The Technological Innovation System (TIS) is a theoretical approach to the analysis of a new technology's diffusion dynamics. The development and establishment of market-related structures are essential for maturing a TIS and its long-term success, especially at the beginning of sectoral development. In this paper, we focus on market formation in the Turkish solar electricity generation TIS to understand how the market forms. We made an empirical study and benefitted from structural analysis, functional analysis, and process analysis to point out how green transition efforts have started with the market formation process in the Turkish solar energy sector during the first phase of sectoral development. We conducted fifty-seven interviews with key experts in the energy sector in the 2013-2015 period when the sector just started to develop. The structural analysis showed that the most active actors are companies, consultancy organizations, public organizations, and real persons; networks are associations and cooperative organizations, and institutions are general legislation and political developments. The process analysis showed that the constitutive processes are institutionalizing and associating for the formation of market segments, and competing and communicating for the formation of market transactions. The functional analysis pointed out that at the beginning of the TIS development, the market formation was in the nursing phase, but developing very fast.