Optical characterization of CsCu2I3 and Cs3Cu2I5 metal halide perovskites

Abstract

Ternary copper halide compounds, where copper presents oxidation state +1 (Cu+), have been of great interest because of their optoelectronic properties. In particular, cesium copper halide nanostructures with composition either CsCu2I3 or Cs3Cu2I5 are materials with excellent emission properties within the visible range, driven by self-trap exciton mechanism. In this work we study the optical properties of two copper based halide perovskites, CsCu2I3 and Cs3Cu2I5, first at room temperature and later with dependence on temperature. We found that the excitation of the PLE is occurring in the UV region, in agreement with the absorption edge. As a function of the temperature, the band gap decreases with the temperature for both composition, however the emission behaviour exhibits an apparent anomalous behaviour with temperature. The results are discussed in terms of the excitation energy and the bandgap dependence with temperature