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Caiazzo A, Maufort A, van Gorkom BT, Remmerswaal WHM, Orri JF, Li J, Wang J, van Gompel WTM, Van Hecke K, Kusch G, Oliver RA, Ducati C, Lutsen L, Wienk MM, Stranks SD, Vanderzande D, Janssen RAJ. 3D Perovskite Passivation with a Benzotriazole-Based 2D Interlayer for High-Efficiency Solar Cells. ACS APPLIED ENERGY MATERIALS 2023; 6:3933-3943. [PMID: 37064411 PMCID: PMC10091350 DOI: 10.1021/acsaem.3c00101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 03/15/2023] [Indexed: 06/19/2023]
Abstract
2H-Benzotriazol-2-ylethylammonium bromide and iodide and its difluorinated derivatives are synthesized and employed as interlayers for passivation of formamidinium lead triiodide (FAPbI3) solar cells. In combination with PbI2 and PbBr2, these benzotriazole derivatives form two-dimensional (2D) Ruddlesden-Popper perovskites (RPPs) as evidenced by their crystal structures and thin film characteristics. When used to passivate n-i-p FAPbI3 solar cells, the power conversion efficiency improves from 20% to close to 22% by enhancing the open-circuit voltage. Quasi-Fermi level splitting experiments and scanning electron microscopy cathodoluminescence hyperspectral imaging reveal that passivation provides a reduced nonradiative recombination at the interface between the perovskite and hole transport layer. Photoluminescence spectroscopy, angle-resolved grazing-incidence wide-angle X-ray scattering, and depth profiling X-ray photoelectron spectroscopy studies of the 2D/three-dimensional (3D) interface between the benzotriazole RPP and FAPbI3 show that a nonuniform layer of 2D perovskites is enough to passivate defects, enhance charge extraction, and decrease nonradiative recombination.
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Sun Y, Ge L, Dai L, Cho C, Ferrer Orri J, Ji K, Zelewski SJ, Liu Y, Mirabelli AJ, Zhang Y, Huang JY, Wang Y, Gong K, Lai MC, Zhang L, Yang D, Lin J, Tennyson EM, Ducati C, Stranks SD, Cui LS, Greenham NC. Bright and stable perovskite light-emitting diodes in the near-infrared range. Nature 2023; 615:830-835. [PMID: 36922588 DOI: 10.1038/s41586-023-05792-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 02/03/2023] [Indexed: 03/17/2023]
Abstract
Perovskite light-emitting diodes (LEDs) have attracted broad attention due to their rapidly increasing external quantum efficiencies (EQEs)1-15. However, most high EQEs of perovskite LEDs are reported at low current densities (<1 mA cm-2) and low brightness. Decrease in efficiency and rapid degradation at high brightness inhibit their practical applications. Here, we demonstrate perovskite LEDs with exceptional performance at high brightness, achieved by the introduction of a multifunctional molecule that simultaneously removes non-radiative regions in the perovskite films and suppresses luminescence quenching of perovskites at the interface with charge-transport layers. The resulting LEDs emit near-infrared light at 800 nm, show a peak EQE of 23.8% at 33 mA cm-2 and retain EQEs more than 10% at high current densities of up to 1,000 mA cm-2. In pulsed operation, they retain EQE of 16% at an ultrahigh current density of 4,000 mA cm-2, along with a high radiance of more than 3,200 W s-1 m-2. Notably, an operational half-lifetime of 32 h at an initial radiance of 107 W s-1 m-2 has been achieved, representing the best stability for perovskite LEDs having EQEs exceeding 20% at high brightness levels. The demonstration of efficient and stable perovskite LEDs at high brightness is an important step towards commercialization and opens up new opportunities beyond conventional LED technologies, such as perovskite electrically pumped lasers.
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Boehme S, Bodnarchuk MI, Burian M, Bertolotti F, Cherniukh I, Bernasconi C, Zhu C, Erni R, Amenitsch H, Naumenko D, Andrusiv H, Semkiv N, John RA, Baldwin A, Galkowski K, Masciocchi N, Stranks SD, Rainò G, Guagliardi A, Kovalenko MV. Strongly Confined CsPbBr 3 Quantum Dots as Quantum Emitters and Building Blocks for Rhombic Superlattices. ACS NANO 2023; 17:2089-2100. [PMID: 36719353 PMCID: PMC9933619 DOI: 10.1021/acsnano.2c07677] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 01/05/2023] [Indexed: 06/18/2023]
Abstract
The success of the colloidal semiconductor quantum dots (QDs) field is rooted in the precise synthetic control of QD size, shape, and composition, enabling electronically well-defined functional nanomaterials that foster fundamental science and motivate diverse fields of applications. While the exploitation of the strong confinement regime has been driving commercial and scientific interest in InP or CdSe QDs, such a regime has still not been thoroughly explored and exploited for lead-halide perovskite QDs, mainly due to a so far insufficient chemical stability and size monodispersity of perovskite QDs smaller than about 7 nm. Here, we demonstrate chemically stable strongly confined 5 nm CsPbBr3 colloidal QDs via a postsynthetic treatment employing didodecyldimethylammonium bromide ligands. The achieved high size monodispersity (7.5% ± 2.0%) and shape-uniformity enables the self-assembly of QD superlattices with exceptional long-range order, uniform thickness, an unusual rhombic packing with an obtuse angle of 104°, and narrow-band cyan emission. The enhanced chemical stability indicates the promise of strongly confined perovskite QDs for solution-processed single-photon sources, with single QDs showcasing a high single-photon purity of 73% and minimal blinking (78% "on" fraction), both at room temperature.
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Senanayak SP, Dey K, Shivanna R, Li W, Ghosh D, Zhang Y, Roose B, Zelewski SJ, Andaji-Garmaroudi Z, Wood W, Tiwale N, MacManus-Driscoll JL, Friend RH, Stranks SD, Sirringhaus H. Charge transport in mixed metal halide perovskite semiconductors. NATURE MATERIALS 2023; 22:216-224. [PMID: 36702888 DOI: 10.1038/s41563-022-01448-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 11/24/2022] [Indexed: 06/18/2023]
Abstract
Investigation of the inherent field-driven charge transport behaviour of three-dimensional lead halide perovskites has largely remained challenging, owing to undesirable ionic migration effects near room temperature and dipolar disorder instabilities prevalent specifically in methylammonium-and-lead-based high-performing three-dimensional perovskite compositions. Here, we address both these challenges and demonstrate that field-effect transistors based on methylammonium-free, mixed metal (Pb/Sn) perovskite compositions do not suffer from ion migration effects as notably as their pure-Pb counterparts and reliably exhibit hysteresis-free p-type transport with a mobility reaching 5.4 cm2 V-1 s-1. The reduced ion migration is visualized through photoluminescence microscopy under bias and is manifested as an activated temperature dependence of the field-effect mobility with a low activation energy (~48 meV) consistent with the presence of the shallow defects present in these materials. An understanding of the long-range electronic charge transport in these inherently doped mixed metal halide perovskites will contribute immensely towards high-performance optoelectronic devices.
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Liu Y, Banon JP, Frohna K, Chiang YH, Tumen-Ulzii G, Stranks SD, Filoche M, Friend RH. The Electronic Disorder Landscape of Mixed Halide Perovskites. ACS ENERGY LETTERS 2023; 8:250-258. [PMID: 36660372 PMCID: PMC9841609 DOI: 10.1021/acsenergylett.2c02352] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 11/23/2022] [Indexed: 05/13/2023]
Abstract
Band gap tunability of lead mixed halide perovskites makes them promising candidates for various applications in optoelectronics. Here we use the localization landscape theory to reveal that the static disorder due to iodide:bromide compositional alloying contributes at most 3 meV to the Urbach energy. Our modeling reveals that the reason for this small contribution is due to the small effective masses in perovskites, resulting in a natural length scale of around 20 nm for the "effective confining potential" for electrons and holes, with short-range potential fluctuations smoothed out. The increase in Urbach energy across the compositional range agrees well with our optical absorption measurements. We model systems of sizes up to 80 nm in three dimensions, allowing us to accurately reproduce the experimentally observed absorption spectra of perovskites with halide segregation. Our results suggest that we should look beyond static contribution and focus on the dynamic temperature dependent contribution to the Urbach energy.
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Moseley OI, Roose B, Zelewski SJ, Kahmann S, Dey K, Stranks SD. Tunable Multiband Halide Perovskite Tandem Photodetectors with Switchable Response. ACS PHOTONICS 2022; 9:3958-3966. [PMID: 36573164 PMCID: PMC9782784 DOI: 10.1021/acsphotonics.2c01328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Indexed: 06/17/2023]
Abstract
Photodetectors with multiple spectral response bands have shown promise to improve imaging and communications through the switchable detection of different photon energies. However, demonstrations to date have been limited to only two bands and lack capability for fast switching in situ. Here, we exploit the band gap tunability and capability of all-perovskite tandem solar cells to demonstrate a new device concept realizing four spectral bands of response from a single multijunction device, with fast, optically controlled switching between the bands. The response to monochromatic light is highly selective and narrowband without the need for additional filters and switches to broader response bands on applying bias light. Sensitive photodetection above 6 × 1011 Jones is demonstrated in all modes, with rapid switching response times of <250 ns. We demonstrate proof of principle on how the manipulation of the modular multiband detector response through light conditions enables diverse applications in optical communications with secure encryption.
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Kahmann S, Meggiolaro D, Gregori L, Tekelenburg EK, Pitaro M, Stranks SD, De Angelis F, Loi MA. The Origin of Broad Emission in ⟨100⟩ Two-Dimensional Perovskites: Extrinsic vs Intrinsic Processes. ACS ENERGY LETTERS 2022; 7:4232-4241. [PMID: 36531144 PMCID: PMC9745793 DOI: 10.1021/acsenergylett.2c02123] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 10/28/2022] [Indexed: 06/15/2023]
Abstract
2D metal halide perovskites can show narrow and broad emission bands (BEs), and the latter's origin is hotly debated. A widespread opinion assigns BEs to the recombination of intrinsic self-trapped excitons (STEs), whereas recent studies indicate they can have an extrinsic defect-related origin. Here, we carry out a combined experimental-computational study into the microscopic origin of BEs for a series of prototypical phenylethylammonium-based 2D perovskites, comprising different metals (Pb, Sn) and halides (I, Br, Cl). Photoluminescence spectroscopy reveals that all of the compounds exhibit BEs. Where not observable at room temperature, the BE signature emerges upon cooling. By means of DFT calculations, we demonstrate that emission from halide vacancies is compatible with the experimentally observed features. Emission from STEs may only contribute to the BE in the wide-band-gap Br- and Cl-based compounds. Our work paves the way toward a complete understanding of broad emission bands in halide perovskites that will facilitate the fabrication of efficient narrow and white light emitting devices.
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Cho C, Feldmann S, Yeom KM, Jang YW, Kahmann S, Huang JY, Yang TCJ, Khayyat MNT, Wu YR, Choi M, Noh JH, Stranks SD, Greenham NC. Efficient vertical charge transport in polycrystalline halide perovskites revealed by four-dimensional tracking of charge carriers. NATURE MATERIALS 2022; 21:1388-1395. [PMID: 36396960 DOI: 10.1038/s41563-022-01395-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 10/03/2022] [Indexed: 06/16/2023]
Abstract
Fast diffusion of charge carriers is crucial for efficient charge collection in perovskite solar cells. While lateral transient photoluminescence microscopies have been popularly used to characterize charge diffusion in perovskites, there exists a discrepancy between low diffusion coefficients measured and near-unity charge collection efficiencies achieved in practical solar cells. Here, we reveal hidden microscopic dynamics in halide perovskites through four-dimensional (directions x, y and z and time t) tracking of charge carriers by characterizing out-of-plane diffusion of charge carriers. By combining this approach with confocal microscopy, we discover a strong local heterogeneity of vertical charge diffusivities in a three-dimensional perovskite film, arising from the difference between intragrain and intergrain diffusion. We visualize that most charge carriers are efficiently transported through the direct intragrain pathways or via indirect detours through nearby areas with fast diffusion. The observed anisotropy and heterogeneity of charge carrier diffusion in perovskites rationalize their high performance as shown in real devices. Our work also foresees that further control of polycrystal growth will enable solar cells with micrometres-thick perovskites to achieve both long optical path length and efficient charge collection simultaneously.
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Kahmann S, Duim H, Rommens AJ, Frohna K, Ten Brink GH, Portale G, Stranks SD, Loi MA. Taking a closer look - how the microstructure of Dion-Jacobson perovskites governs their photophysics. JOURNAL OF MATERIALS CHEMISTRY. C 2022; 10:17539-17549. [PMID: 36561307 PMCID: PMC9714182 DOI: 10.1039/d2tc04406d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 11/10/2022] [Indexed: 06/17/2023]
Abstract
Scarce information is available on the thin film morphology of Dion-Jacobson halide perovskites. However, the microstructure can have a profound impact on a material's photophysics and its potential for optoelectronic applications. The microscopic mechanisms at play in the prototypical 1,4-phenylenedimethanammonium lead iodide (PDMAPbI4) Dion-Jacobson compound are here elucidated through a combination of hyperspectral photoluminescence and Raman spectro-microscopy supported by x-ray diffraction. In concert, these techniques allow for a detailed analysis of local composition and microstructure. PDMAPbI4 thin films are shown to be phase-pure and to form micron-sized crystallites with a dominant out-of-plane stacking and strong in-plane rotational disorder. Sample topography, localised defects, and a strong impact of temperature-variation create a complex and heterogeneous picture of the luminescence that cannot be captured by a simplified bulk-semiconductor picture. Our study highlights the power of optical microscopy techniques used in combination, and underlines the danger of conceptual oversimplification when analysing the photophysics of perovskite thin films.
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Ruggeri E, Anaya M, Gałkowski K, Abfalterer A, Chiang YH, Ji K, Andaji-Garmaroudi Z, Stranks SD. Halide Remixing under Device Operation Imparts Stability on Mixed-Cation Mixed-Halide Perovskite Solar Cells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2202163. [PMID: 35866352 DOI: 10.1002/adma.202202163] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 07/11/2022] [Indexed: 06/15/2023]
Abstract
Mixed-halide mixed-cation hybrid perovskites are among the most promising perovskite compositions for application in a variety of optoelectronic devices due to their high performance, low cost, and bandgap-tuning capabilities. Instability pathways such as those driven by ionic migration, however, continue to hinder their further progress. Here, an operando variable-pitch synchrotron grazing-incidence wide-angle X-ray scattering technique is used to track the surface and bulk structural changes in mixed-halide mixed-cation perovskite solar cells under continuous load and illumination. By monitoring the evolution of the material structure, it is demonstrated that halide remixing along the electric field and illumination direction during operation hinders phase segregation and limits device instability. Correlating the evolution with directionality- and depth-dependent analyses, it is proposed that this halide remixing is induced by an electrostrictive effect acting along the substrate out-of-plane direction. However, this stabilizing effect is overwhelmed by competing halide demixing processes in devices exposed to humid air or with poorer starting performance. The findings shed new light on understanding halide de- and re-mixing competitions and their impact on device longevity. These operando techniques allow real-time tracking of the structural evolution in full optoelectronic devices and unveil otherwise inaccessible insights into rapid structural evolution under external stress conditions.
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Otero‐Martínez C, Imran M, Schrenker NJ, Ye J, Ji K, Rao A, Stranks SD, Hoye RLZ, Bals S, Manna L, Pérez‐Juste J, Polavarapu L. Fast A‐Site Cation Cross‐Exchange at Room Temperature: Single‐to Double‐ and Triple‐Cation Halide Perovskite Nanocrystals. Angew Chem Int Ed Engl 2022; 61:e202205617. [PMID: 35748492 PMCID: PMC9540746 DOI: 10.1002/anie.202205617] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Indexed: 11/20/2022]
Abstract
We report here fast A‐site cation cross‐exchange between APbX3 perovskite nanocrystals (NCs) made of different A‐cations (Cs (cesium), FA (formamidinium), and MA (methylammonium)) at room temperature. Surprisingly, the A‐cation cross‐exchange proceeds as fast as the halide (X=Cl, Br, or I) exchange with the help of free A‐oleate complexes present in the freshly prepared colloidal perovskite NC solutions. This enabled the preparation of double (MACs, MAFA, CsFA)‐ and triple (MACsFA)‐cation perovskite NCs with an optical band gap that is finely tunable by their A‐site composition. The optical spectroscopy together with structural analysis using XRD and atomically resolved high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) and integrated differential phase contrast (iDPC) STEM indicates the homogeneous distribution of different cations in the mixed perovskite NC lattice. Unlike halide ions, the A‐cations do not phase‐segregate under light illumination.
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Ye J, Li Z, Kubicki DJ, Zhang Y, Dai L, Otero-Martínez C, Reus MA, Arul R, Dudipala KR, Andaji-Garmaroudi Z, Huang YT, Li Z, Chen Z, Müller-Buschbaum P, Yip HL, Stranks SD, Grey CP, Baumberg JJ, Greenham NC, Polavarapu L, Rao A, Hoye RLZ. Elucidating the Role of Antisolvents on the Surface Chemistry and Optoelectronic Properties of CsPbBr xI 3-x Perovskite Nanocrystals. J Am Chem Soc 2022; 144:12102-12115. [PMID: 35759794 PMCID: PMC9284547 DOI: 10.1021/jacs.2c02631] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
Colloidal lead-halide
perovskite nanocrystals (LHP NCs) have emerged
over the past decade as leading candidates for efficient next-generation
optoelectronic devices, but their properties and performance critically
depend on how they are purified. While antisolvents are widely used
for purification, a detailed understanding of how the polarity of
the antisolvent influences the surface chemistry and composition of
the NCs is missing in the field. Here, we fill this knowledge gap
by
studying the surface chemistry of purified CsPbBrxI3-x NCs as the model system,
which in itself is considered a promising candidate for pure-red light-emitting
diodes and top-cells for tandem photovoltaics. Interestingly, we find
that as the polarity of the antisolvent increases (from methyl acetate
to acetone to butanol), there is a blueshift in the photoluminescence
(PL) peak of the NCs along with a decrease in PL quantum yield (PLQY).
Through transmission electron microscopy and X-ray photoemission spectroscopy
measurements, we find that these changes in PL properties arise from
antisolvent-induced iodide removal, which leads to a change in halide
composition and, thus, the bandgap. Using detailed nuclear magnetic
resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR)
measurements along with density functional theory calculations, we
propose that more polar antisolvents favor the detachment of the oleic
acid and oleylamine ligands, which undergo amide condensation reactions,
leading to the removal of iodide anions from the NC surface bound
to these ligands. This work shows that careful selection of low-polarity
antisolvents is a critical part of designing the synthesis of NCs
to achieve high PLQYs with minimal defect-mediated phase segregation.
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Otero-Martínez C, Imran M, Schrenker NJ, Ye J, Ji K, Rao A, Stranks SD, Hoye RLZ, Bals S, Manna L, Pérez-Juste J, Polavarapu L. Fast A‐Site Cation Cross‐exchange at Room Temperature: Single‐to Double‐ and Triple‐Cation Halide Perovskite Nanocrystals. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Bowman AR, Stranks SD, Monserrat B. Investigation of Singlet Fission-Halide Perovskite Interfaces. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2022; 34:4865-4875. [PMID: 35722200 PMCID: PMC9202303 DOI: 10.1021/acs.chemmater.1c04310] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 04/22/2022] [Indexed: 06/15/2023]
Abstract
A method for improving the efficiency of solar cells is combining a low-band-gap semiconductor with a singlet fission material (which converts one high-energy singlet into two low-energy triplets following photoexcitation). Here, we present a study of the interface between singlet fission molecules and low-band-gap halide pervoskites. We briefly present 150 experiments screening for triplet transfer into a halide perovskite. However, in all cases, triplet transfer was not observed. This motivated us to understand the halide perovskite-singlet fission interface better by carrying out first-principles calculations using tetracene and cesium lead iodide. We found that tetracene molecules/thin films preferentially orient themselves parallel to/perpendicular to the halide perovskite's surface. This result is in agreement with simulations of tetracene (and other rodlike molecules) on a wide range of inorganic semiconductors. We present formation energies of all interfaces, which are significantly less favorable than for bulk tetracene, indicative of weak interaction at the interface. It was not possible to calculate excitonic states at the full interface due to computational limitations, so we instead present highly speculative toy interfaces between tetracene and a halide-perovskite-like structure. In these models, we focus on replicating tetracene's electronic states correctly. We find that tetracene's singlet and triplet energies are comparable to that of bulk tetracene, and the triplet is strongly localized on a single tetracene molecule, even at an interface. Our work provides new understanding of the interface between tetracene and halide perovskites, explores the potential for modeling excitons at interfaces, and begins to explain the difficulties in extracting triplets directly into inorganic semiconductors.
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Smith HJ, Purnell BA, Suleymanov Y, Szuromi P, Scanlon ST, VanHook AM, Hodges K, Grocholski B, Zahn LM, Lavine MS, Vignieri S, Funk MA, Charneski CA, Isles HM, Stranks SD. In Science Journals. Science 2022; 376:957-959. [PMID: 35617413 DOI: 10.1126/science.add1423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Highlights from the Science family of journals.
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Macpherson S, Doherty TAS, Winchester AJ, Kosar S, Johnstone DN, Chiang YH, Galkowski K, Anaya M, Frohna K, Iqbal AN, Nagane S, Roose B, Andaji-Garmaroudi Z, Orr KWP, Parker JE, Midgley PA, Dani KM, Stranks SD. Local Nanoscale Phase Impurities are Degradation Sites in Halide Perovskites. Nature 2022; 607:294-300. [PMID: 35609624 DOI: 10.1038/s41586-022-04872-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 05/13/2022] [Indexed: 11/09/2022]
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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Ferrer Orri J, Doherty TAS, Johnstone D, Collins SM, Simons H, Midgley PA, Ducati C, Stranks SD. Unveiling the Interaction Mechanisms of Electron and X-ray Radiation with Halide Perovskite Semiconductors using Scanning Nanoprobe Diffraction. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2200383. [PMID: 35288992 DOI: 10.1002/adma.202200383] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 02/28/2022] [Indexed: 06/14/2023]
Abstract
The interaction of high-energy electrons and X-ray photons with beam-sensitive semiconductors such as halide perovskites is essential for the characterization and understanding of these optoelectronic materials. Using nanoprobe diffraction techniques, which can investigate physical properties on the nanoscale, studies of the interaction of electron and X-ray radiation with state-of-the-art (FA0.79 MA0.16 Cs0.05 )Pb(I0.83 Br0.17 )3 hybrid halide perovskite films (FA, formamidinium; MA, methylammonium) are performed, tracking the changes in the local crystal structure as a function of fluence using scanning electron diffraction and synchrotron nano X-ray diffraction techniques. Perovskite grains are identified, 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. This 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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Du T, Richheimer F, Frohna K, Gasparini N, Mohan L, Min G, Xu W, Macdonald TJ, Yuan H, Ratnasingham SR, Haque S, Castro FA, Durrant JR, Stranks SD, Wood S, McLachlan MA, Briscoe J. Overcoming Nanoscale Inhomogeneities in Thin-Film Perovskites via Exceptional Post-annealing Grain Growth for Enhanced Photodetection. NANO LETTERS 2022; 22:979-988. [PMID: 35061402 PMCID: PMC9007526 DOI: 10.1021/acs.nanolett.1c03839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 01/06/2022] [Indexed: 06/14/2023]
Abstract
Antisolvent-assisted spin coating has been widely used for fabricating metal halide perovskite films with smooth and compact morphology. However, localized nanoscale inhomogeneities exist in these films owing to rapid crystallization, undermining their overall optoelectronic performance. Here, we show that by relaxing the requirement for film smoothness, outstanding film quality can be obtained simply through a post-annealing grain growth process without passivation agents. The morphological changes, driven by a vaporized methylammonium chloride (MACl)-dimethylformamide (DMF) solution, lead to comprehensive defect elimination. Our nanoscale characterization visualizes the local defective clusters in the as-deposited film and their elimination following treatment, which couples with the observation of emissive grain boundaries and excellent inter- and intragrain optoelectronic uniformity in the polycrystalline film. Overcoming these performance-limiting inhomogeneities results in the enhancement of the photoresponse to low-light (<0.1 mW cm-2) illumination by up to 40-fold, yielding high-performance photodiodes with superior low-light detection.
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Kosasih FU, Divitini G, Orri JF, Tennyson EM, Kusch G, Oliver RA, Stranks SD, Ducati C. Optical emission from focused ion beam milled halide perovskite device cross-sections. Microsc Res Tech 2022; 85:2351-2355. [PMID: 35118749 PMCID: PMC9304233 DOI: 10.1002/jemt.24069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 01/13/2022] [Accepted: 01/17/2022] [Indexed: 02/04/2023]
Abstract
Cross-sectional transmission electron microscopy has been widely used to investigate organic-inorganic hybrid halide perovskite-based optoelectronic devices. Electron-transparent specimens (lamellae) used in such studies are often prepared using focused ion beam (FIB) milling. However, the gallium ions used in FIB milling may severely degrade the structure and composition of halide perovskites in the lamellae, potentially invalidating studies performed on them. In this work, the close relationship between perovskite structure and luminescence is exploited to examine the structural quality of perovskite solar cell lamellae prepared by FIB milling. Through hyperspectral cathodoluminescence (CL) mapping, the perovskite layer was found to remain optically active with a slightly blue-shifted luminescence. This finding indicates that the perovskite structure is largely preserved upon the lamella fabrication process although some surface amorphisation occurred. Further changes in CL due to electron beam irradiation were also recorded, confirming that electron dose management is essential in electron microscopy studies of carefully prepared halide perovskite-based device lamellae.
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Frohna K, Anaya M, Macpherson S, Sung J, Doherty TAS, Chiang YH, Winchester AJ, Orr KWP, Parker JE, Quinn PD, Dani KM, Rao A, Stranks SD. Nanoscale chemical heterogeneity dominates the optoelectronic response of alloyed perovskite solar cells. NATURE NANOTECHNOLOGY 2022; 17:190-196. [PMID: 34811554 DOI: 10.1038/s41565-021-01019-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 09/29/2021] [Indexed: 05/24/2023]
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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46
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Zanetta A, Andaji-Garmaroudi Z, Pirota V, Pica G, Kosasih FU, Gouda L, Frohna K, Ducati C, Doria F, Stranks SD, Grancini G. Manipulating Color Emission in 2D Hybrid Perovskites by Fine Tuning Halide Segregation: A Transparent Green Emitter. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2105942. [PMID: 34658076 DOI: 10.1002/adma.202105942] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/10/2021] [Indexed: 06/13/2023]
Abstract
Halide perovskite materials offer an ideal playground for easily tuning their color and, accordingly, the spectral range of their emitted light. In contrast to common procedures, this work demonstrates that halide substitution in Ruddlesden-Popper perovskites not only progressively modulates the bandgap, but it can also be a powerful tool to control the nanoscale phase segregation-by adjusting the halide ratio and therefore the spatial distribution of recombination centers. As a result, thin films of chloride-rich perovskite are engineered-which appear transparent to the human eye-with controlled tunable emission in the green. This is due to a rational halide substitution with iodide or bromide leading to a spatial distribution of phases where the minor component is responsible for the tunable emission, as identified by combined hyperspectral photoluminescence imaging and elemental mapping. This work paves the way for the next generation of highly tunable transparent emissive materials, which can be used as light-emitting pixels in advanced and low-cost optoelectronics.
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Doherty TAS, Nagane S, Kubicki DJ, Jung YK, Johnstone DN, Iqbal AN, Guo D, Frohna K, Danaie M, Tennyson EM, Macpherson S, Abfalterer A, Anaya M, Chiang YH, Crout P, Ruggeri FS, Collins S, Grey CP, Walsh A, Midgley PA, Stranks SD. Stabilized tilted-octahedra halide perovskites inhibit local formation of performance-limiting phases. Science 2021; 374:1598-1605. [PMID: 34941391 DOI: 10.1126/science.abl4890] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
[Figure: see text].
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Kosar S, Winchester AJ, Doherty TAS, Macpherson S, Petoukhoff CE, Frohna K, Anaya M, Chan NS, Madéo J, Man MKL, Stranks SD, Dani KM. Unraveling the varied nature and roles of defects in hybrid halide perovskites with time-resolved photoemission electron microscopy. ENERGY & ENVIRONMENTAL SCIENCE 2021; 14:6320-6328. [PMID: 35003331 PMCID: PMC8658252 DOI: 10.1039/d1ee02055b] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Accepted: 09/01/2021] [Indexed: 06/14/2023]
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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Krajewska CJ, Kavanagh SR, Zhang L, Kubicki DJ, Dey K, Gałkowski K, Grey CP, Stranks SD, Walsh A, Scanlon DO, Palgrave RG. Enhanced visible light absorption in layered Cs 3Bi 2Br 9 through mixed-valence Sn(ii)/Sn(iv) doping. Chem Sci 2021; 12:14686-14699. [PMID: 34820084 PMCID: PMC8597838 DOI: 10.1039/d1sc03775g] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 10/04/2021] [Indexed: 11/21/2022] Open
Abstract
Lead-free halides with perovskite-related structures, such as the vacancy-ordered perovskite Cs3Bi2Br9, are of interest for photovoltaic and optoelectronic applications. We find that addition of SnBr2 to the solution-phase synthesis of Cs3Bi2Br9 leads to substitution of up to 7% of the Bi(iii) ions by equal quantities of Sn(ii) and Sn(iv). The nature of the substitutional defects was studied by X-ray diffraction, 133Cs and 119Sn solid state NMR, X-ray photoelectron spectroscopy and density functional theory calculations. The resulting mixed-valence compounds show intense visible and near infrared absorption due to intervalence charge transfer, as well as electronic transitions to and from localised Sn-based states within the band gap. Sn(ii) and Sn(iv) defects preferentially occupy neighbouring B-cation sites, forming a double-substitution complex. Unusually for a Sn(ii) compound, the material shows minimal changes in optical and structural properties after 12 months storage in air. Our calculations suggest the stabilisation of Sn(ii) within the double substitution complex contributes to this unusual stability. These results expand upon research on inorganic mixed-valent halides to a new, layered structure, and offer insights into the tuning, doping mechanisms, and structure-property relationships of lead-free vacancy-ordered perovskite structures.
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Yuan S, Cui LS, Dai L, Liu Y, Liu QW, Sun YQ, Auras F, Anaya M, Zheng X, Ruggeri E, Yu YJ, Qu YK, Abdi-Jalebi M, Bakr OM, Wang ZK, Stranks SD, Greenham NC, Liao LS, Friend RH. Efficient and Spectrally Stable Blue Perovskite Light-Emitting Diodes Employing a Cationic π-Conjugated Polymer. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2103640. [PMID: 34558117 DOI: 10.1002/adma.202103640] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 08/22/2021] [Indexed: 06/13/2023]
Abstract
Metal halide perovskite semiconductors have demonstrated remarkable potentials in solution-processed blue light-emitting diodes (LEDs). However, the unsatisfied efficiency and spectral stability responsible for trap-mediated non-radiative losses and halide phase segregation remain the primary unsolved challenges for blue perovskite LEDs. In this study, it is reported that a fluorene-based π-conjugated cationic polymer can be blended with the perovskite semiconductor to control film formation and optoelectronic properties. As a result, sky-blue and true-blue perovskite LEDs with Commission Internationale de l'Eclairage coordinates of (0.08, 0.22) and (0.12, 0.13) at the record external quantum efficiencies of 11.2% and 8.0% were achieved. In addition, the mixed halide perovskites with the conjugated cationic polymer exhibit excellent spectral stability under external bias. This result illustrates that π-conjugated cationic polymers have a great potential to realize efficient blue mixed-halide perovskite LEDs with stable electroluminescence.
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