Two-dimensional semiconducting Cs(i)/Bi(iii) bimetallic iodide hybrids for light detection

Abstract

Lead-based semiconducting organic–inorganic halides such as CH₃NH₃PbI₃ are promising materials for optoelectronic applications. However, the toxicity of lead and the instability of these materials could raise environmental issues if they are applied on a large scale. Herein, two new 2D lead-free bimetallic iodide-based hybrid compounds are presented, namely (C₁₂H₃₀N₄)Cs₃BiI₈ (CsBiI-1) and (C₁₄H₃₅N₄)CsBiI₇ (CsBiI-2), using different amines: C₆H₁₄N₂ = cyclohexane-1,4-diamine (CDA) and C₇H₁₆N₂ = 2-piperidinoethylamine (PDA). These two compounds show optical band gaps of 2.18 eV and 2.39 eV for CsBiI-1 and CsBiI-2, respectively. Both materials yield high surface coverage films from spin-coating. Moreover, CsBiI-1 and CsBiI-2 are stable under moisture and present photocurrent responses. Thus, these materials have the potential for use in light detection.