MIXED-HALIDE PEROVSKITE BASED PHOTO-RECHARGEABLE SUPERCAPACITOR

Abstract

The central concept of this Master's thesis is to development of innovative materials for energy storage devices. We have studied the basic properties of mixed halide perovskites (single crystals, polycrystalline, nanomaterial, microns) for energy storage applications. In the last few years, hybris perovskites have gained much attention and are universally used in optoelectronics. Perovskites are extensively used in solar cells, FETs, LEDs, and sensors due to their excellent optoelectronic properties, mainly due to the mixed ionic-electronic conductivity. Due to excellent ion diffusion properties, these materials appear as a strong candidate for both energy conversion and energy storage within the same materials in a single device. However, due to a lack of fundamental knowledge of charge storage mechanisms, the use of perovskites in energy storage is limited. The development of smart perovskite materials for electrodes with high efficiency and high energy density has become significant. By optimizing perovskite's ionic and electronic properties, we can use it in smart off-grid energy devices. The mixed ionic-electronic conductivity of perovskites allows us to operate in photo rechargeable energy storage devices. Towards the energy storage applications, many novel materials have been discovered and used in energy storage devices. Still, due to poor interaction and interface of binder and active material, the device performance is limited, and the overall efficiency of the device is decreased. In this thesis, we proposed binder-free photo-supercapacitor electrodes fabricated with different methods to study the electrochemical properties and cell performance of the energy storage devices. The fabrication of active materials plays an important role in device performance. In this study, we synthesize two types of electrodes. Electrode_1 is synthesis by mixed halide perovskite (𝐶𝐻3𝑁𝐻3𝑃𝑏𝐵𝑟2𝐼) single crystal powder, while Electrode_2 is synthesis by mixing two different perovskite single crystals (𝐶𝐻3𝑁𝐻3𝑃𝑏𝐵𝑟3 + 𝐶𝐻3𝑁𝐻3𝑃𝑏𝐼3, 2:1 molar ratio). The maximum specific capacitance @5 mV/s scan rate for electrode_1 is increased from 26.85 F/g to 28.41 F/g, and for electrode_2, the specific capacitance is decreased from 38.7 F/g to 33.1 F/g when white light is illuminated. Here we observed that the electrode_1 is showing photo capacitance enhancement, while electrode_2 is showing photo-capacitance diminution. The different synthesizing methods play an important role in the photo-capacitance performance of the cell. The random mixtures of electrode materials can result in poor separation and transportation of photogenerated charges and limit the overall photo charge conversion efficiency. The physically mixing of the two dissimilar materials with different energy band structures cause the energy bands to mismatch, this mismatch of bands works as a barrier for charge carriers and photogenerated charges trapped between these mismatched bands.