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  1. Article: Reliably obtaining white light from layered halide perovskites at room temperature.

    Crace, Ethan J / Su, Alexander C / Karunadasa, Hemamala I

    Chemical science

    2022  Volume 13, Issue 34, Page(s) 9973–9979

    Abstract: The recent observation of broadband white-light emission from the inorganic sheets of certain layered lead-bromide perovskites has instigated a multitude of studies on this unusual phenomenon. However, the vast majority of layered bromide perovskites ... ...

    Abstract The recent observation of broadband white-light emission from the inorganic sheets of certain layered lead-bromide perovskites has instigated a multitude of studies on this unusual phenomenon. However, the vast majority of layered bromide perovskites have flat (001) inorganic sheets and display a narrow photoluminescence at room temperature. A handful of heavily distorted (001) perovskites display broad emission, but to date, there is no method of predicting which perovskites will produce white light at room temperature prior to screening different organic molecules that can template 2D perovskites and crystallizing and analyzing the material. By studying ten Pb-Cl perovskites, we find that they all exhibit a broad yellow emission, which is strikingly invariant despite different distortions in the inorganic framework seen across the series. We postulate that this broad emission is intrinsic to all layered Pb-Cl perovskites. Although broad, the emission is not white. By adding Br to the Pb-Cl perovskites we obtain both the narrow emission and the broad emission such that the combined emission color smoothly varies from yellow to warm white to cold white as a function of the halide ratio. Thus, alloying Br to Pb-Cl perovskites appears to be a simple and general strategy for reliably obtaining white light at room temperature from (001) perovskites, regardless of the templating effects of the organic molecules, which should greatly expand the number of white-light-emitting layered perovskites.
    Language English
    Publishing date 2022-08-01
    Publishing country England
    Document type Journal Article
    ZDB-ID 2559110-1
    ISSN 2041-6539 ; 2041-6520
    ISSN (online) 2041-6539
    ISSN 2041-6520
    DOI 10.1039/d2sc02381d
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: Halide Perovskites Breathe Too: The Iodide-Iodine Equilibrium and Self-Doping in Cs

    Vigil, Julian A / Wolf, Nathan R / Slavney, Adam H / Matheu, Roc / Saldivar Valdes, Abraham / Breidenbach, Aaron / Lee, Young S / Karunadasa, Hemamala I

    ACS central science

    2024  Volume 10, Issue 4, Page(s) 907–919

    Abstract: The response of an oxide crystal to the atmosphere can be personified as breathing-a dynamic equilibrium between ... ...

    Abstract The response of an oxide crystal to the atmosphere can be personified as breathing-a dynamic equilibrium between O
    Language English
    Publishing date 2024-04-02
    Publishing country United States
    Document type Journal Article
    ISSN 2374-7943
    ISSN 2374-7943
    DOI 10.1021/acscentsci.4c00056
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: Understanding the evolution of double perovskite band structure upon dimensional reduction.

    Connor, Bridget A / Su, Alexander C / Slavney, Adam H / Leppert, Linn / Karunadasa, Hemamala I

    Chemical science

    2023  Volume 14, Issue 42, Page(s) 11858–11871

    Abstract: Recent investigations into the effects of dimensional reduction on halide double perovskites have revealed an intriguing change in band structure when the three-dimensional (3D) perovskite is reduced to a two-dimensional (2D) perovskite with inorganic ... ...

    Abstract Recent investigations into the effects of dimensional reduction on halide double perovskites have revealed an intriguing change in band structure when the three-dimensional (3D) perovskite is reduced to a two-dimensional (2D) perovskite with inorganic sheets of monolayer thickness (
    Language English
    Publishing date 2023-09-14
    Publishing country England
    Document type Journal Article
    ZDB-ID 2559110-1
    ISSN 2041-6539 ; 2041-6520
    ISSN (online) 2041-6539
    ISSN 2041-6520
    DOI 10.1039/d3sc03105e
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Mosaic Cu

    Li, Jiayi / Matheu, Roc / Ke, Feng / Liu, Zhenxian / Lin, Yu / Karunadasa, Hemamala I

    Angewandte Chemie (International ed. in English)

    2023  Volume 62, Issue 20, Page(s) e202300957

    Abstract: The perovskite (BA) ...

    Abstract The perovskite (BA)
    Language English
    Publishing date 2023-04-12
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2011836-3
    ISSN 1521-3773 ; 1433-7851
    ISSN (online) 1521-3773
    ISSN 1433-7851
    DOI 10.1002/anie.202300957
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  5. Article ; Online: White-Light Emission from Layered Halide Perovskites.

    Smith, Matthew D / Karunadasa, Hemamala I

    Accounts of chemical research

    2018  Volume 51, Issue 3, Page(s) 619–627

    Abstract: With nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To ... ...

    Abstract With nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white. However, combining emitters leads to changes in the emission color over time due to the unequal degradation rates of the emitters and efficiency losses due to overlapping absorption and emission energies of the different components. A single material that emits broadband white light (a continuous emission spanning 400-700 nm) would obviate these problems. In 2014, we described broadband white-light emission upon near-UV excitation from three new layered perovskites. To date, nine white-light-emitting perovskites have been reported by us and others, making this a burgeoning field of study. This Account outlines our work on understanding how a bulk material, with no obvious emissive sites, can emit every color of the visible spectrum. Although the initial discoveries were fortuitous, our understanding of the emission mechanism and identification of structural parameters that correlate with the broad emission have now positioned us to design white-light emitters. Layered hybrid halide perovskites feature anionic layers of corner-sharing metal-halide octahedra partitioned by organic cations. The narrow, room-temperature photoluminescence of lead-halide perovskites has been studied for several decades, and attributed to the radiative recombination of free excitons (excited electron-hole pairs). We proposed that the broad white emission we observed primarily stems from exciton self-trapping. Here, the exciton couples strongly to the lattice, creating transient elastic lattice distortions that can be viewed as "excited-state defects". These deformations stabilize the exciton affording a broad emission with a large Stokes shift. Although material defects very likely contribute to the emission width, our mechanistic studies suggest that the emission mostly arises from the bulk material. Ultrafast spectroscopic measurements support self-trapping, with new, transient, electronic states appearing upon photoexcitation. Importantly, the broad emission appears common to layered Pb-Br and Pb-Cl perovskites, albeit with a strong temperature dependence. Although the emission is attributed to light-induced defects, it still reflects changes in the crystal structure. We find that greater out-of-plane octahedral tilting increases the propensity for the broad emission, enabling synthetic control over the broad emission. Many of these perovskites have color rendering abilities that exceed commercial requirements and mixing halides affords both "warm" and "cold" white light. The most efficient white-light-emitting perovskite has a quantum efficiency of 9%. Improving this value will make these phosphors attractive for solid-state lighting, particularly as large-area coatings that can be deposited inexpensively. The emission mechanism can also be extended to other low-dimensional systems. We hope this Account aids in expanding the phase space of white-light emitters and controlling their exciton dynamics by the synthetic, spectroscopic, theoretical, and engineering communities.
    Language English
    Publishing date 2018-02-20
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 1483291-4
    ISSN 1520-4898 ; 0001-4842
    ISSN (online) 1520-4898
    ISSN 0001-4842
    DOI 10.1021/acs.accounts.7b00433
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Doubling the Stakes: The Promise of Halide Double Perovskites.

    Wolf, Nathan R / Connor, Bridget A / Slavney, Adam H / Karunadasa, Hemamala I

    Angewandte Chemie (International ed. in English)

    2021  Volume 60, Issue 30, Page(s) 16264–16278

    Abstract: When the stakes are doubled in a wager, a player must correctly place two consecutive bets to win, but the payout is larger. Similarly, two B sites in combination dictate the properties of ... ...

    Abstract When the stakes are doubled in a wager, a player must correctly place two consecutive bets to win, but the payout is larger. Similarly, two B sites in combination dictate the properties of A
    MeSH term(s) Alloys/chemistry ; Calcium Compounds/chemistry ; Coordination Complexes/chemistry ; Dimerization ; Ferrocyanides/chemistry ; Molecular Structure ; Oxides/chemistry ; Structure-Activity Relationship ; Thermodynamics ; Titanium/chemistry ; Transition Elements/chemistry
    Chemical Substances Alloys ; Calcium Compounds ; Coordination Complexes ; Ferrocyanides ; Oxides ; Transition Elements ; perovskite (12194-71-7) ; Titanium (D1JT611TNE) ; ferric ferrocyanide (TLE294X33A)
    Language English
    Publishing date 2021-03-26
    Publishing country Germany
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S. ; Review
    ZDB-ID 2011836-3
    ISSN 1521-3773 ; 1433-7851
    ISSN (online) 1521-3773
    ISSN 1433-7851
    DOI 10.1002/anie.202016185
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  7. Article ; Online: Tuning Defects in a Halide Double Perovskite with Pressure.

    Wolf, Nathan R / Jaffe, Adam / Slavney, Adam H / Mao, Wendy L / Leppert, Linn / Karunadasa, Hemamala I

    Journal of the American Chemical Society

    2022  Volume 144, Issue 45, Page(s) 20763–20772

    Abstract: Dopant defects in semiconductors can trap charge carriers or ionize to produce charge carriers─playing a critical role in electronic transport. Halide perovskites are a technologically important semiconductor family with a large pressure response. Yet, ... ...

    Abstract Dopant defects in semiconductors can trap charge carriers or ionize to produce charge carriers─playing a critical role in electronic transport. Halide perovskites are a technologically important semiconductor family with a large pressure response. Yet, to our knowledge, the effect of high pressures on defects in halide perovskites has not been experimentally investigated. Here, we study the structural, optical, and electronic consequences of compressing the small-bandgap double perovskites Cs
    Language English
    Publishing date 2022-11-07
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.2c08607
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  8. Article ; Online: Tuning the Luminescence of Layered Halide Perovskites.

    Smith, Matthew D / Connor, Bridget A / Karunadasa, Hemamala I

    Chemical reviews

    2019  Volume 119, Issue 5, Page(s) 3104–3139

    Abstract: Layered halide perovskites offer a versatile platform for manipulating light through synthetic design. Although most layered perovskites absorb strongly in the ultraviolet (UV) or near-UV region, their emission can range from the UV to the infrared ... ...

    Abstract Layered halide perovskites offer a versatile platform for manipulating light through synthetic design. Although most layered perovskites absorb strongly in the ultraviolet (UV) or near-UV region, their emission can range from the UV to the infrared region of the electromagnetic spectrum. This emission can be very narrow, displaying high color purity, or it can be extremely broad, spanning the entire visible spectrum and providing high color rendition (or accurately reproducing illuminated colors). The origin of the photoluminescence can vary enormously. Strongly correlated electron-hole pairs, permanent lattice defects, transient light-induced defects, and ligand-field transitions in the inorganic layers and molecular chromophores in the organic layers can be involved in the emission mechanism. In this review, we highlight the different types of photoluminescence that may be attained from layered halide perovskites, with an emphasis on how the emission may be systematically tuned through changes to the bulk crystalline lattice: changes in composition, structure, and dimensionality.
    Language English
    Publishing date 2019-01-28
    Publishing country United States
    Document type Journal Article
    ZDB-ID 207949-5
    ISSN 1520-6890 ; 0009-2665
    ISSN (online) 1520-6890
    ISSN 0009-2665
    DOI 10.1021/acs.chemrev.8b00477
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  9. Article ; Online: Single Ensemble Non-exponential Photoluminescent Population Decays from a Broadband White-Light-Emitting Perovskite.

    Thomaz, Joseph E / Lindquist, Kurt P / Karunadasa, Hemamala I / Fayer, Michael D

    Journal of the American Chemical Society

    2020  Volume 142, Issue 39, Page(s) 16622–16631

    Abstract: The mechanism of white-light emission from layered Pb-X (X = Cl or Br) perovskites following UV excitation has generated considerable interest. Prior time-dependent studies indicated that the broadband photoluminescence (PL) from (110) perovskites arises ...

    Abstract The mechanism of white-light emission from layered Pb-X (X = Cl or Br) perovskites following UV excitation has generated considerable interest. Prior time-dependent studies indicated that the broadband photoluminescence (PL) from (110) perovskites arises from a distribution of self-trapped excitonic sites emitting in different regions of the visible spectrum with different decay dynamics. Here, using time-correlated single photon counting to study single crystals, we show that the white-light emission decay from the (110) perovskite (EDBE)PbBr
    Language English
    Publishing date 2020-09-18
    Publishing country United States
    Document type Journal Article ; Research Support, U.S. Gov't, Non-P.H.S. ; Research Support, Non-U.S. Gov't
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.0c05636
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  10. Article: Dimensional reduction of the small-bandgap double perovskite Cs

    Connor, Bridget A / Biega, Raisa-Ioana / Leppert, Linn / Karunadasa, Hemamala I

    Chemical science

    2020  Volume 11, Issue 29, Page(s) 7708–7715

    Abstract: Quantum confinement effects in lower-dimensional derivatives of the ... ...

    Abstract Quantum confinement effects in lower-dimensional derivatives of the ABX
    Language English
    Publishing date 2020-06-05
    Publishing country England
    Document type Journal Article
    ZDB-ID 2559110-1
    ISSN 2041-6539 ; 2041-6520
    ISSN (online) 2041-6539
    ISSN 2041-6520
    DOI 10.1039/d0sc01580f
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