Thermal annealing effect on the morphology of inkjet printed polymer: Fullerene composites solar cells

One of critical factor in determining the performance of solar cells is the morphology of the active layer. The drying process of the active layer prepared by inkjet printing technique plays a key role in obtaining high quality surface morphology. This paper reports the effect of thermal annealing on the morphology of printed active layer. The printed active layer is a blend of poly(3-octylthiophene-2,5-diyl) and (6,6)-phenyl C71 butyric acid methyl ester dissolved in a mixture of dichlorobenzene:mesitylene. The printed films were then annealed at three different temperatures, namely 120, 140, and 160°C for 60 min to obtain the best performance of solar cells. It was found that the performance of solar cells strongly depends on the annealing temperature. The devices with the active layer annealed at 140°C exhibits the highest performance with short circuit current density and open circuit voltage as high as 2.88 μA/cm² and 0.85 V, respectively. The effect of annealing on the properties of printed active layer will be discussed.