Influence of Spin-coating Speed and Mixing Ratio on Polymer-Fullerene Films*

Due to increasing environmental concerns and depletion of nonrenewable resources, different forms of renewable energy must be studied. Organic solar cells are a very popular and promising form of renewable energy; however, they are still relatively new and not as well studied in comparison to traditional silicon solar cells. Thus, it is important to gain more knowledge on how those organic solar cells could be enhanced in different areas. Among the organic solar cells (OSC), OSC based on polymer-fullerene bulk heterojunctions have attracted much attention due to their low cost and easy processing conditions. The most common polymer-fullerene bulk heterojunction is poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM).
In this work, we show our studies on how the characteristics of P3HT:PCBM films depend on spin coating speed and mixing ratios. By varying the ratio of PCBM:P3HT as well as using different spin coating speeds, the impact on the absorbance spectrum of the films were studied. The results help us choose the optimum processing conditions for P3HT:PCBM films to be used in bulk heterojunction solar cells.