Photovoltaic (PV) technologies are a promising approach to achieve clean, renewable energy production on a global scale. However, the widespread implementation of this technology is limited due to the intricate challenges associated with its complex electrochemical processes. One such challenge is the formation of long-lived charge-separated states (CSSs), a process that directly influences device efficiencies. Viable strategies for increasing CSS lifetimes involve the inhibition of parasitic back-electron transfer pathways. In liquid-junction PVs, electronic recombination is prevented by utilizing redox electrolytes that promote directional electron transfer at the electrode/electrolyte interface, where forward electron transfer (i.e. to the electrode) is favored and the corresponding electronic recombination reaction is impeded. To meet this criterion, researchers seek to employ redox electrolytes that undergo a spin-exchange reaction induced by electron transfer. This event, known as charge transfer-induced spin crossover (CTISC), significantly increases the reorganization energy associated with electronic recombination, producing long-lived CSSs and elevated device efficiency. This dissertation describes a suite of manganese-based redox mediators that exhibit CTISC across a tunable range (1.5 V) of formal potentials (E1/2). These complexes are utilized as redox electrolytes in liquid-junction PVs and result in a two-fold enhancement in the device efficiency relative to other CTISC redox species. Photosensitizer regeneration rates are monitored using transient absorption spectroscopy (TAS) to discern the optimal E1/2 values in this class of complexes while density functional theory is employed to calculate the reorganization energy of each species. By implementing these promising electrolytes into PV devices, scientists and engineers are armed with new tools to increase the accessibility and efficiency of next-generation PVs, thereby transforming past promises into progress. / Doctor of Philosophy / To realize next-generation renewable fuels, scientists must understand how electron transfer at an interface is controlled. This dissertation highlights one method of forming a chemically useful and long-lived charge separated state. The formation of this charge separated state is achieved through an electronic reorganization that occurs at a metal center after electron transfer. Chapters 2, 3, and 4 investigate the synthesis and characterization of new metal species that possess this electronic reorganization process and provide an advanced understanding of how this process facilitates the formation of long-lived charge separated states. This work is intended to motivate new schools of thought that aid the design of next-generation catalytic materials for light-driven chemical reactions.