Effect of thermal annealing on P3HT:PCBM bulk-heterojunction organic solar cells: A critical review

The main focus of this review article is to introduce the reader to the advantage and limitation of organic solar cells and to understand how the thermal annealing process could improve performance of organic solar cells. The article explores the operation principles of organic photovoltaic (OPV) device and reviews the effects of thermal annealing on bulk-heterojunction organic solar cells based on a thin film blend of poly (3-hexylthiophene-2,5 diyl) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). It focuses on changes in the physical film properties, the electronic performance of devices, as well as the link between film structure and electronic performance during a thermal annealing process. Analysis of film and electrical characteristics, as a function of thermal annealing parameters, indicates that a balancing is established. The balancing between charge conduction and excitonic dissociation leads to the establishment of optimal annealing conditions for maximized electronic performance. Additionally, the report highlights research areas that require attention for future development of this technology.