LIFETIME STUDY OF ORGANIC PHOTOVOLTAIC MATERIALS THROUGH OUTDOOR TESTS

Resumo

Organic photovoltaics (OPV) have undergone a significant development in recent years, with companies reaching efficiencies above 13%. Its unique features of transparency, light weight and flexibility allow the OPV application where conventional photovoltaics reach their limits, such as building integrated photovoltaics (BIPV). Many projects are emerging for this type of application, such as façade integration, and it is important to guarantee that the lifetime of the OPV devices is similar to what it is being integrated to. As a relatively recent technology, there are not many studies focusing on the stability and lifetime of OPV and even though standard tests have been defined for means of comparison of technology development, there are no appropriate qualification tests to assure the durability of the modules. As accelerated tests are not yet correlated to real operational conditions either, outdoor tests are a must to study degradation behaviors and pathways to improve the lifetime. In this paper, outdoor tests have been conducted for a period over a year to compare different photoactive materials and assess their stability under operational conditions. By the use of an in-house built software, the current-voltage measurements performed along the day hours were used to build degradation curves and model the energy generated over time. Differences in degradation rate were observed for the three polymers tested, as well as a relation between irradiation levels and the performance and stability of the devices.