The Near Surface Morphology of P3HT:PCBM Blend Films Studied by Near-Edge X-Ray Absorption Fine Structure

The microstructure of poly(3-hexylthiophene) (P3HT) and 6,6-phenyl-C₆₁ butyric acid methyl ester (PCBM) blends with various annealing temperatures are investigated in detail by the near-edge x-ray absorption fine structure. Under higher annealing temperature (T_anneal≥160°C), P3HT shows an unusual fluidity and aggregation in the surface. After annealing, the enrichment polymer component recrystallizes and forms a single P3HT phase layer in the surface of blend films. Moreover, it gives direct evidence of the PCBM content diffusing to the near surface of blend films during annealing treatment. These findings are beneficial to improving the morphology of polymer/fullerene blend films.