Innovation and diffusion of clean energy technology is essential for moving toward a green economy in a carbon-constrained world. While the developed world is trying to transition to a more carbon-neutral energy mix, developing countries are struggling to secure sufficient energy to meet basic human needs. The objective of this research project was to provide an in-depth investigation of the determinants of the diffusion of clean energy technologies to developing countries. The project relied on conceptual methods from both the economic (e.g international technology diffusion and trade literature) and political science literature (e.g studies on energy governance, regime complexity, effectiveness and social learning) and contributed to new empirical insights. Although the research project investigated different barriers to clean energy diffusion and different kinds of technologies (efficient lightings, clean cookstoves, renewable energy among which geothermal in particular), the collective contribution of the project highlights the critical importance of domestic policies and policy learning enabled by clean energy governance, openness to trade and imports of new technologies, and social diffusion and peer-group effects to diffuse information among consumers.