An Experimental Insight into the Reasons for Deterioration of P3HT:PCBM Bulk Heterojunction Solar Cells

In the present work, degradation mechanism in P3HT:PCBM bulk heterojunction photo-voltaic devices has been explored. For this purpose, the JV characteristics of eight P3HT:PCBM solar cell structures fabricated under identical conditions, were studied on hourly basis. Without exception, the power conversion efficiency (PCE) of the solar cells is found to fall off exponentially that saturates within six hours. The decay and rise time of the photo-current in the devices were also studied. The nature of the graphs negates the possibility of surface oxidation and generation of trap centers in the photo-active film. Thus, phase separation of P3HT and PCBM domains is expected to be the root cause of device degradation.