Excitation‐Wavelength‐Dependent Emission of Congruently Melting Iodocuprate Hybrid Materials

Abstract In the context of the emergence of metal halide perovskites for optoelectronic materials, the lead‐free and earth‐abundant copper(I)‐based halide hybrids are of high interest. Here, we report on two iodocuprate hybrids (HO 2 C(CH 2 ) n ‐1 NH 3 )CuI 2 ( n = 3, 4) exhibiting excitation‐wavelength‐dependent emission. The thermodynamically stable n = 4 compound (2D‐C4) is based on a rare 2D iodocuprate network, while a more common 1D network of edge‐sharing tetrahedra is found both in the n = 3 compound (1D‐C3) and in the metastable n = 4 (1D‐C4) hybrid. Depending on the excitation wavelength, 2D‐C4 and 1D‐C3 hybrids exhibit yellow emission, red emission, or white light emission—resulting from the emission of both components,—while 1D‐C4 does not emit in the red region. The description of the electronic structure based on density functional theory (DFT) indicates two different origins for the emissions of 2D‐C4 and 1D‐C3, in particular from iodide vacancies (red emission), which involve mid‐gap states. The emission of 2D‐C4 can also be modulated from red to yellow depending on applied pressure. 2D‐C4 also has an exceptionally low congruent melting temperature of 110 °C, allowing the solvent‐free preparation of thin films. Finally, phosphor‐converted‐LED based on 2D‐C4 have been prepared, showing that either pink or nearly white emission is produced.