Low-Temperature study of Optical Properties from CsCu2I3 NCs
Joshua Diago a b, Sergi Garcia a b, Sergi Hernández a b, Sergio Gonzaález-Torres a b, Gayathri Mathiazhagan a b, Giovanni Vescio a b, Paolo Pellegrino a b, Jordi Ibáñez-Insa c, Blas Garrido a b, Albert Cirera a b
a MIND, Department of Electronics and Biomedical Engineering, Universitat de Barcelona, Martí i Franquès 1, E-08028, Barcelona, Spain
b Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Av. Joan XXIII S/N, E-08028, Barcelona, Spain.
c Geosciences Barcelona (GEO3BCN), Spanish Council for Scientific Research (CSIC), Lluís Solé i Sabarís s/n, 08028 Barcelona, Spain.
Proceedings of Sustainable Metal-halide perovskites for photovoltaics, optoelectronics and photonics (Sus-MHP)
València, Spain, 2022 December 12th - 13th
Organizers: Teresa S. Ripolles and Hui-Seon Kim
Poster, Joshua Diago, 031
Publication date: 15th November 2022

Cesium Copper Iodide compounds exhibit great interest due to their high stability and excellent optoelectronic properties. In particularly, the one-dimensional phase with stoichiometric ratio CsCu2I3 presents emission based on self-trapped exciton (STE) at ~2.2 eV, with a reported photoluminescence (PL) quantum yield (PLQY) as high as ~20%. This material shows large Stokes shift, with band gap energies around 3.8 eV, long lifetimes (~ 149 ns), and high exciton biding energy (around 315 meV at room temperature).

In this work, we have synthesized CsCu2I3 nanocrystals by using a simple one-pot method at 80 °C, by dissolving CsI and CuI, in a molar ratio of 1:2, in N,N-Dimethylformamide. Subsequently the solution was deposited by Drop-Casting and annealed at 100 °C for 45 minutes. The crystalline structure and chemical composition have been determined by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The results confirm the structure is orthorhombic and the stoichiometry of this compound is 1:2:3, which matches with the atomic ratio of CsCu2I3. Temperature dependence PL and transmittance measurements have been performed for determining the band gap and emission energies, from 10 K up to room temperature. Considering the temperature evolution of the PL integrated intensity, PL peak-energy, and bandgap energy we were able to estimate the energy binding energy and self-trapped exciton level energy, obtaining values of 120 meV and ~1.45 eV, respectively.

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