Despite the enormous potentials of Iran to generate electricity from photovoltaic solar systems, diffusion of these systems is very slow. The present study, which was performed during the period of 2016-2018 by combining multi-level approaches and technological innovation system, seeks to identify and investigate the barriers that Iran's fossil-fuel socio-technical regime has created in its historical and cultural context caused non-transition to photovoltaic solar systems. For this purpose, firstly, after reviewing the literature, interviewing the experts and thematic analysis, transition barriers with emphasis on the regime were identified and then Fuzzy Delphi technique was used to test the results. Eventually, 10 obstacles were categorized into four economic, institutional, political and technical categories, including market control by the ruling regime, the use of discursive strategies, regulation and standards in stabilizing the ruling regime, massive investment in oil and gas distribution and extraction. In the second phase, interviews with experts and the use of the Strategic Options Development and Analysis (SODA) method indicated that these barriers had the greatest impact on the functions of resource allocation, legitimization, and system orientation. Finally, some mechanisms have been proposed to overcome these obstacles.