Naphthalene dithiol additive reduces trap-assisted recombination and improves outdoor operational stability of organic solar cells

While high efficiencies were achieved for organic photovoltaic (OPV) cells, the commercialization of this technology requires addressing the challenge of long-term device stability. The application of stabilizers is one of the promising approaches to suppress OPV degradation since it is inexpensive and easily scalable. However, only limited progress has been achieved in the development of such stabilizing additives. Herein, we proposed and practically evaluated naphthalene dithiol (NDT) as a promising stabilizing additive, which mimics the action of the natural glutathione system scavenging radicals and reactive oxygen species in animals. Using NDT did not lead to any significant drop in the characteristics of the assembled solar cells, whereas the operational stability was improved: the devices maintained more than 90% of their initial efficiency after 200 h of outdoor aging under real sunlight illumination in the Negev desert. A decrease in the non-geminate recombination has been achieved by reducing the number of traps and suppressing their formation in the course of device operation. These results suggest that using NDT as a stabilizing additive might facilitate the development of the OPV technology with the required long device operational lifetimes.