Document Type

Honors Project

First Advisor

Ian McNeil

Degree Award Date

Spring 5-3-2025

Keywords

Solar Cells, Potential, Chemical Additives, Electron Diffusion

Disciplines

Biochemistry, Biophysics, and Structural Biology | Life Sciences

Abstract

Solar energy plays a critical role in reducing greenhouse gas emissions and mitigating climate change by converting sunlight into usable electricity and heat. While silicon-based solar cells remain the dominant technology, dye-sensitized solar cells (DSSCs) offer a cost-effective alternative by using semiconductors and light-absorbing materials. Although DSSCs have the potential to provide cost-effective solutions, their efficiency tends to be lower than that of silicon solar cells. They face significant challenges such as back electron transfer. This phenomenon occurs when injected electrons recombine with redox mediators or oxidized dyes, reducing the overall efficiency of the cell. To address this, we explored the effect of two additives – lithium ions (Li+) and 4-tert-butyl-pyridine (tBp) – on electron diffusion within unsensitized solar cells (USSCs). Lithium ions are thought to lower the energetic levels of trap states – areas within the material’s crystal structure that can capture and hold electrons – making it easier for electrons to be captured. Conversely, tBp can increase the energetic levels of the trap states, making it more difficult. We hypothesized that lowering energetic trap states can retain electrons for longer periods of time by preventing electron diffusion to higher energy neighboring acceptor states. Furthermore, to analyze these effects, chronopotentiometry was used to track the flow of electrons through the system. Experiments were conducted using a potentiostat, and the resulting data was analyzed in RStudio to observe the time-dependent voltage decay curves. This study aims to examine the influence of lithium ions and tBp on electron lifetimes and how these factors impact the overall efficiency of USSCs. Additionally, the difference in performance between TiO2 and ZrO2 was examined as well as exploring differences in the length of applied bias.

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