Low-dimensional perovskites are an emerging class of materials with high stability and excellent optoelectronic properties. Herein, we introduce a novel, lead-free, zero-dimensional perovskite-like material, (1,3-propanediammonium) 2 Bi 2 I 10 •2H 2 O, for optoelectronic applications. This material exhibited good moisture and thermal stability under ambient conditions. Single-crystal X-ray diffraction analysis revealed a quantum-well structure having the inorganic Bi 2 I 10 4− clusters periodically arranged in the crystallographic "c" axis separated by a distance of 5.36 Å, sandwiched by independent layers of organic cations. The density functional theory calculations showed that the oxygen in water molecules has a significant contribution to the band edges of the material. The photodetector device fabricated using this material showed an efficient charge separation at low voltage (1 V) due to the good electronic conduction between the Bi 2 I 10 4− dimer units.H ybrid perovskites have emerged as a unique semiconductor material for various optoelectronic device applications during the past few years. 1−3 Excellent properties such as long charge carrier diffusion length, low exciton binding energy, facile band gap tunability, and low-temperature solution processability made this material highly useful in these devices. 4−7 Nevertheless, poor stability under ambient conditions and toxicity of lead hampers their commercial usage. 8,9 Reports suggest that lower dimensional perovskites exhibit moisture tolerance to a great extent. 10−13 In order to address the toxicity issue, less toxic metal ions, such as Sn 2+ , Bi 3+ , Sb 3+ , and so forth, having ns 2 electrons similar to Pb 2+ were introduced into the perovskite structure. 14−16 Among them, tin-based materials are highly unstable due to the facile oxidation of the Sn 2+ to Sn 4+ state. 17 On the other hand, bismuth-and antimony-based zero-dimensional perovskites exhibited excellent moisture stability due to their rigid M 2 X 9 3−

Symmetrical electrochemical capacitors are attracting immense attention because of their fast charging–discharging ability, high energy density, and low cost of production. The current research in this area is mainly focused on exploring novel low-cost electrode materials with higher energy and power densities. In the present work, we fabricated an electrochemical double-layer capacitor using methylammonium bismuth iodide (CH 3 NH 3 ) 3 Bi 2 I 9 , a lead-free, zero-dimensional hybrid perovskite material. A maximum areal capacitance of 5.5 mF/cm 2 was obtained, and the device retained 84.8% of its initial maximum capacitance even after 10 000 charge–discharge cycles. Impedance spectroscopy measurements revealed that the active layer provides a high surface area for the electrolyte to access. As a result, the charge transport resistance is reasonably low, which is advantageous for delivering excellent performance.

CH3NH3PbBr3based luminescent perovskite nanoparticles have been used for the selective detection of an explosive, 2,4,6-trinitrophenol (picric acid) with high sensitivity in solution and vapour state.