Sustainable energy harvesting, such as solar energy, depends increasingly on nanotechnology components. This article will look briefly at the principles of photovoltaic units and elucidate the toxicological aspects of its principal components, namely fullerenes and carbon nanotubes. Through this approach, we address the rebound effect related to health adverse and environmental aspects which is a key issue to be solved when innovating in energy harvesting. The understanding of sustainability in this context is that the technology provides lasting improvement by bringing environmental compatibility along with technological agility, providing major reductions in both material and energy resource use and avoid negative impacts on our environment and health. With the rebound effect we understand the unintended emergence of negative environmental impacts resulting from intentions of improving environmental issues. Sustainable energy-harvesting, such as solar energy, depends increasingly on nanotechnology components. This article provides a brief overview of photovoltaic units and the toxicological aspects of their principal components, namely fullerenes and carbon nanotubes. It will then address the adverse, rebound effects on human health and the environment, the next key issue to be resolved within energy-harvesting innovation. Sustainability in this context, refers to the role of technology in providing lasting improvement through environmental compatibility combined with technological agility that enables major reductions in both material and energy resource use and minimizes negative impacts on health and the environment. The rebound effect, refers to the unintended emergence of negative environmental impacts as a result of remedial actions designed initially to improve the environment. These will be discussed in context with the two major classes of nanomaterials in consumer electronics: fullerenes and carbon nanotubes, which carry a series of properties that make them classifiable as hazardous materials.