However, poor mechanical properties of the materials and hightemperature thermal treatments during the production of solar cells made these approaches unviable [12]. Subsequent experimental results
reported a 9.5% increase in efficiency by introducing Eu(III)-doped silica layers formed by sol-gel processes and placed on top of the Si-based solar cells [8], and a 5% increase using KMgF3:Sm obtained by the vertical Bridgman method [13]. Though, these time and energy consuming
processes are hardly transferred to the industry.