Broadband Emission in a New Two-Dimensional Cd-Based Hybrid Perovskite

Organic–inorganic hybrid perovskites (OIHP) are developing rapidly as high-performance semiconductors for solid-state solar cells and light emitting devices. Recently, lead-halide two-dimensional (2D) OIHP were found to present bright broadband visible emission, thus, highlighting their potential as single component white-light (WL) emitters. This contribution deals with the preparation of a new Cd-based 2D hybrid perovskite, of the chemical formula (C6H11NH3)2CdBr4 (abbreviated as compound 1), of which structural and optical properties have been studied and analyzed. Room temperature optical absorption (OA) measurements, performed on spin-coated film of compound 1, revealed a sharp excitonic absorption peak at 3.24 eV, and a large exciton binding energy of 377 meV, estimated from low temperature OA spectrum. Upon 325 nm irradiation, compound 1 showed a very broadband WL emission consisting of one peak at 2.94 eV, attributed to exciton confined in the [CdBr4]2– inorganic layers, and a second peak at 2.53 eV resulting from the cyclohexylammonium cations emission. Temperature dependence of PL spectra evidenced anomalous behavior accompanied by singularities around 50 and 150 K in the integrated intensity, the full width at half-maximum and the PL peaks positions. These singularities have been traced back to structural phase transitions, from temperature dependence powder and single crystal X-ray diffraction investigations, from which strong correlations had emerged between the structural distortion of the CdBr6 pseudo-octahedron and the broadening characteristics of the WL emission band. These hitherto unrecognized properties turn this and similar OIHP into perspective candidates for potential applications as WL-emitting diodes.