One-Dimensional Perovskite-like Cu(I)-Halides with Ideal Bandgap Based on Quantum-Well Structure

Low-dimensional halide perovskites with quantum-well structures are promising materials for electronics and optoelectronics because of their excellent optoelectronic properties. This work concerns two novel, lead-free, one-dimensional organic-inorganic hybrid perovskite-like Cu(I) halides, (MV)Cu₂X₄ (MV = methyl viologen; X = Br, I), for optoelectronic applications. Both Cu(I) halides exhibited good stability under ambient conditions. The optical bandgaps of (MV)Cu₂Br₄ and (MV)Cu₂I₄ are 1.4 and 1.5 eV, respectively, which are in the ideal bandgap range for solar cells. (MV)Cu₂Br₄ possessed a characteristic quantum-well structure in which [CuBr₄]³ chains with a nanowire-like structure were rolled up and isolated by tightly packed organic cations. Thanks to quantum confinement in the unique structure, the optical bandgap of (MV)Cu₂Br₄ fell in the ideal bandgap range for solar cells and was superior to that of (MV)Cu₂I₄. The good photoresponse properties of these Cu(I) halides suggest their great potential for application as light-harvesting materials in solar cells.