In this thesis, I study the barriers to the diffusion of clean technologies, whether policies can overcome them, and how they do so. By looking at the diffusion of clean technologies across both households and firms, and with a special focus on developing countries, I identify specific challenges to the diffusion of three types of clean technologies across agents, and whether implementation of policies in these specific contexts have been effective in surmounting them. In the first chapter, I study the determinants of policy choice and their subsequent effectiveness in the diffusion of compact fluorescent lamps (CFL) through a sample of low and middle-income countries. In particular, I examine the role of information provision, subsidies, and banning the sale of the incumbent technology in facilitating CFL diffusion, and also study the determinants of policy choice in these countries. The second chapter is a study on the nature of spatial disparities that exist in the adoption of liquefied petroleum gas (LPG) amongst Indian households, and the role of spillovers and social networks in facilitating the adoption of LPG through information flows. In the third chapter, I study innovation in clean technologies by firms along the value chain to the automotive industry, in response to environmental regulation imposed on automotive companies globally. All the errors in this thesis are mine.