1D Chiral Enantiomer Lead-Free Perovskites Induced Chiralopical Activity and Photoelectric Response

Chirality is a fascinating geometrical concept with widespread applications in biology, chemistry, and materials. Incorporating chirality into hybrid perovskite materials can induce novel physical properties (chiral optical activity, nonlinear optics, etc.). Hybrid lead-free or lead-substituted perovskite materials, as representatives of perovskites, have been widely used in fields such as photovoltaics, sensors, catalysis, and detectors. However, the successful introduction of chirality into hybrid lead-free perovskites, which can enable their potential applications in areas such as circularly polarized light photodetectors, memories, and spin transistors, remains a challenging research topic. Here, we synthesized two new chiral lead-free perovskites, [(R)-2-methylpiperazine]­[BiI₅] and [(S)-2-methylpiperazine]­[BiI₅]. The material possesses a perovskite structure with a one-dimensional (1D) arrangement, denoted as ABX₅. This structure is composed of chiral cations, specifically methylpiperazine, and endless chains of [BiI₃] along the a-axis. These chains are assembled from distorted coplanar [BiI₅]^2– octahedra. The testing results revealed that (R)-1 and (S)-1 have narrow band gaps (E_g-R = 2.016 eV, E_g-S = 1.964 eV), high photoelectric response, and long carrier lifetime [R = 4.94 μs (τ), S = 7.85 μs (τ)]. It is worth noting that 1D chiral lead-free perovskites (R)-1 and (S)-1, which are synthesized in this study with narrow band gaps, high photoelectric response, and long carrier lifetime, have the potential to serve as alternative materials for the perovskite layer in future iterations of lead-free perovskite solar cells. Moreover, this research will inspire the preparation of multifunctional, lead-free perovskites.