Dipartimento di Fisica |
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High efficiency white light emission with double perovskites Cs2Na1−xAgxIn1−yBiyCl6
with Bi and Ag Double perovskites can generate warm white
light with very high efficiency, while being constituted by non-toxic earth-abundant
materials, and showing high stability and and reliability. Our study on these
materials, published in Journal of Mat. Chemistry C (Liu,
F. et al., 2022), show how the emission efficiency is correlated to the
presence of small amounts of Ag or Bi, depending on the compound, allowing us
to identify best compositions. The results are supported by simulations with ab initio methods ant ultrafast optical
spectroscopy measurements, that allowed us to link the performances to the
formation of self-trapped excitons (STE) in the material. |
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Direct measurement of radiative decay rate in hybrid perovskites An accurate calibration of the
experimental setup for the measurement of time-resolved photoluminescence
(TRPL) allowed us to directly assess the radiatice decay rate of
photocarriers in hybrid perovskites. The results are showing that in the
analyzed compounds this values is surprising lower with respect to what found
with different indirect techniques, based on the fit of radiative decay
profile with ABC equations. The results published in A. Simbula et al. (2022), pave the way to
new strategies for the optimization of perovskite solar cells. |
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Ultrafast tandem spectroscopy on perovskite thin films We developed a tandem technique in which
time-resolved photoluminescence (TRPL) and transient absorption (TA) are
measured in the very same region of a thin film, allowing us to compare the
result of the two techniques in a region with the same injected carrier
density. By applying it to hybrid perovskite thin films, both 3D and 2D, we
were able to establish a link between the radiative and non-radiative carrier
lifetimes, getting important insights on the carrier
dynamics: the ratio between radiative and non-radiative process is not
compatible with excitons as majority carriers. From a deep analysis of
experimental evidences, reported in A. Simbula et al.
(2021), a behaviour compatible with presence
of minoritary bright excitons emerged,
whose lifetime is governed by chemical equilibrium with a majority of
dark polarons. |
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Lead-free double perovskites for
high-efficiency light sources Double perovskites are made from two different species
of cations and their emission properties are strongly depending on doping
with silver and bismuth: their absorption and photoluminescence quantum yield
can be controlled by a precise tuning of the doping amount and on the ratio
of the cations (F. Liu et al. (2020) |
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Tesi disponibili Hybrid perovskite solar cells Femtosecond spectroscopy on
thin films Nanomaterials synthesis Exploratory synthesis of
halide perovskites Characterization of materials
for LED sources |
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