E02-JEM ARM 300CF
|
Xinjuan
Li
,
Zhao
Jiang
,
Si
Chen
,
Yi
Tang
,
Bofeng
Xue
,
Tianhao
Wu
,
Yang
Lu
,
Xavier
Moya
,
Akshay
Rao
,
Zhongzheng
Yu
,
Caterina
Ducati
Diamond Proposal Number(s):
[39081]
Open Access
Abstract: Perovskite quantum dots (PeQDs) offer high photoluminescence quantum efficiencies, precise spectral tunability, and solution-processability, making them promising for advanced optoelectronics. However, their structural and defect evolution under thermal stress remains poorly understood. Here, direct nanoscale insights are provided into temperature-driven phase transition and defect dynamics in CsPbBr3 PeQDs using high-resolution, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images, 4D STEM, and photoluminescence spectroscopy. Sub-ångström imaging at room temperature reveals inherent atomic features and octahedral tilting of the lead halide perovskite lattice in PeQDs, suggesting a pre-tilted, low-symmetry state before thermal perturbation. The cryogenic cooling induces a reversible orthorhombic-to-monoclinic phase transition, distinct from bulk perovskite behavior and accompanied by severe strain localization exceeding 20% at surfaces and grain boundaries. A controlled cryogenic post-synthesis treatment can effectively heal defects and improve radiative recombination, whereas prolonged cryo-treatment introduces irreversible structural degradation. These findings highlight the intrinsic structural flexibility of PeQDs and provide a scalable post-synthesis treatment method to optimize the stability and efficiency of QDs for various optoelectronic applications.
|
Dec 2025
|
|
E02-JEM ARM 300CF
|
Dengyang
Guo
,
Thomas A.
Selby
,
Simon
Kahmann
,
Sebastian
Gorgon
,
Linjie
Dai
,
Milos
Dubajic
,
Terry
Chien-Jen Yang
,
Simon M.
Fairclough
,
Thomas
Marsh
,
Ian E.
Jacobs
,
Baohu
Wu
,
Renjun
Guo
,
Satyawan
Nagane
,
Tiarnan A. S.
Doherty
,
Kangyu
Ji
,
Cheng
Liu
,
Yang
Lu
,
Taeheon
Kang
,
Capucine
Mamak
,
Jian
Mao
,
Peter
Muller-Buschbaum
,
Henning
Sirringhaus
,
Paul A.
Midgley
,
Samuel D.
Stranks
Diamond Proposal Number(s):
[35894]
Open Access
Abstract: The high optoelectronic quality of halide perovskites makes them suitable for use in optoelectronic devices and, recently, in emerging quantum emission applications. Advancements in perovskite nanomaterials have led to the discovery of processes in which luminescence decay times are below 100 picoseconds, stimulating the exploration of even faster radiative rates for advanced quantum applications, which have only been realized in III–V materials grown using costly epitaxial growth methods. Here we discovered ultrafast quantum transients with timescales of around two picoseconds at low temperature in bulk formamidinium lead iodide films grown via scalable solution or vapour approaches. Using a multimodal strategy, combining ultrafast spectroscopy, optical and electron microscopy, we show that these transients originate from quantum tunnelling in nanodomain superlattices. The outcome of the transient decays, that is, photoluminescence, mirrors the photoabsorption of the states, with an ultranarrow linewidth at low temperature that can reach <2 nm (~4 meV). Localized correlation of the emission and structure reveals that the nanodomain superlattices are formed by alternating ordered layers of corner-sharing and face-sharing octahedra. This discovery opens new applications leveraging intrinsic quantum properties and demonstrates powerful multimodal approaches for quantum investigations.
|
Oct 2025
|
|
E02-JEM ARM 300CF
I07-Surface & interface diffraction
|
Diamond Proposal Number(s):
[32017, 35227]
Open Access
Abstract: Thermoelectric materials, enabling direct waste-heat to electricity conversion, need to be highly electrically conducting while simultaneously thermally insulating. This is fundamentally challenging since electrical and thermal conduction usually change in tandem. In quasi-two-dimensional conjugated coordination polymer films we discover an advantageous thermoelectric transport regime, in which charge transport is defect-tolerant but heat propagation is defect-sensitive; it imparts the ideal mix of antithetical properties—temperature-activated, exceptionally low lattice thermal conductivities of 0.2 W m−1 K−1 below Kittel’s limit originating from small-amplitude, quasi-harmonic lattice dynamics with disorder-limited lifetimes and vibrational scattering length on the order of interatomic spacing, and high electrical conductivities up to 2000 S cm−1 with metallic temperature dependence, notably in poorly crystalline structures with paracrystallinity >10%. These materials offer attractive properties, such as ease of processing and defect tolerance, for applications, that require fast charge, but slow heat transport.
|
Jul 2025
|
|
E02-JEM ARM 300CF
|
Diamond Proposal Number(s):
[28500, 30057, 30160, 30157, 31872]
Open Access
Abstract: Organic molecular crystals encompass a vast range of materials from pharmaceuticals to organic optoelectronics, proteins and waxes in biological and industrial settings. Crystal defects from grain boundaries to dislocations are known to play key roles in mechanisms of growth1,2 and in the functional properties of molecular crystals3,4,5. In contrast to the precise analysis of individual defects in metals, ceramics and inorganic semiconductors enabled by electron microscopy, substantially greater ambiguity remains in the experimental determination of individual dislocation character and slip systems in molecular materials3. In large part, nanoscale dislocation analysis in molecular crystals has been hindered by the low electron doses required to avoid irreversibly degrading these crystals6. Here we present a low-dose, single-exposure approach enabling nanometre-resolved analysis of individual dislocations in molecular crystals. We demonstrate the approach for a range of crystal types to reveal dislocation character and operative slip systems unambiguously.
|
Mar 2025
|
|
E02-JEM ARM 300CF
|
Sangcheol
Yoon
,
Braulio
Reyes-Suárez
,
Sang T.
Pham
,
Hervé
Vezin
,
Yeny A.
Tobon
,
Myeongjae
Lee
,
Sam
Mugiraneza
,
Brian Minki
Kim
,
Mariane Yuka Tsubaki
Oide
,
Seongju
Yoo
,
Seunggu
Lee
,
Shu Hui
Wang
,
Sean M.
Collins
,
Christopher M.
Bates
,
Yongsup
Park
,
Bongsoo
Kim
,
G. N. Manjunatha
Reddy
,
Thuc-Quyen
Nguyen
Diamond Proposal Number(s):
[34607]
Abstract: Understanding efficiency–durability relationships and related mitigation strategies is an important step toward the commercialization of organic photovoltaics (OPVs). Here, we report that a photoactivated 6-bridged azide cross-linker (6Bx) improves the morphological stability by suppressing the thermally activated diffusion of (Y6) acceptor molecules in PM6:Y6 bulk-heterojunction (BHJ)-based OPVs. Cross-linked PM6:Y6 (0.05 wt % 6Bx) BHJ OPVs retain 93.4% of the initial power conversion efficiency upon thermal aging at 85 °C for 1680 h (T80 = 3290 h). Molecular origins of enhanced thermal stability are corroborated by optical spectroscopy, surface imaging, 2D solid-state nuclear magnetic resonance (ssNMR), Raman spectroscopy, scanning electron diffraction (SED) measurements, and analysis of the BHJ thin films. The facile single-step cross-linking strategy in conjugation with advanced characterization methods presented in the study paves the way toward developing durable OPVs based on non-fullerene acceptors (NFAs).
|
Dec 2024
|
|
E02-JEM ARM 300CF
|
Diamond Proposal Number(s):
[28500, 26822, 28789, 30157]
Open Access
Abstract: Waxes comprise a diverse set of materials from lubricants and coatings to biological materials such as the intracuticular wax layers on plant leaves that restrict water loss to inhibit dehydration. Despite the often mixed hydrocarbon chain lengths and functional groups within waxes, they show a propensity for ordering into crystalline phases, albeit with a wealth of solid solution behavior and disorder modes that determine chemical transport and mechanical properties. Here, we reveal the microscopic structure and heterogeneity of replica leaf wax models based on the dominant wax types in the Schefflera elegantissima plant, namely C31H64 and C30H61OH and their binary mixtures. We observe defined grain microstructure in C31H64 crystals and nanoscale domains of chain-ordered lamellae within these grains. Moreover, nematic phases and dynamical disorder coexist with the domains of ordered lamellae. C30H61OH exhibits more disordered chain packing with no grain structure or lamellar domains. Binary mixtures from 0–50% C30H61OH exhibit a loss of grain structure with increasing alcohol content accompanied by increasingly nematic rather than lamellar chain packing, suggesting a partial but limited solid solution behavior. Together, these results unveil the previously unseen microstructural features governing flexibility and permeability in leaf waxes and outline an approach to microstructure analysis across agrochemicals, pharmaceuticals, and food.
|
Dec 2024
|
|
E02-JEM ARM 300CF
|
Diamond Proposal Number(s):
[33068]
Abstract: In conclusion, this work demonstrates the powerful nature of SED, combined with 3D-ED, to explore sub-crystal nanostructures and defects in beam-sensitive soft materials.
|
Jul 2024
|
|
E02-JEM ARM 300CF
|
Chao
Sun
,
Christopher M.
Pask
,
Sang T.
Pham
,
Emilio
Rapaccioli
,
Andrew J.
Britton
,
Stuart
Micklethwaite
,
Andrew
Bell
,
Maximilian O.
Besenhard
,
Rik
Drummond-Brydson
,
Ke-Jun
Wu
,
Sean M.
Collins
Diamond Proposal Number(s):
[33373]
Open Access
Abstract: The functional group-directed structures of coordination polymers (CPs) and metal–organic frameworks (MOFs) have made them key candidates for proton exchange membranes in fuel cell technologies. Sulfonate group chemistry is well established in proton conducting polymers but has seen less exploration in CPs. Here, we report solvent-directed crystal structures of Cu2+ and Ca2+ CPs constructed with naphthalenedisulfonate (NDS) and anthraquinone-1,5-disulfonate (ADS) ligands, and we correlate single crystal structures across this set with proton conductivities determined by electrochemical impedance spectroscopy. Starting from the Cu2+-based NDS and aminotriazolate MOF designated Cu-SAT and the aqueous synthesis of the known Ca2+-NDS structure incorporating water ligands, we now report a further five sulfonate CP structures. These syntheses include a direct synthesis of the primary degradation product of Cu-SAT in water, solvent-substituted Ca-NDS structures prepared using dimethylformamide and dimethylsulfoxide solvents, and ADS variants of Cu-SAT and Ca-NDS. We demonstrate a consistent 2D layer motif in the NDS CPs, while structural modifications introduced by the ADS ligand result in a 2D hydrogen bonding network with Cu2+ and aminotriazolate ligands and a 1D CP with Ca2+ in water. Proton conductivities across the set span 10−4 to >10−3 S cm−1 at 80 °C and 95% RH. These findings reveal an experimental structure–function relationship between proton conductivity and the tortuosity of the hydrogen bonding network and establish a general, cross-structure descriptor for tuning the sulfonate CP unit cell to systematically modulate proton conductivity.
|
Jun 2024
|
|
E02-JEM ARM 300CF
I07-Surface & interface diffraction
|
Affan N.
Iqbal
,
Kieran W. P.
Orr
,
Satyawan
Nagane
,
Jordi Ferrer
Orri
,
Tiarnan A. S.
Doherty
,
Young-Kwang
Jung
,
Yu-Hsien
Chiang
,
Thomas A.
Selby
,
Yang
Lu
,
Alessandro J.
Mirabelli
,
Alan
Baldwin
,
Zher Ying
Ooi
,
Qichun
Gu
,
Miguel
Anaya
,
Samuel D.
Stranks
Diamond Proposal Number(s):
[32007]
Open Access
Abstract: Halide perovskites are excellent candidate materials for use in solar cell, LED, and detector devices, in part because their composition can be tuned to achieve ideal optoelectronic properties. Empirical efficiency optimisation has led the field towards compositions rich in FA (formamidinium) on the A-site and I on the X-site, with additional small amounts of MA (methylammonium) or Cs A-site cations and Br X-site anions. However, it is not clear how and why the specific compositions of alloyed, i.e., mixed component, halide perovskites relate to photo-stability of the materials. Here, we combine synchrotron grazing incidence wide-angle x-ray scattering, photoluminescence, high-resolution scanning electron diffraction measurements and theoretical modelling to reveal the links between material structure and photostability. Namely, we find that increased octahedral titling leads to improved photo-stability that is correlated with lower densities of performance-harming hexagonal polytype impurities. Our results uncover the structural signatures underpinning photo-stability and can therefore be used to make targeted changes to halide perovskites, bettering the commercial prospects of technologies based on these materials.
|
May 2024
|
|
E02-JEM ARM 300CF
|
Jiajia
Suo
,
Bowen
Yang
,
Edoardo
Mosconi
,
Dmitry
Bogachuk
,
Tiarnan A. S.
Doherty
,
Kyle
Frohna
,
Dominik J.
Kubicki
,
Fan
Fu
,
Yeonju
Kim
,
Oussama
Er-Raji
,
Tiankai
Zhang
,
Lorenzo
Baldinelli
,
Lukas
Wagner
,
Ayodhya N.
Tiwari
,
Feng
Gao
,
Andreas
Hinsch
,
Samuel D.
Stranks
,
Filippo
De Angelis
,
Anders
Hagfeldt
Diamond Proposal Number(s):
[30750]
Open Access
Abstract: The stabilization of grain boundaries and surfaces of the perovskite layer is critical to extend the durability of perovskite solar cells. Here we introduced a sulfonium-based molecule, dimethylphenethylsulfonium iodide (DMPESI), for the post-deposition treatment of formamidinium lead iodide perovskite films. The treated films show improved stability upon light soaking and remains in the black α phase after two years ageing under ambient condition without encapsulation. The DMPESI-treated perovskite solar cells show less than 1% performance loss after more than 4,500 h at maximum power point tracking, yielding a theoretical T80 of over nine years under continuous 1-sun illumination. The solar cells also display less than 5% power conversion efficiency drops under various ageing conditions, including 100 thermal cycles between 25 °C and 85 °C and an 1,050-h damp heat test.
|
Jan 2024
|
|
