Zero-Dimensional Methylammonium Bismuth Iodide-Based Lead-Free Perovskite Capacitor.

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 (CH3NH3)3Bi2I9, a lead-free, zero-dimensional hybrid perovskite material. A maximum areal capacitance of 5.5 mF/cm2 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.