The industrial sector now depends heavily on cleantech because it unites technological progress with goals to boost operational performance and decrease reliance on conventional resources while creating fresh development prospects. The field delivers environmental advantages while creating industrial transformations that create employment opportunities and strengthen business sustainability. Research efforts need identification of sustaining factors for cleantech firm development and success measurement to understand which nations and industries excel at turning research into tangible outcomes. This thesis focuses on the role of research and development, with particular emphasis on Business Enterprise Expenditure on R&D (BERD), as a driver of firm performance. The analysis takes a comparative perspective across five European economies – Italy, France, Germany, Denmark and the Netherlands – highlighting how differences in spending levels, financing structures and sectoral priorities influence outcomes such as sales growth and employment creation.