Characterization and optimization of broad absorbing materials for efficient solar energy harvesting

Abstract

Energy plays a key role in the prosperity and development of human society. Over the course of millions of years, fossil fuels, including coal, oil and natural gas, have been used as primary source of energy. Fossil fuel reserves are depleting with each passing day hence an alternative low cost, abundant and environmental friendly source of energy is required. Solar radiation is an unlimited form of clean and renewable energy. Its low cost and efficient harvesting can endlessly fuel our civilization. Dye-sensitized solar cells have been identified as the next-generation solar cells and continue to represent an important area of photovoltaic research because of its many advantages such as low cost, ease of fabrication, transparency, different colors, and clean energy source. In the research undertaken in this work, performance of DSSCs using benzothiadiazole based dyes was compared, the potential of a broad absorbing organic dye as an alternative to a standard metallic dye as a sensitizer was studied, the effect of different layers on the device performance enhancement was examined, a step by step temperature increase method was employed to enhance the device performance, and DSSC performance was investigated employing a highly ordered one-dimensional zinc oxide (ZnO) nanorods based photoanode. To provide insight into the efficient solar energy harvesting and charge transport mechanisms, the techniques of UV-Visible spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), time dependent density functional theory (TDDFT) based computational study, current-voltage measurements, transient photovoltage measurements, transient photocurrent measurements and impedence spectroscopy were performed.