Performance Degradation of P3HT:PCBM Polymer/fullerene Photovoltaic Cells Under Gamma Irradiation

Organic photovoltaic cells are being considered for space applications due to the ease of fabrication, low production cost, and the potential to be used on flexible substrates. However, space-bound cells are exposed to high levels of radiation when orbiting the Earth. In this ongoing study, we examine the performance of P3HT:PCBM photovoltaic cells after exposure to gamma radiation from a cesium-137 source (662 keV). Preliminary results show degradation of the device I-V characteristics with radiation doses up to 5 krad. The integral mode time of flight (I-TOF) technique and current extraction by a linearly increasing voltage (CELIV) technique will be used to study the electron mobility and carrier lifetime properties as a function of the radiation dose. We speculate that main chain scission and reduced p-conjugation of P3HT are the dominant mechanisms responsible for performance degradation.