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 (Eg-R = 2.016 eV, Eg-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.