Organic solar cells: Study of combined effects of active layer nanostructure and electron and hole transport layers

An organic solar cell based on poly (3-hexathiophine-2,5-diyl) and [6,6]-phenyl C₆₁ butyric acid methyl ester has been subjected to all layers treatment and was investigated for combined effects of the these layers on device performance. These treatment included optimization of active layer morphology and thickness and improving the structure of the hole and electron transport layers, as well as subjecting the full device to optimum post deposition thermal treatment. Such a device has shown an increase in the optical absorption intensity in the near infrared region compared to the reference device, which is thought to be advantageous for producing high current density. The increase in the current density has also been correlated with light trapping within the active layer and the possibility of the occurrence of total internal reflection, which was explained using total internal reflection spectroscopic ellipsometry measurements. The current density-voltage characteristics have been measured in dark and under illumination. Power conversion efficiency as high as 7% has been achieved correlated with a fill factor of 71%. - Highlights: • Optimisation of all layers treatment of organic solar cells • Improved charge collection due modification of charge transport layers • Improved short circuit current density is ascribed to light trapping. • Total internal reflection may explain efficient light harvesting efficiency. • Power conversion efficiency as high as 7% has been achieved.