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  • Author(s):
    Junsang Cho, Jeffrey T. DuBose, Prashant Kamat
    Abstract:

    Lead-free double perovskites such as Cs2AgBiBr6 are gaining attention because of their environmental friendliness compared to the lead halide perovskites. In order to establish their photoactivity, we have probed the excited-state behavior of Cs2AgBiBr6 nanocrystals and charge injection from their excited state into different metal oxides (TiO2, ZnO). The electron-transfer rate constants determined from ultrafast transient absorption spectroscopy were in the range of 1.2−5.2 × 1010 s−1. Under…

    Date Published:
    2019-12
    Record Visibility:
    Public
  • Author(s):
    Gergely Samu, Adam Balog, Filippo De Angelis, Daniele Meggiolaro, Prashant Kamat, Csaba Janáky
    Abstract:

    Abstract Halide ion mobility in metal halide perovskites remains an intriguing phenomenon, influencing their optical and photovoltaic properties. Selective injection of holes through electrochemical anodic bias has allowed us to probe the effect of hole trapping at iodide (0.9 V) and bromide (1.15 V) in mixed halide perovskite (CH3NH3PbBr1.5I1.5) films. Upon trapping holes at the iodide site, the iodide gradually gets expelled from the mixed halide film (as iodine and/or triiodide ion), leavi…

    Date Published:
    2019-06
    Record Visibility:
    Public
  • Author(s):
    Ádám Balog, Gergely Samu, Prashant Kamat, Casba Janáky
    Abstract:

    Detailed mechanistic understanding of the optoelectronic features is a key factor in designing efficient and stable photoelectrodes. In situ spectroelectrochemical methods were employed to scrutinize the effect of trap states on the optical and electronic properties of CuI photoelectrodes and to assess their stability against (photo)electrochemical corrosion. The excitonic band in the absorption spectrum and the Raman spectral features were directly influenced by the applied bias potential. T…

    Date Published:
    2019-01
    Record Visibility:
    Public
  • Author(s):
    Tor Elmelund, Rebecca Scheidt, Brian Seger, Prashant Kamat
    Abstract:

    MAPbBr3 and MAPbI3 films cast onto glass slides and physically paired together undergo halide exchange to form mixed halide films. The change in halide composition in these two ∼130 nm thick films occurs concurrently with Br− diffusing toward the MAPbI3 film and I− diffusing toward the MAPbBr3 film. The diffusion of these halide species, which is tracked through changes in the absorption, offers a direct measurement of thermally activated halide diffusion in perovskite films. The increase in …

    Date Published:
    2019-06
    Record Visibility:
    Public
  • Author(s):
    Rebecca Scheidt, Corey Atwell, Prashant Kamat
    Abstract:

    The control of grain size and surface properties is an important parameter in controlling the optoelectronic and photovoltaic properties of metal halide perovskites. When CsPbBr 3 nanocrystal (∼10 nm in diameter) films were annealed at 100−125 °C, they grow in size to produce ∼400 nm diameter crystallites while transforming into bulk perovskite films. Characteristic changes in the optical properties were noted when such transformation occurred from nanocrystals into bulk. By tracking absorban…

    Date Published:
    2019-06
    Record Visibility:
    Public