Open circuit voltage decay as a tool to assess the reliability of organic solar cells: P3HT:PCBM vs. HBG1:PCBM

We developed a model that explain the open circuit voltage decay in polymeric solar cells to analyze the effects of the degradation induced by accelerated life-tests. The model accounts for the polaron pairs separation and recombination, the Langevin recombination, and the trap assisted recombination. The model permits to calculate several parameters. Among them, for the first time, we were able to extrapolate the Energy Gap of the blend from electrical, non-destructive measurements. We performed electrical stresses on organic solar cells based on two different active layers (P3HT:PC61BM, HBG1:PC61BM) applying specific characterizations, including open circuit voltage decay. We showed the better reliability of HBG1 based devices with respect to the analogous systems containing P3HT as donor material.