Center for Relativistic Laser Science

2018 121st KCS General Meeting

Organic photovoltaic(OPV) is in the spotlight as a component of solar cell because of its lower cost fabrication and better processability compared with existing silicon. Materials of OPV have been studied to improve power conversion efficiency(PCE) and PTB7-Th polymer is suitable to gain high PCE. However, photodegradation of PTB7-Th polymer is one of the significant obstacles in the pursuit of commercializing OPV as solar cell component. Since PTB7-Th polymer can be photodegraded, it causes OPV to have lower stability in ambient condition. Therefore, it is required to find photodegradation process and its major factor impacting photodegradation. In this research, we used home-built Raman spectroscopic setup to study photodegradation process of PTB7-Th on a molecular level. DFT calculation was used to find plausible photodegradation product. As a result, we conclude that changes in Raman spectrum resulted from generation of hydroxyl group(-OH) at BDT unit and S=O bond at TT unit. We went further and suggested feasible photodegradation mechanism. This research will be conducive to preventing those generations and allow us to gain efficient OPV with high stability.