Solar energy is our most abundant natural resource: the energy from sunlight that strikes the Earth in one hour is more than the energy consumed globally in a year. This makes photovoltaics, which convert solar energy into electrical energy, a critical technology to pursue. 95% of the photovoltaic market is dominated by silicon; its high efficiency, stability, and plummeting manufacturing costs made it the clear choice for commercialization. However, silicon solar cells are thick, heavy, opaque, and rigid, limiting potential applications. They are energy- and resource-intensive to produce, and their manufacturing process uses and produces several toxic substances. “Next-generation” photovoltaic technologies have tried to compete with silicon, boasting improvements in efficiency, stability, toxicity, cost, weight, and benefits such as semi-transparency or flexibility. Thus far, none of these technologies have surpassed silicon as each has encountered unique roadblocks. I worked to identify and overcome these roadblocks for two promising next-generation photovoltaic technologies: nanoparticle organic photovoltaics (NP-OPVs) and hybrid organic-inorganic perovskites (HOIPs). Organic photovoltaics (OPVs) are remarkable for their tunable properties, cheaper synthesis, and thin, flexible, lightweight, semi-transparent devices, opening up applications unavailable to silicon cells. However, after decades of development, OPVs lag far behind silicon in efficiency. NP-OPVs are a subset of OPVs which use organic nanoparticle building blocks for eco-friendly fabrication out of water and greater control over material assembly. Currently, NP-OPVs lag even farther behind their OPV counterparts in efficiency. I investigated device characteristics of NP-OPVs to help close the efficiency gap with OPVs and identified a unique application – indoor power generation – for which OPVs and NP-OPVs are uniquely suited. HOIP photovoltaics emerged in the last decade and skyrocketed up to efficiencies competitive with silicon. Like OPVs, they have tunable properties, cheaper synthesis, and can be thin, lightweight, flexible, and semi-transparent. Stability is the major roadblock to HOIP commercialization; these devices break down under light, heat, humidity, and applied bias. I built a comprehensive map of how electronic and ionic charge carriers move in response to light, bias, and degradation, and synthesized HOIP derivatives which showed substantial increases in stability under light while maintaining their desirable properties.