Considering the role of renewable energy sources in the sustainable development process of countries and the significance of economic and political stability in financing renewable energy projects, this research utilizes the Panel Smooth Transition Regression (PSTR) model in various separate models to investigate the impact of systematic risk (including political, economic, and financial risks) on the relationship between financial development (stock market development and banking sector development) and the development of renewable energy technologies (RET) in oil-producing countries (including developing and developed oil-producing countries) during the period from 2000 to 2021. Using nonlinear behavior detection tests, the existence of a nonlinear relationship between financial development and the development of renewable energy technologies was confirmed. The systematic risk variable was chosen as an appropriate transition variable, and a nonlinear panel regression model with a two-regime logistic transition function with a one-time transition was considered as the proposed pattern for this relationship. The overall results of the model estimations indicate that the relationship between financial development and the development of renewable energy technologies varies depending on the level of systematic risk in countries. An increase in the numerical index of risk from its threshold value and entry into the second regime, indicating a reduction in risk levels in countries, enhances the positive impact of financial development on the development of renewable energy technologies. The findings also suggest that in the first regime and at higher risk levels (before the threshold), the banking sector, compared to the capital market, has a greater impact on the development of RET in oil-producing countries. However, in the second regime where the risk level is lower (after the threshold), both the banking sector and the capital market have a positive impact on the development of RET. Additionally, the results show that different indicators of financial development and risk have varying effects on the development of RET in developing and developed oil-producing countries.
