Correlation Between Structural and Optical Properties of Composite Polymer/Fullerene Films for Organic Solar Cells

• Published in: Advanced functional materials Vol. 15; no. 7; pp. 1193 - 1196
• Main Authors: Erb, T., Zhokhavets, U., Gobsch, G., Raleva, S., Stühn, B., Schilinsky, P., Waldauf, C., Brabec, C. J.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01-07-2005; WILEY‐VCH Verlag
• Subjects: Polymer films; Polythiophenes; Solar cells
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200400521

We investigate thin poly(3‐hexylthiophene‐2,5‐diyl)/[6,6]‐phenyl C61 butyric acid methyl ester (P3HT/PCBM) films, which are widely used as active layers in plastic solar cells. Their structural properties are studied by grazing‐incidence X‐ray diffraction (XRD). The size and the orientation of crystalline P3HT nanodomains within the films are determined. PCBM crystallites are not detected in thin films by XRD. Upon annealing, the P3HT crystallinity increases, leading to an increase in the optical absorption and spectral photocurrent in the low‐photon‐energy region. As a consequence, the efficiency of P3HT/PCBM solar cells is significantly increased. A direct relation between efficiency and P3HT crystallinity is demonstrated.
Structural properties of films of poly‐ [3‐hexylthiophene‐2,5‐diyl]/[6,6]‐phenyl C61 butyric acid methyl ester (P3HT/PCBM) have been studied by X‐ray diffraction. P3HT crystallites with a‐axis orientation (see Figure) were observed, whereas PCBM crystallites were not found. The influence of P3HT crystallinity on the performance of P3HT/PCBM solar cells is discussed.