Fotonica e Optoelettronica Dipartimento di Fisica
	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.
	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.
	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.
	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)).
	Tesi disponibili Hybrid perovskite solar cells Femtosecond spectroscopy on thin films Nanomaterials synthesis Exploratory synthesis of halide perovskites Characterization of materials for LED sources