Two-dimensional semiconducting Cu(i)/Sb(iii) bimetallic hybrid iodides with a double perovskite structure and photocurrent response

Stable lead-free hybrid halide double perovskites have sparked widespread interest as a new kind of photoelectric material. Herein, for the first time, we successfully incorporated copper(i) and antimony(iii) into two two-dimensional (2D) hybrid bimetallic double perovskite iodides, namely (NH₃C₆H₁₁)₄CuSbI₈·H₂O (CuSbI-1) and (NH₃C₆H₁₀NH₃)₂CuSbI₈·0.5H₂O (CuSbI-2), using cyclohexylamine and 1,4-cyclohexanediamine as organic components. The band gaps for CuSbI-1 and CuSbI-2 were determined to be 2.22(2) eV and 2.21(2) eV, respectively. Furthermore, these two layered perovskites were readily dissolved in an organic solvent (1 mL DMF can dissolve 1 g sample for each compound) and could form smooth, pinhole-free, and uniform thin films through a facile spin-coating method. Photocurrent experiments with xenon lamp irradiation revealed the obvious photoelectric responses for both 2D double perovskites. The ratio of the photocurrent to the dark current (I_light/I_dark) for CuSbI-1 and CuSbI-2 is about 23 and 10, respectively, further suggesting their potential to be applied as light harvesters or light detectors. More importantly, these 2D double perovskite iodides show high moisture and thermal stabilities, indicating their potential for optoelectronic applications.