Composition depth profile analysis of bulk heterojunction layer by time-of-flight secondary ion mass spectrometry with gradient shaving preparation

Composition depth profile analysis of bulk heterojunction (BHJ) layer was performed by time-of-flight secondary ion mass spectrometry with gradient shaving preparation. The BHJ layer comprised of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61butyric acid methyl ester (PCBM) was formed on the substrate coated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) followed by annealing. The P3HT component increased toward the top surface in the BHJ layer. In addition, C8H7SO3− was detected inside the BHJ layer, suggesting penetration of PSS. P3HT was uniformly distributed in the BHJ layer without PEDOT:PSS. The P3HT-rich distribution in the top surface may be attributed to PSS penetration.