B21-High Throughput SAXS
labSAXS-Offline SAXS and Sample Environment Development
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Diamond Proposal Number(s):
[29568, 30717, 30473]
Open Access
Abstract: The instability and limited scalability of halide perovskites hinder their long-term viability in applications as X-ray detectors. Here, we introduce a sol-gel ship-in-bottle approach to produce a monolithic perovskite@metal-organic framework (MOF) composite, combining the properties of the individual building blocks and enhancing density, robustness, and stability. By tuning seed particles below 100 nm, we achieve highly crystalline, dense composites with up to 40% perovskite loading. Structural and optical characterization unveils perovskite nanocrystals forming within MOF mesopores, maximizing stability and preventing degradation, maintaining over 90% photoluminescence and structural integrity after weeks of exposure to humidity, heat, and solvents. Proposed as an innovative class of scintillator, these monolithic perovskite@MOFs attenuate X-rays efficiently and exhibit outstanding stability under high radiation doses equivalent to 110,000 typical chest X-rays, with a radioluminescence lifetime of 10 ns, outperforming commercial scintillators. This approach offers vast potential for developing high-performance, cost-effective, and stable devices for radiation detection and other optoelectronic applications.
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Sep 2024
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E02-JEM ARM 300CF
I07-Surface & interface diffraction
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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.
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May 2024
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E02-JEM ARM 300CF
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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.
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Jan 2024
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I13-1-Coherence
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Kieran W. P.
Orr
,
Jiecheng
Diao
,
Muhammad Naufal
Lintangpradipto
,
Darren J.
Batey
,
Affan N.
Iqbal
,
Simon
Kahmann
,
Kyle
Frohna
,
Milos
Dubajic
,
Szymon J.
Zelewski
,
Alice E.
Dearle
,
Thomas A.
Selby
,
Peng
Li
,
Tiarnan A. S.
Doherty
,
Stephan
Hofmann
,
Osman M.
Bakr
,
Ian K.
Robinson
,
Samuel D.
Stranks
Diamond Proposal Number(s):
[25097, 28495, 30308]
Open Access
Abstract: In recent years, halide perovskite materials have been used to make high performance solar cell and light-emitting devices. However, material defects still limit device performance and stability. Here, we use synchrotron-based Bragg Coherent Diffraction Imaging to visualise nanoscale strain fields, such as those local to defects, in halide perovskite microcrystals. We find significant strain heterogeneity within MAPbBr3 (MA = CH3NH3+) crystals in spite of their high optoelectronic quality, and identify both 〈100〉 and 〈110〉 edge dislocations through analysis of their local strain fields. By imaging these defects and strain fields in situ under continuous illumination, we uncover dramatic light-induced dislocation migration across hundreds of nanometers. Further, by selectively studying crystals that are damaged by the X-ray beam, we correlate large dislocation densities and increased nanoscale strains with material degradation and substantially altered optoelectronic properties assessed using photoluminescence microscopy measurements. Our results demonstrate the dynamic nature of extended defects and strain in halide perovskites, which will have important consequences for device performance and operational stability.
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Sep 2023
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E02-JEM ARM 300CF
I14-Hard X-ray Nanoprobe
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Stuart
Macpherson
,
Tiarnan A. S.
Doherty
,
Andrew J.
Winchester
,
Sofiia
Kosar
,
Duncan N.
Johnstone
,
Yu-Hsien
Chiang
,
Krzysztof
Galkowski
,
Miguel
Anaya
,
Kyle
Frohna
,
Affan N.
Iqbal
,
Satyawan
Nagane
,
Bart
Roose
,
Zahra
Andaji-Garmaroudi
,
Kieran W. P.
Orr
,
Julia E.
Parker
,
Paul A.
Midgley
,
Keshav M.
Dani
,
Samuel D.
Stranks
Diamond Proposal Number(s):
[24111, 20420]
Abstract: Understanding the nanoscopic chemical and structural changes that drive instabilities in emerging energy materials is essential for mitigating device degradation. The power conversion efficiency of halide perovskite photovoltaic devices has reached 25.7% in single junction and 29.8% in tandem perovskite/silicon cells1,2, yet retaining such performance under continuous operation has remained elusive3. Here, we develop a multimodal microscopy toolkit to reveal that in leading formamidinium-rich perovskite absorbers, nanoscale phase impurities including hexagonal polytype and lead iodide inclusions are not only traps for photo-excited carriers which themselves reduce performance4,5, but via the same trapping process are sites at which photochemical degradation of the absorber layer is seeded. We visualise illumination-induced structural changes at phase impurities associated with trap clusters, revealing that even trace amounts of these phases, otherwise undetected with bulk measurements, compromise device longevity. The type and distribution of these unwanted phase inclusions depends on film composition and processing, with the presence of polytypes being most detrimental for film photo-stability. Importantly, we reveal that performance losses and intrinsic degradation processes can both be mitigated by modulating these defective phase impurities, and demonstrate that this requires careful tuning of local structural and chemical properties. This multimodal workflow to correlate the nanoscopic landscape of beam sensitive energy materials will be applicable to a wide range of semiconductors for which a local picture of performance and operational stability has yet to be established.
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May 2022
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E02-JEM ARM 300CF
I14-Hard X-ray Nanoprobe
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Diamond Proposal Number(s):
[25250, 20420]
Open Access
Abstract: The interaction of high-energy electrons and X-ray photons with beam-sensitive semiconductors such as halide perovskites is essential for the characterisation and understanding of these optoelectronic materials. Using nano-probe diffraction techniques, which can investigate physical properties on the nanoscale, we perform studies of the interaction of electron and X-ray radiation with state-of-the-art (FA0.79MA0.16Cs0.05)Pb(I0.83Br0.17)3 hybrid halide perovskite films (FA, formamidinium; MA, methylammonium). We track the changes in the local crystal structure as a function of fluence using scanning electron diffraction and synchrotron nano X-ray diffraction techniques. We identify perovskite grains from which additional reflections, corresponding to PbBr2, appear as a crystalline degradation phase after fluences of ∼200 e–Å–2. These changes are concomitant with the formation of small PbI2 crystallites at the adjacent high-angle grain boundaries, with the formation of pinholes, and with a phase transition from tetragonal to cubic. A similar degradation pathway is caused by photon irradiation in nano-X-ray diffraction, suggesting common underlying mechanisms. Our approach explores the radiation limits of these materials and provides a description of the degradation pathways on the nanoscale. Addressing high-angle grain boundaries will be critical for the further improvement of halide polycrystalline film stability, especially for applications vulnerable to high-energy radiation such as space photovoltaics.
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Mar 2022
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E02-JEM ARM 300CF
I14-Hard X-ray Nanoprobe
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Tiarnan A. S.
Doherty
,
Dominik
Kubicki
,
Stuart
Macpherson
,
Young-Kwang
Jung
,
Duncan
Johnstone
,
Affan
Iqbal
,
Dengyang
Guo
,
Kyle
Frohna
,
Mohsen
Danaie
,
Elizabeth
Tennyson
,
Satyawan
Nagane
,
Anna
Abfalterer
,
Miguel
Anaya
,
Yu-Hsien
Chiang
,
Phillip
Crout
,
Francesco Simone
Ruggeri
,
Sean
Collins
,
Clare
Grey
,
Aron
Walsh
,
Paul
Midgley
,
Samuel
Stranks
Diamond Proposal Number(s):
[20420, 24111]
Abstract: There is currently substantial interest in stabilizing the simple ternary FAPbI3 perovskite because of its near-optimal band gap and superior thermal stability compared to methylammonium-based materials.1 The key challenge of FAPbI3 is the thermodynamic instability of the polymorph required for efficient light harvesting. Without additives, the black photoactive α-polymorph is only stable above ca. 160°C. At room temperature, it is metastable and rapidly transitions to the non-perovskite yellow polymorph. The stabilization of the black polymorph at room temperature can be achieved, for example, by adding a small amount of the pernicious MA through use of methylammonium chloride (in conjunction with formamidinium formate),2 methylammonium thiocyanate,3 or methylammonium formate.4 We have developed a new stabilization strategy which does not involve the addition of MA.5 Instead, it uses a surface-templating agent (EDTA) which modifies the material without incorporating into the structure. We use a combination of scanning electron diffraction (SED) and nuclear magnetic resonance spectroscopies (NMR, NQR) to identify the atomic-level mechanism of action of EDTA in this role. We find that it templates the structure by inducing a small octahedral tilt, only resolvable with local characterization techniques, and imparts remarkable phase stability by arresting transitions to low-dimensional polymorphs. This octahedral tilt engineering strategy is remarkably universal, and we show that it is the intrinsic stabilization mechanism in the state-of-the-art FA-rich mixed-cation materials.
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Feb 2022
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E02-JEM ARM 300CF
I14-Hard X-ray Nanoprobe
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Tiarnan A. S.
Doherty
,
Satyawan
Nagane
,
Dominik J.
Kubicki
,
Young-Kwang
Jung
,
Duncan N.
Johnstone
,
Affan N.
Iqbal
,
Dengyang
Guo
,
Kyle
Frohna
,
Mohsen
Danaie
,
Elizabeth M.
Tennyson
,
Stuart
Macpherson
,
Anna
Abfalterer
,
Miguel
Anaya
,
Yu-Hsien
Chiang
,
Phillip
Crout
,
Francesco Simone
Ruggeri
,
Sean M.
Collins
,
Clare P.
Grey
,
Aron
Walsh
,
Paul A.
Midgley
,
Samuel D.
Stranks
Diamond Proposal Number(s):
[20420, 24111]
Abstract: Efforts to stabilize photoactive formamidinium (FA)–based halide perovskites for perovskite photovoltaics have focused on the growth of cubic formamidinium lead iodide (α-FAPbI3) phases by empirically alloying with cesium, methylammonium (MA) cations, or both. We show that such stabilized FA-rich perovskites are noncubic and exhibit ~2° octahedral tilting at room temperature. This tilting, resolvable only with the use of local nanostructure characterization techniques, imparts phase stability by frustrating transitions from photoactive to hexagonal phases. Although the bulk phase appears stable when examined macroscopically, heterogeneous cation distributions allow microscopically unstable regions to form; we found that these transitioned to hexagonal polytypes, leading to local trap-assisted performance losses and photoinstabilities. Using surface-bound ethylenediaminetetraacetic acid, we engineered an octahedral tilt into pure α-FAPbI3 thin films without any cation alloying. The templated photoactive FAPbI3 film was extremely stable against thermal, environmental, and light stressors.
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Dec 2021
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I14-Hard X-ray Nanoprobe
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Kyle
Frohna
,
Miguel
Anaya
,
Stuart
Macpherson
,
Jooyoung
Sung
,
Tiarnan A. S.
Doherty
,
Yu-Hsien
Chiang
,
Andrew J.
Winchester
,
Kieran W. P.
Orr
,
Julia E.
Parker
,
Paul D.
Quinn
,
Keshav M.
Dani
,
Akshay
Rao
,
Samuel D.
Stranks
Diamond Proposal Number(s):
[19023, 20420]
Abstract: Halide perovskites perform remarkably in optoelectronic devices. However, this exceptional performance is striking given that perovskites exhibit deep charge-carrier traps and spatial compositional and structural heterogeneity, all of which should be detrimental to performance. Here, we resolve this long-standing paradox by providing a global visualization of the nanoscale chemical, structural and optoelectronic landscape in halide perovskite devices, made possible through the development of a new suite of correlative, multimodal microscopy measurements combining quantitative optical spectroscopic techniques and synchrotron nanoprobe measurements. We show that compositional disorder dominates the optoelectronic response over a weaker influence of nanoscale strain variations even of large magnitude. Nanoscale compositional gradients drive carrier funnelling onto local regions associated with low electronic disorder, drawing carrier recombination away from trap clusters associated with electronic disorder and leading to high local photoluminescence quantum efficiency. These measurements reveal a global picture of the competitive nanoscale landscape, which endows enhanced defect tolerance in devices through spatial chemical disorder that outcompetes both electronic and structural disorder.
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Nov 2021
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I14-Hard X-ray Nanoprobe
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Sofiia
Kosar
,
Andrew J.
Winchester
,
Tiarnan A. S.
Doherty
,
Stuart
Macpherson
,
Christopher E.
Petoukhoff
,
Kyle
Frohna
,
Miguel
Anaya
,
Nicholas S.
Chan
,
Julien
Madéo
,
Michael K. L.
Man
,
Samuel D.
Stranks
,
Keshav M.
Dani
Diamond Proposal Number(s):
[19023]
Open Access
Abstract: With rapidly growing photoconversion efficiencies, hybrid perovskite solar cells have emerged as promising contenders for next generation, low-cost photovoltaic technologies. Yet, the presence of nanoscale defect clusters, that form during the fabrication process, remains critical to overall device operation, including efficiency and long-term stability. To successfully deploy hybrid perovskites, we must understand the nature of the different types of defects, assess their potentially varied roles in device performance, and understand how they respond to passivation strategies. Here, by correlating photoemission and synchrotron-based scanning probe X-ray microscopies, we unveil three different types of defect clusters in state-of-the-art triple cation mixed halide perovskite thin films. Incorporating ultrafast time-resolution into our photoemission measurements, we show that defect clusters originating at grain boundaries are the most detrimental for photocarrier trapping, while lead iodide defect clusters are relatively benign. Hexagonal polytype defect clusters are only mildly detrimental individually, but can have a significant impact overall if abundant in occurrence. We also show that passivating defects with oxygen in the presence of light, a previously used approach to improve efficiency, has a varied impact on the different types of defects. Even with just mild oxygen treatment, the grain boundary defects are completely healed, while the lead iodide defects begin to show signs of chemical alteration. Our findings highlight the need for multi-pronged strategies tailored to selectively address the detrimental impact of the different defect types in hybrid perovskite solar cells.
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Sep 2021
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