INTEGRATED PHOTORECHARGEABLE PEROVSKITE BASED SUPERCAPACITOR FOR ENERGY HARVESTING AND STORAGE APPLICATIONS

Abstract

This Master's thesis aims to investigate lead free halide perovskites as innovative materials for energy storage devices. The goal is to develop smart perovskite electrodes with high efficiency and energy density for use in photo-rechargeable energy storage devices. The research considers the development of lead-free devices and addresses the challenge of poor interaction between binders and active materials. Lead-based halide perovskites have been widely used as efficient energy materials due to their superior optoelectronic properties and mixed electronic ionic conductivity. However, lead toxicity has been one of the key challenges for commercialization. Recently Cs2AgBiBr6, a lead-free double perovskite, has garnered significant interest due to its exceptional stability, nontoxic nature, and promising optoelectronic properties. But because of the low electronic and ionic conductivity of bismuth based double perovskites, there is a challenge for their use in energy storage applications. To resolve this issue, we have incorporated carbon black and a conducting polymer poly(2,3 dihydrothieno-1,4-dioxin)-poly (styrene sulfonate) (PEDOT: PSS) as electronic and ionic conductivity agents respectively into Cs2AgBiBr6 porous electrode. This ternary composite exhibits over 40% enhancement in specific capacitance as well as specific energy density compared to a binary composite of carbon black with a perovskite electrode. There is no significant change in the power density. However, only PEDOT: PSS as charge transporting materials in perovskite matrix results in lower energy density and power density despite lower charge transfer resistance (Rct) at the electrode/electrolyte interface and higher dc ionic conductivity compared to perovskite/carbon composite electrodes. From the electrochemical impedance spectroscopy analysis, it is evident that balanced ionic and electronic conductivity is necessary to achieve optimal performance in lead-free perovskite-based supercapacitors. We have also fabricated a solid-state symmetric supercapacitor using a quasi-solid-state gel electrolyte which was then integrated with solar cell. The ultimate aim is to contribute to the development of sustainable energy storage solutions.