Perovskite solar cells (PSCs) have risen to the forefront of versatile thin-film technologies with power conversion efficiencies rivaling traditional silicon and the potential to be fabricated at a fraction of the cost. However, one crucial drawback to PSCs is their instability to illumination, which is likely due in part to mobile ions during operation. It is difficult to predict the influences of ion dynamics in devices, and the exact nature and impact of these ions remain elusive. In this dissertation work, I have set out to unravel the complex interplay between ions and device operation in PSCs. Through the development of novel techniques and the deployment of detailed analysis, we have been able to contribute key insight into essential questions surrounding ion dynamics in PSCs, including insight into the chemical nature of mobile ion(s), the operational influences of ionic accumulation in devices, the influence of ions during device fabrication, and strategies to stabilize PSCs through the impedance of ion transport pathways. Ultimately, this work contributes to a more comprehensive understanding of the role of ions in PSCs, which has allowed us to make informed decisions aimed to develop stabilized materials for the next generation of solar cells.