Effect of Long Time Annealing and Incident Light Intensity on the Performance of Polymer: Fullerene Solar Cells

In this paper, we report the effect of long annealing time device and the influence of incident light intensity on the performance of polymer solar cells prepared using a Ca/Al top electrode and a blend film of regioregular poly(3-hexylthiophene) and soluble fullerene as a photoactive layer. Results showed that the device performance exhibited a four-stage trend with annealing time, which was attributed to the continuous change of nanomorphology in blend films. In particular, the longest time annealing (300 min) did not degrade the device performance, thus indicating durability of the thin Ca electrode. Interestingly, an extremely high fill factor (76%-82%) was obtained at a low light intensity.