cyclic porphyrin hexamer directly from the monomer. Small-angle X-ray scattering data show that this nanoring is shape-persistent in solution, even without its template, whereas the linear porphyrin hexamer is relatively flexible. The crystal structure of the nanoring–template complex shows that most of the strain is localized in the acetylenes; the porphyrin units are slightly curved, but the zinc coordination sphere is undistorted. The electrochemistry, absorption, and fluorescence spectra indicate that the HOMO–LUMO gap of the nanoring is less than that of the linear hexamer and less than that of the corresponding polymer. The nanoring exhibits six one-electron reductions and six one-electron oxidations, most of which are well resolved. Ultrafast fluorescence anisotropy measurements show that absorption of light generates an excited state that is delocalized over the whole π-system within a time of less than 0.5 ps. The fluorescence spectrum is amazingly structured and red-shifted. A similar, but less dramatic, red-shift has been reported in the fluorescence spectra of cycloparaphenylenes and was attributed to a high exciton binding energy; however the exciton binding energy of the porphyrin nanoring is similar to those of linear oligomers. Quantum-chemical excited state calculations show that the fluorescence spectrum of the nanoring can be fully explained in terms of vibronic Herzberg–Teller (HT) intensity borrowing.
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Sep 2011
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